From c01690fcb941ab8d5c21183143b4320f006c2d4c Mon Sep 17 00:00:00 2001
From: Abhimanyu Singh Gaur
 <12651351+abhimanyusinghgaur@users.noreply.github.com>
Date: Tue, 6 Oct 2020 16:07:15 +0530
Subject: [PATCH] feat(GraphQL): GraphQL now has lambda resolvers (#6574)

This PR adds `@lambda` directive in GraphQL, using which one can call Custom JavaScript resolvers. Now, alpha has a flag called `--graphql_lambda_url` which is used to set the URL of the lambda server. All the `@lambda` fields will be resolved through the lambda functions implemented on the given lambda server.

RFC: https://discuss.dgraph.io/t/implement-custom-js-resolvers-in-graphql/9361
Lambda server: https://github.com/dgraph-io/dgraph-lambda

(cherry picked from commit 2f3d7f4fafc24255cb9e5706c066596b40e28569)

# Conflicts:
#	graphql/e2e/common/common.go
#	graphql/e2e/directives/docker-compose.yml
#	graphql/e2e/directives/schema.graphql
#	graphql/e2e/normal/docker-compose.yml
#	graphql/e2e/normal/schema.graphql
#	graphql/e2e/schema/generatedSchema.graphql
#	graphql/schema/gqlschema.go
#	graphql/schema/testdata/schemagen/output/authorization.graphql
#	graphql/schema/testdata/schemagen/output/comments-and-descriptions.graphql
#	graphql/schema/testdata/schemagen/output/custom-mutation.graphql
#	graphql/schema/testdata/schemagen/output/custom-nested-types.graphql
#	graphql/schema/testdata/schemagen/output/custom-query-mixed-types.graphql
#	graphql/schema/testdata/schemagen/output/custom-query-not-dgraph-type.graphql
#	graphql/schema/testdata/schemagen/output/custom-query-with-dgraph-type.graphql
#	graphql/schema/testdata/schemagen/output/deprecated.graphql
#	graphql/schema/testdata/schemagen/output/dgraph-reverse-directive-on-concrete-type-with-interfaces.graphql
#	graphql/schema/testdata/schemagen/output/dgraph-reverse-directive-with-interfaces.graphql
#	graphql/schema/testdata/schemagen/output/field-with-id-directive.graphql
#	graphql/schema/testdata/schemagen/output/field-with-reverse-predicate-in-dgraph-directive.graphql
#	graphql/schema/testdata/schemagen/output/filter-cleanSchema-directLink.graphql
#	graphql/schema/testdata/schemagen/output/hasInverse-with-interface-having-directive.graphql
#	graphql/schema/testdata/schemagen/output/hasInverse-with-interface.graphql
#	graphql/schema/testdata/schemagen/output/hasInverse-with-type-having-directive.graphql
#	graphql/schema/testdata/schemagen/output/hasInverse.graphql
#	graphql/schema/testdata/schemagen/output/hasInverse_withSubscription.graphql
#	graphql/schema/testdata/schemagen/output/ignore-unsupported-directive.graphql
#	graphql/schema/testdata/schemagen/output/interface-with-dgraph-pred.graphql
#	graphql/schema/testdata/schemagen/output/interface-with-id-directive.graphql
#	graphql/schema/testdata/schemagen/output/interface-with-no-ids.graphql
#	graphql/schema/testdata/schemagen/output/interfaces-with-types-and-password.graphql
#	graphql/schema/testdata/schemagen/output/interfaces-with-types.graphql
#	graphql/schema/testdata/schemagen/output/no-id-field-with-searchables.graphql
#	graphql/schema/testdata/schemagen/output/no-id-field.graphql
#	graphql/schema/testdata/schemagen/output/password-type.graphql
#	graphql/schema/testdata/schemagen/output/searchables-references.graphql
#	graphql/schema/testdata/schemagen/output/searchables.graphql
#	graphql/schema/testdata/schemagen/output/single-type-with-enum.graphql
#	graphql/schema/testdata/schemagen/output/single-type.graphql
#	graphql/schema/testdata/schemagen/output/type-implements-multiple-interfaces.graphql
#	graphql/schema/testdata/schemagen/output/type-reference.graphql
#	graphql/schema/testdata/schemagen/output/type-with-arguments-on-field.graphql
#	graphql/schema/testdata/schemagen/output/type-with-custom-field-on-dgraph-type.graphql
#	graphql/schema/testdata/schemagen/output/type-with-custom-fields-on-remote-type.graphql
#	graphql/schema/testdata/schemagen/output/type-without-orderables.graphql
---
 dgraph/cmd/alpha/run.go                       |  16 ++
 graphql/authorization/auth.go                 |  12 +
 graphql/e2e/common/common.go                  |   5 +
 graphql/e2e/common/lambda.go                  | 197 ++++++++++++++
 graphql/e2e/common/schema.go                  |   8 +
 graphql/e2e/custom_logic/cmd/main.go          |   5 +
 graphql/e2e/custom_logic/custom_logic_test.go |   4 +-
 .../e2e/directives/dgraph_directives_test.go  |   5 +
 graphql/e2e/directives/docker-compose.yml     |  24 +-
 graphql/e2e/directives/schema.graphql         |  13 +-
 graphql/e2e/directives/script.js              |  51 ++++
 graphql/e2e/normal/docker-compose.yml         |  24 +-
 graphql/e2e/normal/normal_test.go             |   5 +
 graphql/e2e/normal/schema.graphql             |  13 +-
 graphql/e2e/normal/script.js                  |  51 ++++
 graphql/e2e/schema/generatedSchema.graphql    |   1 +
 graphql/resolve/custom_mutation_test.yaml     |   4 +-
 graphql/resolve/custom_query_test.yaml        |   3 +-
 graphql/resolve/resolver.go                   |  42 ++-
 graphql/schema/dgraph_schemagen_test.yml      |  19 +-
 graphql/schema/gqlschema.go                   |  50 ++--
 graphql/schema/gqlschema_test.yml             |  28 +-
 graphql/schema/rules.go                       |  67 +++--
 graphql/schema/schemagen.go                   |   2 +-
 graphql/schema/schemagen_test.go              |   8 +
 .../schemagen/input/lambda-directive.graphql  |  14 +
 .../schemagen/output/authorization.graphql    |   1 +
 .../output/comments-and-descriptions.graphql  |   1 +
 .../schemagen/output/custom-mutation.graphql  |   1 +
 .../output/custom-nested-types.graphql        |   1 +
 .../output/custom-query-mixed-types.graphql   |   1 +
 .../custom-query-not-dgraph-type.graphql      |   1 +
 .../custom-query-with-dgraph-type.graphql     |   1 +
 .../schemagen/output/deprecated.graphql       |   1 +
 ...e-on-concrete-type-with-interfaces.graphql |   1 +
 ...-reverse-directive-with-interfaces.graphql |   1 +
 .../output/field-with-id-directive.graphql    |   1 +
 ...erse-predicate-in-dgraph-directive.graphql |   1 +
 .../filter-cleanSchema-directLink.graphql     |   1 +
 ...se-with-interface-having-directive.graphql |   1 +
 .../output/hasInverse-with-interface.graphql  |   1 +
 ...Inverse-with-type-having-directive.graphql |   1 +
 .../schemagen/output/hasInverse.graphql       |   1 +
 .../hasInverse_withSubscription.graphql       |   1 +
 .../ignore-unsupported-directive.graphql      |   1 +
 .../output/interface-with-dgraph-pred.graphql |   1 +
 .../interface-with-id-directive.graphql       |   1 +
 .../output/interface-with-no-ids.graphql      |   1 +
 ...interfaces-with-types-and-password.graphql |   1 +
 .../output/interfaces-with-types.graphql      |   1 +
 .../schemagen/output/lambda-directive.graphql | 245 ++++++++++++++++++
 .../no-id-field-with-searchables.graphql      |   1 +
 .../schemagen/output/no-id-field.graphql      |   1 +
 .../schemagen/output/password-type.graphql    |   1 +
 .../output/searchables-references.graphql     |   1 +
 .../schemagen/output/searchables.graphql      |   1 +
 .../output/single-type-with-enum.graphql      |   1 +
 .../schemagen/output/single-type.graphql      |   1 +
 ...ype-implements-multiple-interfaces.graphql |   1 +
 .../schemagen/output/type-reference.graphql   |   1 +
 .../type-with-arguments-on-field.graphql      |   1 +
 ...e-with-custom-field-on-dgraph-type.graphql |   2 +-
 ...-with-custom-fields-on-remote-type.graphql |   2 +-
 .../output/type-without-orderables.graphql    |   1 +
 graphql/schema/wrappers.go                    | 179 ++++++++++++-
 x/config.go                                   |   2 +
 66 files changed, 1042 insertions(+), 94 deletions(-)
 create mode 100644 graphql/e2e/common/lambda.go
 create mode 100644 graphql/e2e/directives/script.js
 create mode 100644 graphql/e2e/normal/script.js
 create mode 100644 graphql/schema/testdata/schemagen/input/lambda-directive.graphql
 create mode 100644 graphql/schema/testdata/schemagen/output/lambda-directive.graphql

diff --git a/dgraph/cmd/alpha/run.go b/dgraph/cmd/alpha/run.go
index 3eaf3ab3a78..66bbb5c222b 100644
--- a/dgraph/cmd/alpha/run.go
+++ b/dgraph/cmd/alpha/run.go
@@ -27,6 +27,7 @@ import (
 	"net"
 	"net/http"
 	_ "net/http/pprof" // http profiler
+	"net/url"
 	"os"
 	"os/signal"
 	"strings"
@@ -212,6 +213,8 @@ they form a Raft group and provide synchronous replication.
 	flag.Bool("ludicrous_mode", false, "Run alpha in ludicrous mode")
 	flag.Bool("graphql_extensions", true, "Set to false if extensions not required in GraphQL response body")
 	flag.Duration("graphql_poll_interval", time.Second, "polling interval for graphql subscription.")
+	flag.String("graphql_lambda_url", "",
+		"URL of lambda server that implements custom GraphQL JavaScript resolvers")
 
 	// Cache flags
 	flag.Int64("cache_mb", 0, "Total size of cache (in MB) to be used in alpha.")
@@ -725,6 +728,19 @@ func run() {
 	x.Config.PollInterval = Alpha.Conf.GetDuration("graphql_poll_interval")
 	x.Config.GraphqlExtension = Alpha.Conf.GetBool("graphql_extensions")
 	x.Config.GraphqlDebug = Alpha.Conf.GetBool("graphql_debug")
+	x.Config.GraphqlLambdaUrl = Alpha.Conf.GetString("graphql_lambda_url")
+	if x.Config.GraphqlLambdaUrl != "" {
+		graphqlLambdaUrl, err := url.Parse(x.Config.GraphqlLambdaUrl)
+		if err != nil {
+			glog.Errorf("unable to parse graphql_lambda_url: %v", err)
+			return
+		}
+		if !graphqlLambdaUrl.IsAbs() {
+			glog.Errorf("expecting graphql_lambda_url to be an absolute URL, got: %s",
+				graphqlLambdaUrl.String())
+			return
+		}
+	}
 
 	x.PrintVersion()
 	glog.Infof("x.Config: %+v", x.Config)
diff --git a/graphql/authorization/auth.go b/graphql/authorization/auth.go
index 849b54b45d1..3fb2bcc5fd8 100644
--- a/graphql/authorization/auth.go
+++ b/graphql/authorization/auth.go
@@ -252,6 +252,18 @@ func ExtractCustomClaims(ctx context.Context) (*CustomClaims, error) {
 	return validateJWTCustomClaims(jwtToken[0])
 }
 
+func GetJwtToken(ctx context.Context) string {
+	md, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return ""
+	}
+	jwtToken := md.Get(string(AuthJwtCtxKey))
+	if len(jwtToken) != 1 {
+		return ""
+	}
+	return jwtToken[0]
+}
+
 func validateJWTCustomClaims(jwtStr string) (*CustomClaims, error) {
 	if metainfo.Algo == "" {
 		return nil, fmt.Errorf(
diff --git a/graphql/e2e/common/common.go b/graphql/e2e/common/common.go
index fb925115cd1..d42b512130e 100644
--- a/graphql/e2e/common/common.go
+++ b/graphql/e2e/common/common.go
@@ -385,6 +385,11 @@ func RunAll(t *testing.T) {
 	t.Run("fragment in query on Interface", fragmentInQueryOnInterface)
 	t.Run("fragment in query on Object", fragmentInQueryOnObject)
 
+	// lambda tests
+	t.Run("lambda on type field", lambdaOnTypeField)
+	t.Run("lambda on interface field", lambdaOnInterfaceField)
+	t.Run("lambda on query using dql", lambdaOnQueryUsingDql)
+	t.Run("lambda on mutation using graphql", lambdaOnMutationUsingGraphQL)
 }
 
 // RunCorsTest test all cors related tests.
diff --git a/graphql/e2e/common/lambda.go b/graphql/e2e/common/lambda.go
new file mode 100644
index 00000000000..ee9f1d3210a
--- /dev/null
+++ b/graphql/e2e/common/lambda.go
@@ -0,0 +1,197 @@
+/*
+ * Copyright 2020 Dgraph Labs, Inc. and Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package common
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/dgraph-io/dgraph/testutil"
+)
+
+func lambdaOnTypeField(t *testing.T) {
+	query := `
+		query {
+			queryAuthor {
+				name
+				bio
+				rank
+			}
+		}`
+	params := &GraphQLParams{Query: query}
+	resp := params.ExecuteAsPost(t, GraphqlURL)
+	RequireNoGQLErrors(t, resp)
+
+	expectedResponse := `{
+		"queryAuthor": [
+			{
+				"name":"Three Author",
+				"bio":"My name is Three Author and I was born on 2001-01-01T00:00:00Z.",
+				"rank":1
+			},
+			{
+				"name":"Ann Author",
+				"bio":"My name is Ann Author and I was born on 2000-01-01T00:00:00Z.",
+				"rank":3
+			},
+			{
+				"name":"Ann Other Author",
+				"bio":"My name is Ann Other Author and I was born on 1988-01-01T00:00:00Z.",
+				"rank":2
+			}
+		]
+	}`
+	testutil.CompareJSON(t, expectedResponse, string(resp.Data))
+}
+
+func lambdaOnInterfaceField(t *testing.T) {
+	starship := addStarship(t)
+	humanID := addHuman(t, starship.ID)
+	droidID := addDroid(t)
+
+	// when querying bio on Character (interface) we should get the bio constructed by the lambda
+	// registered on Character.bio
+	query := `
+		query {
+			queryCharacter {
+				name
+				bio
+			}
+		}`
+	params := &GraphQLParams{Query: query}
+	resp := params.ExecuteAsPost(t, GraphqlURL)
+	RequireNoGQLErrors(t, resp)
+
+	expectedResponse := `{
+		"queryCharacter": [
+			{
+				"name":"Han",
+				"bio":"My name is Han."
+			},
+			{
+				"name":"R2-D2",
+				"bio":"My name is R2-D2."
+			}
+		]
+	}`
+	testutil.CompareJSON(t, expectedResponse, string(resp.Data))
+
+	// TODO: this should work. At present there is a bug with @custom on interface field resolved
+	// through a fragment on one of its types. We need to fix that first, then uncomment this test.
+
+	// when querying bio on Human & Droid (type) we should get the bio constructed by the lambda
+	// registered on Human.bio and Droid.bio respectively
+	/*query = `
+		query {
+			queryCharacter {
+				name
+				... on Human {
+					bio
+				}
+				... on Droid {
+					bio
+				}
+			}
+		}`
+	params = &GraphQLParams{Query: query}
+	resp = params.ExecuteAsPost(t, GraphqlURL)
+	RequireNoGQLErrors(t, resp)
+
+	expectedResponse = `{
+		"queryCharacter": [
+			{
+				"name":"Han",
+				"bio":"My name is Han. I have 10 credits."
+			},
+			{
+				"name":"R2-D2",
+				"bio":"My name is R2-D2. My primary function is Robot."
+			}
+		]
+	}`
+	testutil.CompareJSON(t, expectedResponse, string(resp.Data))*/
+
+	// cleanup
+	cleanupStarwars(t, starship.ID, humanID, droidID)
+}
+
+func lambdaOnQueryUsingDql(t *testing.T) {
+	query := `
+		query {
+			authorsByName(name: "Ann Author") {
+				name
+				dob
+				reputation
+			}
+		}`
+	params := &GraphQLParams{Query: query}
+	resp := params.ExecuteAsPost(t, GraphqlURL)
+	RequireNoGQLErrors(t, resp)
+
+	expectedResponse := `{
+		"authorsByName": [
+			{
+				"name":"Ann Author",
+				"dob":"2000-01-01T00:00:00Z",
+				"reputation":6.6
+			}
+		]
+	}`
+	testutil.CompareJSON(t, expectedResponse, string(resp.Data))
+}
+
+func lambdaOnMutationUsingGraphQL(t *testing.T) {
+	// first, add the author using @lambda
+	query := `
+		mutation {
+			newAuthor(name: "Lambda")
+		}`
+	params := &GraphQLParams{Query: query}
+	resp := params.ExecuteAsPost(t, GraphqlURL)
+	RequireNoGQLErrors(t, resp)
+
+	// let's get the author ID of the newly added author as returned by lambda
+	var addResp struct {
+		AuthorID string `json:"newAuthor"`
+	}
+	require.NoError(t, json.Unmarshal(resp.Data, &addResp))
+
+	// now, lets query the same author and verify that its reputation was set as 3.0 by lambda func
+	query = `
+		query ($id: ID!){
+			getAuthor(id: $id) {
+				name
+				reputation
+			}
+		}`
+	params = &GraphQLParams{Query: query, Variables: map[string]interface{}{"id": addResp.AuthorID}}
+	resp = params.ExecuteAsPost(t, GraphqlURL)
+	RequireNoGQLErrors(t, resp)
+
+	expectedResponse := `{
+		"getAuthor": {
+				"name":"Lambda",
+				"reputation":3.0
+			}
+	}`
+	testutil.CompareJSON(t, expectedResponse, string(resp.Data))
+
+	// cleanup
+	deleteAuthors(t, []string{addResp.AuthorID}, nil)
+}
diff --git a/graphql/e2e/common/schema.go b/graphql/e2e/common/schema.go
index ebccc782792..5cd6b8b5d93 100644
--- a/graphql/e2e/common/schema.go
+++ b/graphql/e2e/common/schema.go
@@ -74,6 +74,14 @@ const (
             {
                 "name": "posts",
 				"description": ""
+            },
+            {
+                "name": "bio",
+				"description": ""
+            },
+            {
+                "name": "rank",
+				"description": ""
             }
 		],
 		"enumValues":[]
diff --git a/graphql/e2e/custom_logic/cmd/main.go b/graphql/e2e/custom_logic/cmd/main.go
index 5d2c8254661..939b0bd0bf9 100644
--- a/graphql/e2e/custom_logic/cmd/main.go
+++ b/graphql/e2e/custom_logic/cmd/main.go
@@ -141,6 +141,11 @@ func compareHeaders(headers map[string][]string, actual http.Header) error {
 	if headers == nil {
 		return nil
 	}
+	// unless some other content-type was expected, always make sure we get JSON as content-type.
+	if _, ok := headers["Content-Type"]; !ok {
+		headers["Content-Type"] = []string{"application/json"}
+	}
+
 	actualHeaderLen := len(actual)
 	expectedHeaderLen := len(headers)
 	if actualHeaderLen != expectedHeaderLen {
diff --git a/graphql/e2e/custom_logic/custom_logic_test.go b/graphql/e2e/custom_logic/custom_logic_test.go
index b70c44f9a2d..ac91ad67af8 100644
--- a/graphql/e2e/custom_logic/custom_logic_test.go
+++ b/graphql/e2e/custom_logic/custom_logic_test.go
@@ -230,7 +230,7 @@ func TestCustomQueryShouldForwardHeaders(t *testing.T) {
 	}
 
 	result := params.ExecuteAsPost(t, alphaURL)
-	require.Nil(t, result.Errors)
+	require.Nilf(t, result.Errors, "%s", result.Errors)
 	expected := `{"verifyHeaders":[{"id":"0x3","name":"Star Wars"}]}`
 	require.Equal(t, expected, string(result.Data))
 }
@@ -269,7 +269,7 @@ func TestCustomNameForwardHeaders(t *testing.T) {
 	}
 
 	result := params.ExecuteAsPost(t, alphaURL)
-	require.Nil(t, result.Errors)
+	require.Nilf(t, result.Errors, "%s", result.Errors)
 	expected := `{"verifyHeaders":[{"id":"0x3","name":"Star Wars"}]}`
 	require.Equal(t, expected, string(result.Data))
 }
diff --git a/graphql/e2e/directives/dgraph_directives_test.go b/graphql/e2e/directives/dgraph_directives_test.go
index 82a15bd5eec..3eeaca3174b 100644
--- a/graphql/e2e/directives/dgraph_directives_test.go
+++ b/graphql/e2e/directives/dgraph_directives_test.go
@@ -21,6 +21,8 @@ import (
 	"os"
 	"testing"
 
+	"github.com/dgraph-io/dgraph/x"
+
 	"github.com/dgraph-io/dgraph/graphql/e2e/common"
 	"github.com/pkg/errors"
 	"github.com/stretchr/testify/require"
@@ -54,6 +56,9 @@ func TestMain(m *testing.M) {
 		panic(errors.Wrapf(err, "Unable to read file %s.", jsonFile))
 	}
 
+	// set up the lambda url for unit tests
+	x.Config.GraphqlLambdaUrl = "http://localhost:8086/graphql-worker"
+
 	common.BootstrapServer(schema, data)
 
 	os.Exit(m.Run())
diff --git a/graphql/e2e/directives/docker-compose.yml b/graphql/e2e/directives/docker-compose.yml
index 154fc96fb3a..2cc6fee3efd 100644
--- a/graphql/e2e/directives/docker-compose.yml
+++ b/graphql/e2e/directives/docker-compose.yml
@@ -32,7 +32,10 @@ services:
     labels:
       cluster: test
       service: alpha1
-    command: /gobin/dgraph alpha --lru_mb=1024 --zero=zero1:5180 -o 100 --expose_trace --trace 1.0 --profile_mode block --block_rate 10 --logtostderr -v=2 --whitelist 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16 --my=alpha1:7180
+    command: /gobin/dgraph alpha --lru_mb=1024 --zero=zero1:5180 -o 100 --expose_trace --trace 1.0
+      --profile_mode block --block_rate 10 --logtostderr -v=2
+      --whitelist 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16 --my=alpha1:7180
+      --graphql_lambda_url=http://lambda:8686/graphql-worker
 
   zeroAdmin:
     image: dgraph/dgraph:latest
@@ -66,4 +69,21 @@ services:
     labels:
       cluster: admintest
       service: alphaAdmin
-    command: /gobin/dgraph alpha --lru_mb=1024 --zero=zeroAdmin:5280 -o 200 --expose_trace --trace 1.0 --profile_mode block --block_rate 10 --logtostderr -v=2 --whitelist 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16 --my=alphaAdmin:7280
\ No newline at end of file
+    command: /gobin/dgraph alpha --lru_mb=1024 --zero=zeroAdmin:5280 -o 200 --expose_trace --trace 1.0 --profile_mode block --block_rate 10 --logtostderr -v=2 --whitelist 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16 --my=alphaAdmin:7280
+
+  lambda:
+    image: dgraph/dgraph-lambda:latest
+    container_name: lambda
+    labels:
+      cluster: test
+    ports:
+      - 8686:8686
+    depends_on:
+      - alpha
+    environment:
+      DGRAPH_URL: http://alpha:8180
+    volumes:
+      - type: bind
+        source: ./script.js
+        target: /app/script.js
+        read_only: true
\ No newline at end of file
diff --git a/graphql/e2e/directives/schema.graphql b/graphql/e2e/directives/schema.graphql
index f6406d00f87..1f750edeef3 100644
--- a/graphql/e2e/directives/schema.graphql
+++ b/graphql/e2e/directives/schema.graphql
@@ -37,6 +37,8 @@ type Author @dgraph(type: "test.dgraph.author") {
         reputation: Float @search
         country: Country
         posts: [Post!] @hasInverse(field: author)
+		bio: String @lambda
+		rank: Int @lambda
 }
 
 type Post @dgraph(type: "myPost") {
@@ -89,6 +91,7 @@ interface Character @dgraph(type: "performance.character") {
         id: ID!
         name: String! @search(by: [exact])
         appearsIn: [Episode!] @search @dgraph(pred: "appears_in")
+		bio: String @lambda
 }
 
 type Human implements Character & Employee {
@@ -177,4 +180,12 @@ type Person1 {
 	id: ID!
 	name: String!
 	friends: [Person1] @hasInverse(field: friends)
-}
\ No newline at end of file
+}
+
+type Query {
+	authorsByName(name: String!): [Author] @lambda
+}
+
+type Mutation {
+	newAuthor(name: String!): ID! @lambda
+}
diff --git a/graphql/e2e/directives/script.js b/graphql/e2e/directives/script.js
new file mode 100644
index 00000000000..324c009264e
--- /dev/null
+++ b/graphql/e2e/directives/script.js
@@ -0,0 +1,51 @@
+const authorBio = ({parent: {name, dob}}) => `My name is ${name} and I was born on ${dob}.`
+const characterBio = ({parent: {name}}) => `My name is ${name}.`
+const humanBio = ({parent: {name, totalCredits}}) => `My name is ${name}. I have ${totalCredits} credits.`
+const droidBio = ({parent: {name, primaryFunction}}) => `My name is ${name}. My primary function is ${primaryFunction}.`
+
+async function authorsByName({args, dql}) {
+    const results = await dql.query(`query queryAuthor($name: string) {
+        queryAuthor(func: type(test.dgraph.author)) @filter(eq(test.dgraph.author.name, $name)) {
+            name: test.dgraph.author.name
+            dob: test.dgraph.author.dob
+            reputation: test.dgraph.author.reputation
+        }
+    }`, {"$name": args.name})
+    return results.data.queryAuthor
+}
+
+async function newAuthor({args, graphql}) {
+    // lets give every new author a reputation of 3 by default
+    const results = await graphql(`mutation ($name: String!) {
+        addAuthor(input: [{name: $name, reputation: 3.0 }]) {
+            author {
+                id
+                reputation
+            }
+        }
+    }`, {"name": args.name})
+    return results.data.addAuthor.author[0].id
+}
+
+self.addGraphQLResolvers({
+    "Author.bio": authorBio,
+    "Character.bio": characterBio,
+    "Human.bio": humanBio,
+    "Droid.bio": droidBio,
+    "Query.authorsByName": authorsByName,
+    "Mutation.newAuthor": newAuthor
+})
+
+async function rank({parents}) {
+    const idRepList = parents.map(function (parent) {
+        return {id: parent.id, rep: parent.reputation}
+    });
+    const idRepMap = {};
+    idRepList.sort((a, b) => a.rep > b.rep ? -1 : 1)
+        .forEach((a, i) => idRepMap[a.id] = i + 1)
+    return parents.map(p => idRepMap[p.id])
+}
+
+self.addMultiParentGraphQLResolvers({
+    "Author.rank": rank
+})
\ No newline at end of file
diff --git a/graphql/e2e/normal/docker-compose.yml b/graphql/e2e/normal/docker-compose.yml
index 154fc96fb3a..2cc6fee3efd 100644
--- a/graphql/e2e/normal/docker-compose.yml
+++ b/graphql/e2e/normal/docker-compose.yml
@@ -32,7 +32,10 @@ services:
     labels:
       cluster: test
       service: alpha1
-    command: /gobin/dgraph alpha --lru_mb=1024 --zero=zero1:5180 -o 100 --expose_trace --trace 1.0 --profile_mode block --block_rate 10 --logtostderr -v=2 --whitelist 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16 --my=alpha1:7180
+    command: /gobin/dgraph alpha --lru_mb=1024 --zero=zero1:5180 -o 100 --expose_trace --trace 1.0
+      --profile_mode block --block_rate 10 --logtostderr -v=2
+      --whitelist 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16 --my=alpha1:7180
+      --graphql_lambda_url=http://lambda:8686/graphql-worker
 
   zeroAdmin:
     image: dgraph/dgraph:latest
@@ -66,4 +69,21 @@ services:
     labels:
       cluster: admintest
       service: alphaAdmin
-    command: /gobin/dgraph alpha --lru_mb=1024 --zero=zeroAdmin:5280 -o 200 --expose_trace --trace 1.0 --profile_mode block --block_rate 10 --logtostderr -v=2 --whitelist 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16 --my=alphaAdmin:7280
\ No newline at end of file
+    command: /gobin/dgraph alpha --lru_mb=1024 --zero=zeroAdmin:5280 -o 200 --expose_trace --trace 1.0 --profile_mode block --block_rate 10 --logtostderr -v=2 --whitelist 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16 --my=alphaAdmin:7280
+
+  lambda:
+    image: dgraph/dgraph-lambda:latest
+    container_name: lambda
+    labels:
+      cluster: test
+    ports:
+      - 8686:8686
+    depends_on:
+      - alpha
+    environment:
+      DGRAPH_URL: http://alpha:8180
+    volumes:
+      - type: bind
+        source: ./script.js
+        target: /app/script.js
+        read_only: true
\ No newline at end of file
diff --git a/graphql/e2e/normal/normal_test.go b/graphql/e2e/normal/normal_test.go
index a4ac2f0948d..0dbe13d79c0 100644
--- a/graphql/e2e/normal/normal_test.go
+++ b/graphql/e2e/normal/normal_test.go
@@ -21,6 +21,8 @@ import (
 	"os"
 	"testing"
 
+	"github.com/dgraph-io/dgraph/x"
+
 	"github.com/dgraph-io/dgraph/graphql/e2e/common"
 	"github.com/pkg/errors"
 	"github.com/stretchr/testify/require"
@@ -53,6 +55,9 @@ func TestMain(m *testing.M) {
 		panic(errors.Wrapf(err, "Unable to read file %s.", jsonFile))
 	}
 
+	// set up the lambda url for unit tests
+	x.Config.GraphqlLambdaUrl = "http://localhost:8086/graphql-worker"
+
 	common.BootstrapServer(schema, data)
 
 	os.Exit(m.Run())
diff --git a/graphql/e2e/normal/schema.graphql b/graphql/e2e/normal/schema.graphql
index fe2675a3244..7e5fb18270f 100644
--- a/graphql/e2e/normal/schema.graphql
+++ b/graphql/e2e/normal/schema.graphql
@@ -37,6 +37,8 @@ type Author {
         reputation: Float @search
         country: Country
         posts: [Post!] @hasInverse(field: author)
+        bio: String @lambda
+        rank: Int @lambda
 }
 
 type Post {
@@ -89,6 +91,7 @@ interface Character {
         id: ID!
         name: String! @search(by: [exact])
         appearsIn: [Episode!] @search
+        bio: String @lambda
 }
 
 type Human implements Character & Employee {
@@ -177,4 +180,12 @@ type Person1 {
         id: ID!
         name: String!
         friends: [Person1] @hasInverse(field: friends)
-}
\ No newline at end of file
+}
+
+type Query {
+        authorsByName(name: String!): [Author] @lambda
+}
+
+type Mutation {
+        newAuthor(name: String!): ID! @lambda
+}
diff --git a/graphql/e2e/normal/script.js b/graphql/e2e/normal/script.js
new file mode 100644
index 00000000000..dcfd429ec34
--- /dev/null
+++ b/graphql/e2e/normal/script.js
@@ -0,0 +1,51 @@
+const authorBio = ({parent: {name, dob}}) => `My name is ${name} and I was born on ${dob}.`
+const characterBio = ({parent: {name}}) => `My name is ${name}.`
+const humanBio = ({parent: {name, totalCredits}}) => `My name is ${name}. I have ${totalCredits} credits.`
+const droidBio = ({parent: {name, primaryFunction}}) => `My name is ${name}. My primary function is ${primaryFunction}.`
+
+async function authorsByName({args, dql}) {
+    const results = await dql.query(`query queryAuthor($name: string) {
+        queryAuthor(func: type(Author)) @filter(eq(Author.name, $name)) {
+            name: Author.name
+            dob: Author.dob
+            reputation: Author.reputation
+        }
+    }`, {"$name": args.name})
+    return results.data.queryAuthor
+}
+
+async function newAuthor({args, graphql}) {
+    // lets give every new author a reputation of 3 by default
+    const results = await graphql(`mutation ($name: String!) {
+        addAuthor(input: [{name: $name, reputation: 3.0 }]) {
+            author {
+                id
+                reputation
+            }
+        }
+    }`, {"name": args.name})
+    return results.data.addAuthor.author[0].id
+}
+
+self.addGraphQLResolvers({
+    "Author.bio": authorBio,
+    "Character.bio": characterBio,
+    "Human.bio": humanBio,
+    "Droid.bio": droidBio,
+    "Query.authorsByName": authorsByName,
+    "Mutation.newAuthor": newAuthor
+})
+
+async function rank({parents}) {
+    const idRepList = parents.map(function (parent) {
+        return {id: parent.id, rep: parent.reputation}
+    });
+    const idRepMap = {};
+    idRepList.sort((a, b) => a.rep > b.rep ? -1 : 1)
+        .forEach((a, i) => idRepMap[a.id] = i + 1)
+    return parents.map(p => idRepMap[p.id])
+}
+
+self.addMultiParentGraphQLResolvers({
+    "Author.rank": rank
+})
\ No newline at end of file
diff --git a/graphql/e2e/schema/generatedSchema.graphql b/graphql/e2e/schema/generatedSchema.graphql
index 38d895ca8ab..0b624a3acd9 100644
--- a/graphql/e2e/schema/generatedSchema.graphql
+++ b/graphql/e2e/schema/generatedSchema.graphql
@@ -79,6 +79,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/resolve/custom_mutation_test.yaml b/graphql/resolve/custom_mutation_test.yaml
index ea6d8a05750..0a6523651cb 100644
--- a/graphql/resolve/custom_mutation_test.yaml
+++ b/graphql/resolve/custom_mutation_test.yaml
@@ -43,7 +43,7 @@
         { "name": "Mov2" }
       ]
     }
-  headers: { "X-App-Token": ["val"], "Auth0-Token": ["tok"] }
+  headers: { "X-App-Token": ["val"], "Auth0-Token": ["tok"], "Content-type": ["application/json"] }
   resolvedresponse: |
     {
       "createMyFavouriteMovies": [
@@ -104,6 +104,7 @@
         "director": [ { "name": "Dir1" } ]
       }
     }
+  headers: { "Content-type": ["application/json"] }
   resolvedresponse: |
     {
       "updateMyFavouriteMovie": {
@@ -147,6 +148,7 @@
     }
   url: http://myapi.com/favMovies/0x01
   method: DELETE
+  headers: { "Content-type": ["application/json"] }
   resolvedresponse: |
     {
       "deleteMyFavouriteMovie": {
diff --git a/graphql/resolve/custom_query_test.yaml b/graphql/resolve/custom_query_test.yaml
index a8875500418..d83f68135c9 100644
--- a/graphql/resolve/custom_query_test.yaml
+++ b/graphql/resolve/custom_query_test.yaml
@@ -30,6 +30,7 @@
     ]
   url: http://myapi.com/favMovies/0x1?name=Michael&num=
   method: GET
+  headers: { "Content-type": ["application/json"] }
   resolvedresponse: |
     {
       "myFavoriteMovies": [
@@ -84,7 +85,7 @@
   url: http://myapi.com/favMovies/0x9?name=Michael&num=10
   method: POST
   body: '{ "id": "0x9", "name": "Michael", "director": { "number": 10 }}'
-  headers: { "X-App-Token": ["val"], "Auth0-Token": ["tok"] }
+  headers: { "X-App-Token": ["val"], "Auth0-Token": ["tok"], "Content-type": ["application/json"] }
   resolvedresponse: |
     {
       "myFavoriteMoviesPart2": [
diff --git a/graphql/resolve/resolver.go b/graphql/resolve/resolver.go
index 7fdbcb69aea..091337792b7 100644
--- a/graphql/resolve/resolver.go
+++ b/graphql/resolve/resolver.go
@@ -29,6 +29,8 @@ import (
 	"sync"
 	"time"
 
+	"github.com/dgraph-io/dgraph/graphql/authorization"
+
 	"github.com/dgraph-io/dgraph/edgraph"
 	"github.com/dgraph-io/dgraph/graphql/dgraph"
 	"github.com/dgraph-io/dgraph/types"
@@ -749,7 +751,7 @@ func completeDgraphResult(
 	// it should be using f.DgraphAlias() to get values from valToComplete.
 	// It works ATM because there hasn't been a scenario where there are two fields with same
 	// name in implementing types of an interface with @custom on some field in those types.
-	err = resolveCustomFields(field.SelectionSet(), valToComplete[field.DgraphAlias()])
+	err = resolveCustomFields(ctx, field.SelectionSet(), valToComplete[field.DgraphAlias()])
 	if err != nil {
 		errs = append(errs, schema.AsGQLErrors(err)...)
 	}
@@ -810,7 +812,8 @@ type graphqlResp struct {
 	Errors x.GqlErrorList         `json:"errors,omitempty"`
 }
 
-func resolveCustomField(f schema.Field, vals []interface{}, mu *sync.RWMutex, errCh chan error) {
+func resolveCustomField(ctx context.Context, f schema.Field, vals []interface{}, mu *sync.RWMutex,
+	errCh chan error) {
 	defer api.PanicHandler(func(err error) {
 		errCh <- internalServerError(err, f)
 	})
@@ -876,6 +879,8 @@ func resolveCustomField(f schema.Field, vals []interface{}, mu *sync.RWMutex, er
 			body["query"] = fconf.RemoteGqlQuery
 			body["variables"] = map[string]interface{}{fconf.GraphqlBatchModeArgument: requestInput}
 			requestInput = body
+		} else if f.HasLambdaDirective() {
+			requestInput = getBodyForLambda(ctx, f, requestInput, nil)
 		}
 
 		b, err := json.Marshal(requestInput)
@@ -1040,7 +1045,7 @@ func resolveCustomField(f schema.Field, vals []interface{}, mu *sync.RWMutex, er
 // }
 // In the example above, resolveNestedFields would be called on classes field and vals would be the
 // list of all users.
-func resolveNestedFields(f schema.Field, vals []interface{}, mu *sync.RWMutex,
+func resolveNestedFields(ctx context.Context, f schema.Field, vals []interface{}, mu *sync.RWMutex,
 	errCh chan error) {
 	defer api.PanicHandler(func(err error) {
 		errCh <- internalServerError(err, f)
@@ -1119,7 +1124,7 @@ func resolveNestedFields(f schema.Field, vals []interface{}, mu *sync.RWMutex,
 	}
 	mu.RUnlock()
 
-	if err := resolveCustomFields(f.SelectionSet(), input); err != nil {
+	if err := resolveCustomFields(ctx, f.SelectionSet(), input); err != nil {
 		errCh <- err
 		return
 	}
@@ -1183,7 +1188,7 @@ func resolveNestedFields(f schema.Field, vals []interface{}, mu *sync.RWMutex,
 // work.
 // TODO - We can be smarter about this and know before processing the query if we should be making
 // this recursive call upfront.
-func resolveCustomFields(fields []schema.Field, data interface{}) error {
+func resolveCustomFields(ctx context.Context, fields []schema.Field, data interface{}) error {
 	if data == nil {
 		return nil
 	}
@@ -1214,9 +1219,9 @@ func resolveCustomFields(fields []schema.Field, data interface{}) error {
 		numRoutines++
 		hasCustomDirective, _ := f.HasCustomDirective()
 		if !hasCustomDirective {
-			go resolveNestedFields(f, vals, mu, errCh)
+			go resolveNestedFields(ctx, f, vals, mu, errCh)
 		} else {
-			go resolveCustomField(f, vals, mu, errCh)
+			go resolveCustomField(ctx, f, vals, mu, errCh)
 		}
 	}
 
@@ -1789,6 +1794,23 @@ func makeRequest(client *http.Client, method, url, body string,
 	return b, err
 }
 
+func getBodyForLambda(ctx context.Context, field schema.Field, parents,
+	args interface{}) map[string]interface{} {
+	body := make(map[string]interface{})
+	body["resolver"] = field.GetObjectName() + "." + field.Name()
+	body["authHeader"] = map[string]interface{}{
+		"key":   authorization.GetHeader(),
+		"value": authorization.GetJwtToken(ctx),
+	}
+	if parents != nil {
+		body["parents"] = parents
+	}
+	if args != nil {
+		body["args"] = args
+	}
+	return body
+}
+
 func (hr *httpResolver) rewriteAndExecute(ctx context.Context, field schema.Field) *Resolved {
 	emptyResult := func(err error) *Resolved {
 		return &Resolved{
@@ -1805,7 +1827,11 @@ func (hr *httpResolver) rewriteAndExecute(ctx context.Context, field schema.Fiel
 
 	var body string
 	if hrc.Template != nil {
-		b, err := json.Marshal(*hrc.Template)
+		jsonTemplate := *hrc.Template
+		if field.HasLambdaDirective() {
+			jsonTemplate = getBodyForLambda(ctx, field, nil, *hrc.Template)
+		}
+		b, err := json.Marshal(jsonTemplate)
 		if err != nil {
 			return emptyResult(jsonMarshalError(err, field, *hrc.Template))
 		}
diff --git a/graphql/schema/dgraph_schemagen_test.yml b/graphql/schema/dgraph_schemagen_test.yml
index 0f4ff113f1c..273524c90b2 100644
--- a/graphql/schema/dgraph_schemagen_test.yml
+++ b/graphql/schema/dgraph_schemagen_test.yml
@@ -594,4 +594,21 @@ schemas:
           url: "http://mock:8888/users",
           method: "POST"
         })
-      }
\ No newline at end of file
+      }
+  -
+    name: "custom field shouldn't be part of dgraph schema"
+    input: |
+      type User {
+        id: ID!
+        name: String!
+        bio: String! @lambda
+        friends: [User] @custom(http: {
+          url: "http://mock:8888/users",
+          method: "GET"
+        })
+      }
+    output: |
+      type User {
+        User.name
+      }
+      User.name: string .
diff --git a/graphql/schema/gqlschema.go b/graphql/schema/gqlschema.go
index c001101f544..5da1f1d52cc 100644
--- a/graphql/schema/gqlschema.go
+++ b/graphql/schema/gqlschema.go
@@ -44,12 +44,18 @@ const (
 	remoteDirective       = "remote" // types with this directive are not stored in Dgraph.
 	cascadeDirective      = "cascade"
 	SubscriptionDirective = "withSubscription"
+	lambdaDirective       = "lambda"
 
 	// custom directive args and fields
-	dqlArg = "dql"
-	mode   = "mode"
-	BATCH  = "BATCH"
-	SINGLE = "SINGLE"
+	dqlArg      = "dql"
+	httpArg     = "http"
+	httpUrl     = "url"
+	httpMethod  = "method"
+	httpBody    = "body"
+	httpGraphql = "graphql"
+	mode        = "mode"
+	BATCH       = "BATCH"
+	SINGLE      = "SINGLE"
 
 	deprecatedDirective = "deprecated"
 	NumUid              = "numUids"
@@ -129,6 +135,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
@@ -318,7 +325,8 @@ var directiveValidators = map[string]directiveValidator{
 	deprecatedDirective:   ValidatorNoOp,
 	SubscriptionDirective: ValidatorNoOp,
 	// Just go get it printed into generated schema
-	authDirective: ValidatorNoOp,
+	authDirective:   ValidatorNoOp,
+	lambdaDirective: lambdaDirectiveValidation,
 }
 
 var schemaDocValidations []func(schema *ast.SchemaDocument) gqlerror.List
@@ -740,10 +748,9 @@ func addPatchType(schema *ast.Schema, defn *ast.Definition) {
 // }
 func addFieldFilters(schema *ast.Schema, defn *ast.Definition) {
 	for _, fld := range defn.Fields {
-		custom := fld.Directives.ForName(customDirective)
-		// Filtering and ordering for fields with @custom directive is handled by the remote
+		// Filtering and ordering for fields with @custom/@lambda directive is handled by the remote
 		// endpoint.
-		if custom != nil {
+		if hasCustomOrLambda(fld) {
 			continue
 		}
 
@@ -915,12 +922,13 @@ func hasFilterable(defn *ast.Definition) bool {
 }
 
 func hasOrderables(defn *ast.Definition) bool {
-	return fieldAny(defn.Fields,
-		func(fld *ast.FieldDefinition) bool {
-			// lists can't be ordered and NamedType will be empty for lists,
-			// so it will return false for list fields
-			return orderable[fld.Type.NamedType]
-		})
+	return fieldAny(defn.Fields, isOrderable)
+}
+
+func isOrderable(fld *ast.FieldDefinition) bool {
+	// lists can't be ordered and NamedType will be empty for lists,
+	// so it will return false for list fields
+	return orderable[fld.Type.NamedType] && !hasCustomOrLambda(fld)
 }
 
 func hasID(defn *ast.Definition) bool {
@@ -1041,7 +1049,7 @@ func addTypeOrderable(schema *ast.Schema, defn *ast.Definition) {
 	}
 
 	for _, fld := range defn.Fields {
-		if fld.Type.NamedType != "" && orderable[fld.Type.NamedType] {
+		if isOrderable(fld) {
 			order.EnumValues = append(order.EnumValues,
 				&ast.EnumValueDefinition{Name: fld.Name})
 		}
@@ -1352,9 +1360,9 @@ func getNonIDFields(schema *ast.Schema, defn *ast.Definition) ast.FieldList {
 			continue
 		}
 
-		custom := fld.Directives.ForName(customDirective)
-		// Fields with @custom directive should not be part of mutation input, hence we skip them.
-		if custom != nil {
+		// Fields with @custom/@lambda directive should not be part of mutation input,
+		// hence we skip them.
+		if hasCustomOrLambda(fld) {
 			continue
 		}
 
@@ -1393,9 +1401,9 @@ func getFieldsWithoutIDType(schema *ast.Schema, defn *ast.Definition) ast.FieldL
 			continue
 		}
 
-		custom := fld.Directives.ForName(customDirective)
-		// Fields with @custom directive should not be part of mutation input, hence we skip them.
-		if custom != nil {
+		// Fields with @custom/@lambda directive should not be part of mutation input,
+		// hence we skip them.
+		if hasCustomOrLambda(fld) {
 			continue
 		}
 
diff --git a/graphql/schema/gqlschema_test.yml b/graphql/schema/gqlschema_test.yml
index f7d08401c18..5f841185677 100644
--- a/graphql/schema/gqlschema_test.yml
+++ b/graphql/schema/gqlschema_test.yml
@@ -9,7 +9,7 @@ invalid_schemas:
       }
     errlist: [
       {"message":"Fields id1, id2 and id3 are listed as IDs for type P, but a type can have only one ID field. Pick a single field as the ID for type P.", "locations":[{"line":2, "column":3}, {"line":3, "column":3}, {"line":4, "column":3}]},
-      {"message":"Type P; is invalid, a type must have atleast one field that is not of ID! type and doesn't have @custom directive.", "locations":[{"line":1, "column":6}]}
+      {"message":"Type P; is invalid, a type must have atleast one field that is not of ID! type and doesn't have @custom/@lambda directive.", "locations":[{"line":1, "column":6}]}
     ]
 
   -
@@ -33,11 +33,11 @@ invalid_schemas:
       }
     errlist: [
       {"message":"GraphQL Query and Mutation types are only allowed to have fields
-      with @custom directive. Other fields are built automatically for you. Found Query getAuthor
-      without @custom.", "locations":[{"line":1, "column":6}]},
+      with @custom/@lambda directive. Other fields are built automatically for you. Found Query getAuthor
+      without @custom/@lambda.", "locations":[{"line":1, "column":6}]},
       {"message":"GraphQL Query and Mutation types are only allowed to have fields with
-      @custom directive. Other fields are built automatically for you. Found Mutation getAuthor
-      without @custom.", "locations":[{"line":4, "column":6}]},
+      @custom/@lambda directive. Other fields are built automatically for you. Found Mutation getAuthor
+      without @custom/@lambda.", "locations":[{"line":4, "column":6}]},
     ]
 
   -
@@ -1574,7 +1574,7 @@ invalid_schemas:
       ]
     },
     {
-      "message": "Type Author; Field name; @custom directive, body template can't use another field with @custom directive, found field `name` with @custom.",
+      "message": "Type Author; Field name; @custom directive, body template can't use another field with @custom/@lambda directive, found field `name` with @custom/@lambda.",
       "locations": [
       {
         "line": 6,
@@ -1656,7 +1656,7 @@ invalid_schemas:
         })
       }
     errlist: [
-    {"message": "Type Author; Field yo; @custom directive, body template can't use another field with @custom directive, found field `foo` with @custom.",
+    {"message": "Type Author; Field yo; @custom directive, body template can't use another field with @custom/@lambda directive, found field `foo` with @custom/@lambda.",
      "locations":[{"line":12, "column":12}]},
     ]
 
@@ -1701,7 +1701,7 @@ invalid_schemas:
       ]
     },
     {
-      "message": "Type Author; Field name; @custom directive, graphql can't use another field with @custom directive, found field `name` with @custom.",
+      "message": "Type Author; Field name; @custom directive, graphql can't use another field with @custom/@lambda directive, found field `name` with @custom/@lambda.",
       "locations": [
       {
         "line": 6,
@@ -1807,7 +1807,7 @@ invalid_schemas:
       }
     errlist: [
     {
-      "message": "Type Author; Field yo; @custom directive, graphql can't use another field with @custom directive, found field `foo` with @custom.",
+      "message": "Type Author; Field yo; @custom directive, graphql can't use another field with @custom/@lambda directive, found field `foo` with @custom/@lambda.",
       "locations": [
       {
         "line": 12,
@@ -2297,7 +2297,7 @@ invalid_schemas:
       }
 
     errlist: [
-      {"message": "Type Author; is invalid, a type must have atleast one field that is not of ID! type and doesn't have @custom directive.",
+      {"message": "Type Author; is invalid, a type must have atleast one field that is not of ID! type and doesn't have @custom/@lambda directive.",
         "locations":[{"line":1, "column":6}]},
       ]
 
@@ -2314,7 +2314,7 @@ invalid_schemas:
         })
       }
     errlist: [
-      {"message": "Type Author; is invalid, a type must have atleast one field that is not of ID! type and doesn't have @custom directive.",
+      {"message": "Type Author; is invalid, a type must have atleast one field that is not of ID! type and doesn't have @custom/@lambda directive.",
         "locations":[{"line":1, "column":6}]},
       ]
 
@@ -2368,8 +2368,8 @@ invalid_schemas:
                 })
       }
     errlist: [
-    {"message": "Type School; field name; can't have @custom directive as a @remote
-     type can't have fields with @custom directive.", "locations": [{"line":9, "column":3}]}
+    {"message": "Type School; field name; can't have @custom/@lambda directive as a @remote
+     type can't have fields with @custom/@lambda directive.", "locations": [{"line":9, "column":3}]}
     ]
 
   -
@@ -2389,7 +2389,7 @@ invalid_schemas:
       }
     errlist: [
     {"message": "Type Author; field neighbour; is of a type that has @remote directive. Those
-    would need to be resolved by a @custom directive.",
+    would need to be resolved by a @custom/@lambda directive.",
      "locations": [{"line":9, "column":3}]}
     ]
 
diff --git a/graphql/schema/rules.go b/graphql/schema/rules.go
index 58f68c69435..524be72d407 100644
--- a/graphql/schema/rules.go
+++ b/graphql/schema/rules.go
@@ -425,13 +425,12 @@ func nameCheck(schema *ast.Schema, defn *ast.Definition) gqlerror.List {
 
 		if isQueryOrMutationType(defn) {
 			for _, fld := range defn.Fields {
-				// If we find any query or mutation field defined without a @custom directive, that
-				// is an error for us.
-				custom := fld.Directives.ForName(customDirective)
-				if custom == nil {
+				// If we find any query or mutation field defined without a @custom/@lambda
+				// directive, that is an error for us.
+				if !hasCustomOrLambda(fld) {
 					errMesg = "GraphQL Query and Mutation types are only allowed to have fields " +
-						"with @custom directive. Other fields are built automatically for you. " +
-						"Found " + defn.Name + " " + fld.Name + " without @custom."
+						"with @custom/@lambda directive. Other fields are built automatically for" +
+						" you. Found " + defn.Name + " " + fld.Name + " without @custom/@lambda."
 					break
 				}
 			}
@@ -581,8 +580,7 @@ func nonIdFieldsCheck(schema *ast.Schema, typ *ast.Definition) gqlerror.List {
 
 	hasNonIdField := false
 	for _, field := range typ.Fields {
-		custom := field.Directives.ForName(customDirective)
-		if isIDField(typ, field) || custom != nil {
+		if isIDField(typ, field) || hasCustomOrLambda(field) {
 			continue
 		}
 		hasNonIdField = true
@@ -591,7 +589,8 @@ func nonIdFieldsCheck(schema *ast.Schema, typ *ast.Definition) gqlerror.List {
 
 	if !hasNonIdField {
 		return []*gqlerror.Error{gqlerror.ErrorPosf(typ.Position, "Type %s; is invalid, a type must have atleast "+
-			"one field that is not of ID! type and doesn't have @custom directive.", typ.Name)}
+			"one field that is not of ID! type and doesn't have @custom/@lambda directive.",
+			typ.Name)}
 	}
 	return nil
 }
@@ -605,8 +604,7 @@ func remoteTypeValidation(schema *ast.Schema, typ *ast.Definition) gqlerror.List
 		for _, field := range typ.Fields {
 			// If the field is being resolved through a custom directive, then we don't care if
 			// the type for the field is a remote or a non-remote type.
-			custom := field.Directives.ForName(customDirective)
-			if custom != nil {
+			if hasCustomOrLambda(field) {
 				continue
 			}
 			t := field.Type.Name()
@@ -615,7 +613,7 @@ func remoteTypeValidation(schema *ast.Schema, typ *ast.Definition) gqlerror.List
 			if remoteDir != nil {
 				return []*gqlerror.Error{gqlerror.ErrorPosf(field.Position, "Type %s; "+
 					"field %s; is of a type that has @remote directive. Those would need to be "+
-					"resolved by a @custom directive.", typ.Name, field.Name)}
+					"resolved by a @custom/@lambda directive.", typ.Name, field.Name)}
 			}
 		}
 
@@ -633,11 +631,10 @@ func remoteTypeValidation(schema *ast.Schema, typ *ast.Definition) gqlerror.List
 
 	// This means that the type was a remote type.
 	for _, field := range typ.Fields {
-		custom := field.Directives.ForName(customDirective)
-		if custom != nil {
+		if hasCustomOrLambda(field) {
 			return []*gqlerror.Error{gqlerror.ErrorPosf(field.Position, "Type %s; "+
-				"field %s; can't have @custom directive as a @remote type can't have fields with"+
-				" @custom directive.", typ.Name, field.Name)}
+				"field %s; can't have @custom/@lambda directive as a @remote type can't have"+
+				" fields with @custom/@lambda directive.", typ.Name, field.Name)}
 		}
 
 	}
@@ -1181,6 +1178,28 @@ func passwordValidation(sch *ast.Schema,
 	return passwordDirectiveValidation(sch, typ)
 }
 
+func lambdaDirectiveValidation(sch *ast.Schema,
+	typ *ast.Definition,
+	field *ast.FieldDefinition,
+	dir *ast.Directive,
+	secrets map[string]x.SensitiveByteSlice) gqlerror.List {
+	// if the lambda url wasn't specified during alpha startup,
+	// just return that error. Don't confuse the user with errors from @custom yet.
+	if x.Config.GraphqlLambdaUrl == "" {
+		return []*gqlerror.Error{gqlerror.ErrorPosf(dir.Position,
+			"Type %s; Field %s: has the @lambda directive, but the "+
+				"`--graphql_lambda_url` flag wasn't specified during alpha startup.",
+			typ.Name, field.Name)}
+	}
+	// reuse @custom directive validation
+	errs := customDirectiveValidation(sch, typ, field, buildCustomDirectiveForLambda(typ, field,
+		dir, func(f *ast.FieldDefinition) bool { return false }), secrets)
+	for _, err := range errs {
+		err.Message = "While building @custom for @lambda: " + err.Message
+	}
+	return errs
+}
+
 func customDirectiveValidation(sch *ast.Schema,
 	typ *ast.Definition,
 	field *ast.FieldDefinition,
@@ -1228,7 +1247,7 @@ func customDirectiveValidation(sch *ast.Schema,
 			typ.Name, field.Name, l))
 	}
 
-	httpArg := dir.Arguments.ForName("http")
+	httpArg := dir.Arguments.ForName(httpArg)
 	dqlArg := dir.Arguments.ForName(dqlArg)
 
 	if httpArg == nil && dqlArg == nil {
@@ -1301,7 +1320,7 @@ func customDirectiveValidation(sch *ast.Schema,
 	// Start validating children of http argument
 
 	// 4. Validating url
-	httpUrl := httpArg.Value.Children.ForName("url")
+	httpUrl := httpArg.Value.Children.ForName(httpUrl)
 	if httpUrl == nil {
 		errs = append(errs, gqlerror.ErrorPosf(
 			dir.Position,
@@ -1377,7 +1396,7 @@ func customDirectiveValidation(sch *ast.Schema,
 	}
 
 	// 5. Validating method
-	method := httpArg.Value.Children.ForName("method")
+	method := httpArg.Value.Children.ForName(httpMethod)
 	if method == nil {
 		errs = append(errs, gqlerror.ErrorPosf(
 			dir.Position,
@@ -1422,8 +1441,8 @@ func customDirectiveValidation(sch *ast.Schema,
 	}
 
 	// 7. Validating graphql combination with url params, method and body
-	body := httpArg.Value.Children.ForName("body")
-	graphql := httpArg.Value.Children.ForName("graphql")
+	body := httpArg.Value.Children.ForName(httpBody)
+	graphql := httpArg.Value.Children.ForName(httpGraphql)
 	if graphql != nil {
 		if urlHasParams {
 			errs = append(errs, gqlerror.ErrorPosf(dir.Position,
@@ -1689,11 +1708,11 @@ func customDirectiveValidation(sch *ast.Schema,
 						fname, typName))
 				}
 
-				if fd.Directives.ForName(customDirective) != nil {
+				if hasCustomOrLambda(fd) {
 					errs = append(errs, gqlerror.ErrorPosf(errPos,
 						"Type %s; Field %s; @custom directive, %s can't use another field with "+
-							"@custom directive, found field `%s` with @custom.", typ.Name,
-						field.Name, errIn, fname))
+							"@custom/@lambda directive, found field `%s` with @custom/@lambda.",
+						typ.Name, field.Name, errIn, fname))
 				}
 
 				if fname == idField || fname == xidField {
diff --git a/graphql/schema/schemagen.go b/graphql/schema/schemagen.go
index dc42c2fb86a..8e011dc32b8 100644
--- a/graphql/schema/schemagen.go
+++ b/graphql/schema/schemagen.go
@@ -395,7 +395,7 @@ func genDgSchema(gqlSch *ast.Schema, definitions []string) string {
 			pwdField := getPasswordField(def)
 
 			for _, f := range def.Fields {
-				if f.Type.Name() == "ID" {
+				if f.Type.Name() == "ID" || hasCustomOrLambda(f) {
 					continue
 				}
 
diff --git a/graphql/schema/schemagen_test.go b/graphql/schema/schemagen_test.go
index f69b0b32dc4..35173540629 100644
--- a/graphql/schema/schemagen_test.go
+++ b/graphql/schema/schemagen_test.go
@@ -18,6 +18,7 @@ package schema
 
 import (
 	"io/ioutil"
+	"os"
 	"strings"
 	"testing"
 
@@ -309,3 +310,10 @@ func TestOnlyCorrectSearchArgsWork(t *testing.T) {
 		})
 	}
 }
+
+func TestMain(m *testing.M) {
+	// set up the lambda url for unit tests
+	x.Config.GraphqlLambdaUrl = "http://localhost:8086/graphql-worker"
+	// now run the tests
+	os.Exit(m.Run())
+}
diff --git a/graphql/schema/testdata/schemagen/input/lambda-directive.graphql b/graphql/schema/testdata/schemagen/input/lambda-directive.graphql
new file mode 100644
index 00000000000..273f3ee54e9
--- /dev/null
+++ b/graphql/schema/testdata/schemagen/input/lambda-directive.graphql
@@ -0,0 +1,14 @@
+type User {
+	id: ID!
+	firstName: String!
+	lastName: String!
+	fullName: String @lambda
+}
+
+type Query {
+	queryUserNames(id: [ID!]!): [String] @lambda
+}
+
+type Mutation {
+	createUser(firstName: String!, lastName: String!): User @lambda
+}
\ No newline at end of file
diff --git a/graphql/schema/testdata/schemagen/output/authorization.graphql b/graphql/schema/testdata/schemagen/output/authorization.graphql
index cfa0d319bd9..44e4790a031 100644
--- a/graphql/schema/testdata/schemagen/output/authorization.graphql
+++ b/graphql/schema/testdata/schemagen/output/authorization.graphql
@@ -90,6 +90,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/comments-and-descriptions.graphql b/graphql/schema/testdata/schemagen/output/comments-and-descriptions.graphql
index de76461219f..b84a1409edd 100755
--- a/graphql/schema/testdata/schemagen/output/comments-and-descriptions.graphql
+++ b/graphql/schema/testdata/schemagen/output/comments-and-descriptions.graphql
@@ -95,6 +95,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/custom-mutation.graphql b/graphql/schema/testdata/schemagen/output/custom-mutation.graphql
index 4cb66a6d07c..ed6e901dbde 100644
--- a/graphql/schema/testdata/schemagen/output/custom-mutation.graphql
+++ b/graphql/schema/testdata/schemagen/output/custom-mutation.graphql
@@ -83,6 +83,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/custom-nested-types.graphql b/graphql/schema/testdata/schemagen/output/custom-nested-types.graphql
index baca392f26c..c2966a5862f 100755
--- a/graphql/schema/testdata/schemagen/output/custom-nested-types.graphql
+++ b/graphql/schema/testdata/schemagen/output/custom-nested-types.graphql
@@ -100,6 +100,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/custom-query-mixed-types.graphql b/graphql/schema/testdata/schemagen/output/custom-query-mixed-types.graphql
index c62940c1f5b..2a1fc063a87 100644
--- a/graphql/schema/testdata/schemagen/output/custom-query-mixed-types.graphql
+++ b/graphql/schema/testdata/schemagen/output/custom-query-mixed-types.graphql
@@ -84,6 +84,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/custom-query-not-dgraph-type.graphql b/graphql/schema/testdata/schemagen/output/custom-query-not-dgraph-type.graphql
index f0c787c2e94..cf1052f02d0 100755
--- a/graphql/schema/testdata/schemagen/output/custom-query-not-dgraph-type.graphql
+++ b/graphql/schema/testdata/schemagen/output/custom-query-not-dgraph-type.graphql
@@ -83,6 +83,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/custom-query-with-dgraph-type.graphql b/graphql/schema/testdata/schemagen/output/custom-query-with-dgraph-type.graphql
index 188ee9a56b6..94ba91e7d72 100755
--- a/graphql/schema/testdata/schemagen/output/custom-query-with-dgraph-type.graphql
+++ b/graphql/schema/testdata/schemagen/output/custom-query-with-dgraph-type.graphql
@@ -79,6 +79,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/deprecated.graphql b/graphql/schema/testdata/schemagen/output/deprecated.graphql
index d05029e2691..6b041d23f8c 100755
--- a/graphql/schema/testdata/schemagen/output/deprecated.graphql
+++ b/graphql/schema/testdata/schemagen/output/deprecated.graphql
@@ -79,6 +79,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/dgraph-reverse-directive-on-concrete-type-with-interfaces.graphql b/graphql/schema/testdata/schemagen/output/dgraph-reverse-directive-on-concrete-type-with-interfaces.graphql
index cc51bc4e836..3d3086362b4 100755
--- a/graphql/schema/testdata/schemagen/output/dgraph-reverse-directive-on-concrete-type-with-interfaces.graphql
+++ b/graphql/schema/testdata/schemagen/output/dgraph-reverse-directive-on-concrete-type-with-interfaces.graphql
@@ -93,6 +93,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/dgraph-reverse-directive-with-interfaces.graphql b/graphql/schema/testdata/schemagen/output/dgraph-reverse-directive-with-interfaces.graphql
index 88d0edf56bf..9469d7b6161 100755
--- a/graphql/schema/testdata/schemagen/output/dgraph-reverse-directive-with-interfaces.graphql
+++ b/graphql/schema/testdata/schemagen/output/dgraph-reverse-directive-with-interfaces.graphql
@@ -93,6 +93,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/field-with-id-directive.graphql b/graphql/schema/testdata/schemagen/output/field-with-id-directive.graphql
index bf7e45e6acd..0412f042de9 100755
--- a/graphql/schema/testdata/schemagen/output/field-with-id-directive.graphql
+++ b/graphql/schema/testdata/schemagen/output/field-with-id-directive.graphql
@@ -92,6 +92,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/field-with-reverse-predicate-in-dgraph-directive.graphql b/graphql/schema/testdata/schemagen/output/field-with-reverse-predicate-in-dgraph-directive.graphql
index 3def6cff8e7..130f5afc9ad 100755
--- a/graphql/schema/testdata/schemagen/output/field-with-reverse-predicate-in-dgraph-directive.graphql
+++ b/graphql/schema/testdata/schemagen/output/field-with-reverse-predicate-in-dgraph-directive.graphql
@@ -86,6 +86,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/filter-cleanSchema-directLink.graphql b/graphql/schema/testdata/schemagen/output/filter-cleanSchema-directLink.graphql
index 7850a1369cb..38eb882a021 100644
--- a/graphql/schema/testdata/schemagen/output/filter-cleanSchema-directLink.graphql
+++ b/graphql/schema/testdata/schemagen/output/filter-cleanSchema-directLink.graphql
@@ -89,6 +89,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/hasInverse-with-interface-having-directive.graphql b/graphql/schema/testdata/schemagen/output/hasInverse-with-interface-having-directive.graphql
index 50f0faca1a7..47ab5c5dc34 100755
--- a/graphql/schema/testdata/schemagen/output/hasInverse-with-interface-having-directive.graphql
+++ b/graphql/schema/testdata/schemagen/output/hasInverse-with-interface-having-directive.graphql
@@ -103,6 +103,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/hasInverse-with-interface.graphql b/graphql/schema/testdata/schemagen/output/hasInverse-with-interface.graphql
index 7b09a60441c..0d297312fb5 100755
--- a/graphql/schema/testdata/schemagen/output/hasInverse-with-interface.graphql
+++ b/graphql/schema/testdata/schemagen/output/hasInverse-with-interface.graphql
@@ -104,6 +104,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/hasInverse-with-type-having-directive.graphql b/graphql/schema/testdata/schemagen/output/hasInverse-with-type-having-directive.graphql
index 50f0faca1a7..47ab5c5dc34 100755
--- a/graphql/schema/testdata/schemagen/output/hasInverse-with-type-having-directive.graphql
+++ b/graphql/schema/testdata/schemagen/output/hasInverse-with-type-having-directive.graphql
@@ -103,6 +103,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/hasInverse.graphql b/graphql/schema/testdata/schemagen/output/hasInverse.graphql
index 4f99a739079..fade3710070 100755
--- a/graphql/schema/testdata/schemagen/output/hasInverse.graphql
+++ b/graphql/schema/testdata/schemagen/output/hasInverse.graphql
@@ -84,6 +84,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/hasInverse_withSubscription.graphql b/graphql/schema/testdata/schemagen/output/hasInverse_withSubscription.graphql
index fd4661da0e7..3bfc317ea9a 100755
--- a/graphql/schema/testdata/schemagen/output/hasInverse_withSubscription.graphql
+++ b/graphql/schema/testdata/schemagen/output/hasInverse_withSubscription.graphql
@@ -84,6 +84,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/ignore-unsupported-directive.graphql b/graphql/schema/testdata/schemagen/output/ignore-unsupported-directive.graphql
index 16a4b071f94..3ff46e78d1e 100755
--- a/graphql/schema/testdata/schemagen/output/ignore-unsupported-directive.graphql
+++ b/graphql/schema/testdata/schemagen/output/ignore-unsupported-directive.graphql
@@ -86,6 +86,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/interface-with-dgraph-pred.graphql b/graphql/schema/testdata/schemagen/output/interface-with-dgraph-pred.graphql
index 80e566e6462..854d28418d6 100644
--- a/graphql/schema/testdata/schemagen/output/interface-with-dgraph-pred.graphql
+++ b/graphql/schema/testdata/schemagen/output/interface-with-dgraph-pred.graphql
@@ -93,6 +93,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/interface-with-id-directive.graphql b/graphql/schema/testdata/schemagen/output/interface-with-id-directive.graphql
index 46da5584d0a..b95d614cbf6 100755
--- a/graphql/schema/testdata/schemagen/output/interface-with-id-directive.graphql
+++ b/graphql/schema/testdata/schemagen/output/interface-with-id-directive.graphql
@@ -88,6 +88,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/interface-with-no-ids.graphql b/graphql/schema/testdata/schemagen/output/interface-with-no-ids.graphql
index 44793b34847..04c8b76b0cc 100755
--- a/graphql/schema/testdata/schemagen/output/interface-with-no-ids.graphql
+++ b/graphql/schema/testdata/schemagen/output/interface-with-no-ids.graphql
@@ -88,6 +88,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/interfaces-with-types-and-password.graphql b/graphql/schema/testdata/schemagen/output/interfaces-with-types-and-password.graphql
index 2df8fdc2418..f1728af4d90 100755
--- a/graphql/schema/testdata/schemagen/output/interfaces-with-types-and-password.graphql
+++ b/graphql/schema/testdata/schemagen/output/interfaces-with-types-and-password.graphql
@@ -110,6 +110,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/interfaces-with-types.graphql b/graphql/schema/testdata/schemagen/output/interfaces-with-types.graphql
index 9a28357195a..38539ebd863 100755
--- a/graphql/schema/testdata/schemagen/output/interfaces-with-types.graphql
+++ b/graphql/schema/testdata/schemagen/output/interfaces-with-types.graphql
@@ -110,6 +110,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/lambda-directive.graphql b/graphql/schema/testdata/schemagen/output/lambda-directive.graphql
new file mode 100644
index 00000000000..2232f907823
--- /dev/null
+++ b/graphql/schema/testdata/schemagen/output/lambda-directive.graphql
@@ -0,0 +1,245 @@
+#######################
+# Input Schema
+#######################
+
+type User {
+	id: ID!
+	firstName: String!
+	lastName: String!
+	fullName: String @lambda
+}
+
+#######################
+# Extended Definitions
+#######################
+
+"""
+The Int64 scalar type represents a signed 64‐bit numeric non‐fractional value.
+Int64 can represent values in range [-(2^63),(2^63 - 1)].
+"""
+scalar Int64
+
+"""
+The DateTime scalar type represents date and time as a string in RFC3339 format.
+For example: "1985-04-12T23:20:50.52Z" represents 20 minutes and 50.52 seconds after the 23rd hour of April 12th, 1985 in UTC.
+"""
+scalar DateTime
+
+enum DgraphIndex {
+	int
+	int64
+	float
+	bool
+	hash
+	exact
+	term
+	fulltext
+	trigram
+	regexp
+	year
+	month
+	day
+	hour
+}
+
+input AuthRule {
+	and: [AuthRule]
+	or: [AuthRule]
+	not: AuthRule
+	rule: String
+}
+
+enum HTTPMethod {
+	GET
+	POST
+	PUT
+	PATCH
+	DELETE
+}
+
+enum Mode {
+	BATCH
+	SINGLE
+}
+
+input CustomHTTP {
+	url: String!
+	method: HTTPMethod!
+	body: String
+	graphql: String
+	mode: Mode
+	forwardHeaders: [String!]
+	secretHeaders: [String!]
+	introspectionHeaders: [String!]
+	skipIntrospection: Boolean
+}
+
+directive @hasInverse(field: String!) on FIELD_DEFINITION
+directive @search(by: [DgraphIndex!]) on FIELD_DEFINITION
+directive @dgraph(type: String, pred: String) on OBJECT | INTERFACE | FIELD_DEFINITION
+directive @id on FIELD_DEFINITION
+directive @withSubscription on OBJECT | INTERFACE
+directive @secret(field: String!, pred: String) on OBJECT | INTERFACE
+directive @auth(
+	query: AuthRule,
+	add: AuthRule,
+	update: AuthRule,
+	delete:AuthRule) on OBJECT
+directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
+directive @remote on OBJECT | INTERFACE
+directive @cascade(fields: [String]) on FIELD
+directive @lambda on FIELD_DEFINITION
+
+input IntFilter {
+	eq: Int
+	le: Int
+	lt: Int
+	ge: Int
+	gt: Int
+}
+
+input Int64Filter {
+	eq: Int64
+	le: Int64
+	lt: Int64
+	ge: Int64
+	gt: Int64
+}
+
+input FloatFilter {
+	eq: Float
+	le: Float
+	lt: Float
+	ge: Float
+	gt: Float
+}
+
+input DateTimeFilter {
+	eq: DateTime
+	le: DateTime
+	lt: DateTime
+	ge: DateTime
+	gt: DateTime
+}
+
+input StringTermFilter {
+	allofterms: String
+	anyofterms: String
+}
+
+input StringRegExpFilter {
+	regexp: String
+}
+
+input StringFullTextFilter {
+	alloftext: String
+	anyoftext: String
+}
+
+input StringExactFilter {
+	eq: String
+	le: String
+	lt: String
+	ge: String
+	gt: String
+}
+
+input StringHashFilter {
+	eq: String
+}
+
+#######################
+# Generated Types
+#######################
+
+type AddUserPayload {
+	user(filter: UserFilter, order: UserOrder, first: Int, offset: Int): [User]
+	numUids: Int
+}
+
+type DeleteUserPayload {
+	user(filter: UserFilter, order: UserOrder, first: Int, offset: Int): [User]
+	msg: String
+	numUids: Int
+}
+
+type UpdateUserPayload {
+	user(filter: UserFilter, order: UserOrder, first: Int, offset: Int): [User]
+	numUids: Int
+}
+
+#######################
+# Generated Enums
+#######################
+
+enum UserHasFilter {
+	firstName
+	lastName
+}
+
+enum UserOrderable {
+	firstName
+	lastName
+}
+
+#######################
+# Generated Inputs
+#######################
+
+input AddUserInput {
+	firstName: String!
+	lastName: String!
+}
+
+input UpdateUserInput {
+	filter: UserFilter!
+	set: UserPatch
+	remove: UserPatch
+}
+
+input UserFilter {
+	id: [ID!]
+	has: UserHasFilter
+	and: UserFilter
+	or: UserFilter
+	not: UserFilter
+}
+
+input UserOrder {
+	asc: UserOrderable
+	desc: UserOrderable
+	then: UserOrder
+}
+
+input UserPatch {
+	firstName: String
+	lastName: String
+}
+
+input UserRef {
+	id: ID
+	firstName: String
+	lastName: String
+}
+
+#######################
+# Generated Query
+#######################
+
+type Query {
+	queryUserNames(id: [ID!]!): [String] @lambda
+	getUser(id: ID!): User
+	queryUser(filter: UserFilter, order: UserOrder, first: Int, offset: Int): [User]
+}
+
+#######################
+# Generated Mutations
+#######################
+
+type Mutation {
+	createUser(firstName: String!, lastName: String!): User @lambda
+	addUser(input: [AddUserInput!]!): AddUserPayload
+	updateUser(input: UpdateUserInput!): UpdateUserPayload
+	deleteUser(filter: UserFilter!): DeleteUserPayload
+}
+
diff --git a/graphql/schema/testdata/schemagen/output/no-id-field-with-searchables.graphql b/graphql/schema/testdata/schemagen/output/no-id-field-with-searchables.graphql
index b8c18e78a43..3fe7133ba86 100755
--- a/graphql/schema/testdata/schemagen/output/no-id-field-with-searchables.graphql
+++ b/graphql/schema/testdata/schemagen/output/no-id-field-with-searchables.graphql
@@ -78,6 +78,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/no-id-field.graphql b/graphql/schema/testdata/schemagen/output/no-id-field.graphql
index 17e2fe9c24b..168d53f915c 100755
--- a/graphql/schema/testdata/schemagen/output/no-id-field.graphql
+++ b/graphql/schema/testdata/schemagen/output/no-id-field.graphql
@@ -90,6 +90,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/password-type.graphql b/graphql/schema/testdata/schemagen/output/password-type.graphql
index 162596735d2..03e864101fe 100755
--- a/graphql/schema/testdata/schemagen/output/password-type.graphql
+++ b/graphql/schema/testdata/schemagen/output/password-type.graphql
@@ -79,6 +79,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/searchables-references.graphql b/graphql/schema/testdata/schemagen/output/searchables-references.graphql
index a16f2f20a5b..29e8578d236 100755
--- a/graphql/schema/testdata/schemagen/output/searchables-references.graphql
+++ b/graphql/schema/testdata/schemagen/output/searchables-references.graphql
@@ -88,6 +88,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/searchables.graphql b/graphql/schema/testdata/schemagen/output/searchables.graphql
index 92eccb2f04f..566261f21f1 100755
--- a/graphql/schema/testdata/schemagen/output/searchables.graphql
+++ b/graphql/schema/testdata/schemagen/output/searchables.graphql
@@ -105,6 +105,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/single-type-with-enum.graphql b/graphql/schema/testdata/schemagen/output/single-type-with-enum.graphql
index 907d07108b7..82a8fc8fb93 100755
--- a/graphql/schema/testdata/schemagen/output/single-type-with-enum.graphql
+++ b/graphql/schema/testdata/schemagen/output/single-type-with-enum.graphql
@@ -87,6 +87,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/single-type.graphql b/graphql/schema/testdata/schemagen/output/single-type.graphql
index e62e29f57da..1306205fa06 100755
--- a/graphql/schema/testdata/schemagen/output/single-type.graphql
+++ b/graphql/schema/testdata/schemagen/output/single-type.graphql
@@ -81,6 +81,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/type-implements-multiple-interfaces.graphql b/graphql/schema/testdata/schemagen/output/type-implements-multiple-interfaces.graphql
index 9779f10fa44..351a9970e93 100755
--- a/graphql/schema/testdata/schemagen/output/type-implements-multiple-interfaces.graphql
+++ b/graphql/schema/testdata/schemagen/output/type-implements-multiple-interfaces.graphql
@@ -94,6 +94,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/type-reference.graphql b/graphql/schema/testdata/schemagen/output/type-reference.graphql
index 85272795aa2..0e94864fd7f 100755
--- a/graphql/schema/testdata/schemagen/output/type-reference.graphql
+++ b/graphql/schema/testdata/schemagen/output/type-reference.graphql
@@ -86,6 +86,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/type-with-arguments-on-field.graphql b/graphql/schema/testdata/schemagen/output/type-with-arguments-on-field.graphql
index ff2f410fd76..b3390d7be0f 100644
--- a/graphql/schema/testdata/schemagen/output/type-with-arguments-on-field.graphql
+++ b/graphql/schema/testdata/schemagen/output/type-with-arguments-on-field.graphql
@@ -87,6 +87,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/testdata/schemagen/output/type-with-custom-field-on-dgraph-type.graphql b/graphql/schema/testdata/schemagen/output/type-with-custom-field-on-dgraph-type.graphql
index a221255dac3..4aa5d49a1f5 100644
--- a/graphql/schema/testdata/schemagen/output/type-with-custom-field-on-dgraph-type.graphql
+++ b/graphql/schema/testdata/schemagen/output/type-with-custom-field-on-dgraph-type.graphql
@@ -86,6 +86,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
@@ -182,7 +183,6 @@ enum CarOrderable {
 }
 
 enum UserOrderable {
-	name
 	age
 }
 
diff --git a/graphql/schema/testdata/schemagen/output/type-with-custom-fields-on-remote-type.graphql b/graphql/schema/testdata/schemagen/output/type-with-custom-fields-on-remote-type.graphql
index 03953098fad..9871057598c 100644
--- a/graphql/schema/testdata/schemagen/output/type-with-custom-fields-on-remote-type.graphql
+++ b/graphql/schema/testdata/schemagen/output/type-with-custom-fields-on-remote-type.graphql
@@ -86,6 +86,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
@@ -162,7 +163,6 @@ type UpdateUserPayload {
 #######################
 
 enum UserOrderable {
-	name
 	age
 }
 
diff --git a/graphql/schema/testdata/schemagen/output/type-without-orderables.graphql b/graphql/schema/testdata/schemagen/output/type-without-orderables.graphql
index a9d26c25384..5b55fbba2a3 100644
--- a/graphql/schema/testdata/schemagen/output/type-without-orderables.graphql
+++ b/graphql/schema/testdata/schemagen/output/type-without-orderables.graphql
@@ -81,6 +81,7 @@ directive @auth(
 directive @custom(http: CustomHTTP, dql: String) on FIELD_DEFINITION
 directive @remote on OBJECT | INTERFACE
 directive @cascade on FIELD
+directive @lambda on FIELD_DEFINITION
 
 input IntFilter {
 	eq: Int
diff --git a/graphql/schema/wrappers.go b/graphql/schema/wrappers.go
index 70e5bda1f42..1514d234855 100644
--- a/graphql/schema/wrappers.go
+++ b/graphql/schema/wrappers.go
@@ -127,6 +127,7 @@ type Field interface {
 	Include() bool
 	Cascade() bool
 	HasCustomDirective() (bool, map[string]bool)
+	HasLambdaDirective() bool
 	Type() Type
 	SelectionSet() []Field
 	Location() x.Location
@@ -227,6 +228,9 @@ type schema struct {
 	// something like field.Directives.ForName("custom"), which results in iterating over all the
 	// directives of the field.
 	customDirectives map[string]map[string]*ast.Directive
+	// lambdaDirectives stores the mapping of typeName->fieldName->true, if the field has @lambda.
+	// It is read-only.
+	lambdaDirectives map[string]map[string]bool
 	// Map from typename to auth rules
 	authRules map[string]*TypeAuth
 }
@@ -603,34 +607,167 @@ func repeatedFieldMappings(s *ast.Schema, dgPreds map[string]map[string]string)
 	return repeatedFieldNames
 }
 
-func customMappings(s *ast.Schema) map[string]map[string]*ast.Directive {
+// customAndLambdaMappings does following things:
+// * If there is @custom on any field, it removes the directive from the list of directives on
+//	 that field. Instead, it puts it in a map of typeName->fieldName->custom directive definition.
+//	 This mapping is returned as the first return value, which is later used to determine if some
+//	 field has custom directive or not, and accordingly construct the HTTP request for the field.
+// * If there is @lambda on any field, it removes the directive from the list of directives on
+//	 that field. Instead, it puts it in a map of typeName->fieldName->bool. This mapping is returned
+//	 as the second return value, which is later used to determine if some field has lambda directive
+//	 or not. An appropriate @custom directive is also constructed for the field with @lambda and
+//	 put into the first mapping. Both of these mappings together are used to construct the HTTP
+//	 request for @lambda field. Internally, @lambda is just @custom(http: {
+//	   url: "<graphql_lambda_url: a-fixed-pre-defined-url>",
+//	   method: POST,
+//	   body: "<all-the-args-for-a-query-or-mutation>/<all-the-scalar-fields-from-parent-type-for-a
+//	   -@lambda-on-field>"
+//	   mode: BATCH (set only if @lambda was on a non query/mutation field)
+//	 })
+//	 So, by constructing an appropriate custom directive for @lambda fields,
+//	 we just reuse logic from @custom.
+func customAndLambdaMappings(s *ast.Schema) (map[string]map[string]*ast.Directive,
+	map[string]map[string]bool) {
 	customDirectives := make(map[string]map[string]*ast.Directive)
+	lambdaDirectives := make(map[string]map[string]bool)
 
 	for _, typ := range s.Types {
 		for _, field := range typ.Fields {
 			for i, dir := range field.Directives {
-				if dir.Name == customDirective {
-					// remove custom directive from s
+				if dir.Name == customDirective || dir.Name == lambdaDirective {
+					// remove @custom/@lambda directive from s
 					lastIndex := len(field.Directives) - 1
 					field.Directives[i] = field.Directives[lastIndex]
 					field.Directives = field.Directives[:lastIndex]
-					// now put it into mapping
-					var fieldMap map[string]*ast.Directive
-					if innerMap, ok := customDirectives[typ.Name]; !ok {
-						fieldMap = make(map[string]*ast.Directive)
+					// get the @custom mapping for this type
+					var customFieldMap map[string]*ast.Directive
+					if existingCustomFieldMap, ok := customDirectives[typ.Name]; ok {
+						customFieldMap = existingCustomFieldMap
+					} else {
+						customFieldMap = make(map[string]*ast.Directive)
+					}
+
+					if dir.Name == customDirective {
+						// if it was @custom, put the directive at the @custom mapping for the field
+						customFieldMap[field.Name] = dir
 					} else {
-						fieldMap = innerMap
+						// for lambda, first update the lambda directives map
+						var lambdaFieldMap map[string]bool
+						if existingLambdaFieldMap, ok := lambdaDirectives[typ.Name]; ok {
+							lambdaFieldMap = existingLambdaFieldMap
+						} else {
+							lambdaFieldMap = make(map[string]bool)
+						}
+						lambdaFieldMap[field.Name] = true
+						lambdaDirectives[typ.Name] = lambdaFieldMap
+						// then, build a custom directive with correct semantics to be put
+						// into custom directives map at this field
+						customFieldMap[field.Name] = buildCustomDirectiveForLambda(typ, field,
+							dir, func(f *ast.FieldDefinition) bool {
+								// Need to skip the fields which have a @custom/@lambda from
+								// going in body template. The field itself may not have the
+								// directive anymore because the directive may have been removed by
+								// this function already. So, using these maps to find the same.
+								return lambdaFieldMap[f.Name] || customFieldMap[f.Name] != nil
+							})
 					}
-					fieldMap[field.Name] = dir
-					customDirectives[typ.Name] = fieldMap
-					// break, as there can only be one @custom
+					// finally, update the custom directives map for this type
+					customDirectives[typ.Name] = customFieldMap
+					// break, as there can only be one @custom/@lambda
 					break
 				}
 			}
 		}
 	}
 
-	return customDirectives
+	return customDirectives, lambdaDirectives
+}
+
+func hasCustomOrLambda(f *ast.FieldDefinition) bool {
+	for _, dir := range f.Directives {
+		if dir.Name == customDirective || dir.Name == lambdaDirective {
+			return true
+		}
+	}
+	return false
+}
+
+// buildCustomDirectiveForLambda returns custom directive for the given field to be used for @lambda
+// The constructed @custom looks like this:
+//	@custom(http: {
+//	   url: "<graphql_lambda_url: a-fixed-pre-defined-url>",
+//	   method: POST,
+//	   body: "<all-the-args-for-a-query-or-mutation>/<all-the-scalar-fields-from-parent-type-for-a
+//	   -@lambda-on-field>"
+//	   mode: BATCH (set only if @lambda was on a non query/mutation field)
+//	})
+func buildCustomDirectiveForLambda(defn *ast.Definition, field *ast.FieldDefinition,
+	lambdaDir *ast.Directive, skipInBodyTemplate func(f *ast.FieldDefinition) bool) *ast.Directive {
+	comma := ""
+	var bodyTemplate strings.Builder
+
+	// this function appends a variable to the body template for @custom
+	appendToBodyTemplate := func(varName string) {
+		bodyTemplate.WriteString(comma)
+		bodyTemplate.WriteString(varName)
+		bodyTemplate.WriteString(": $")
+		bodyTemplate.WriteString(varName)
+		comma = ", "
+	}
+
+	// first let's construct the body template for the custom directive
+	bodyTemplate.WriteString("{")
+	if isQueryOrMutationType(defn) {
+		// for queries and mutations we need to put their arguments in the body template
+		for _, arg := range field.Arguments {
+			appendToBodyTemplate(arg.Name)
+		}
+	} else {
+		// For fields in other types, skip the ones in body template which have a @lambda or @custom
+		// or are not scalar. The skipInBodyTemplate function is also used to check these
+		// conditions, in case the field can't tell by itself.
+		for _, f := range defn.Fields {
+			if hasCustomOrLambda(f) || !isScalar(f.Type.Name()) || skipInBodyTemplate(f) {
+				continue
+			}
+			appendToBodyTemplate(f.Name)
+		}
+	}
+	bodyTemplate.WriteString("}")
+
+	// build the children for http argument
+	httpArgChildrens := []*ast.ChildValue{
+		getChildValue(httpUrl, x.Config.GraphqlLambdaUrl, ast.StringValue, lambdaDir.Position),
+		getChildValue(httpMethod, http.MethodPost, ast.EnumValue, lambdaDir.Position),
+		getChildValue(httpBody, bodyTemplate.String(), ast.StringValue, lambdaDir.Position),
+	}
+	if !isQueryOrMutationType(defn) {
+		httpArgChildrens = append(httpArgChildrens,
+			getChildValue(mode, BATCH, ast.EnumValue, lambdaDir.Position))
+	}
+
+	// build the custom directive
+	return &ast.Directive{
+		Name: customDirective,
+		Arguments: []*ast.Argument{{
+			Name: httpArg,
+			Value: &ast.Value{
+				Kind:     ast.ObjectValue,
+				Children: httpArgChildrens,
+				Position: lambdaDir.Position,
+			},
+			Position: lambdaDir.Position,
+		}},
+		Position: lambdaDir.Position,
+	}
+}
+
+func getChildValue(name, raw string, kind ast.ValueKind, position *ast.Position) *ast.ChildValue {
+	return &ast.ChildValue{
+		Name:     name,
+		Value:    &ast.Value{Raw: raw, Kind: kind, Position: position},
+		Position: position,
+	}
 }
 
 // AsSchema wraps a github.com/vektah/gqlparser/ast.Schema.
@@ -642,13 +779,15 @@ func AsSchema(s *ast.Schema) (Schema, error) {
 		return nil, err
 	}
 
+	customDirs, lambdaDirs := customAndLambdaMappings(s)
 	dgraphPredicate := dgraphMapping(s)
 	sch := &schema{
 		schema:             s,
 		dgraphPredicate:    dgraphPredicate,
 		typeNameAst:        typeMappings(s),
 		repeatedFieldNames: repeatedFieldMappings(s, dgraphPredicate),
-		customDirectives:   customMappings(s),
+		customDirectives:   customDirs,
+		lambdaDirectives:   lambdaDirs,
 		authRules:          authRules,
 	}
 	sch.mutatedType = mutatedTypeMapping(sch, dgraphPredicate)
@@ -822,6 +961,10 @@ func (f *field) HasCustomDirective() (bool, map[string]bool) {
 	return true, rf
 }
 
+func (f *field) HasLambdaDirective() bool {
+	return f.op.inSchema.lambdaDirectives[f.GetObjectName()][f.Name()]
+}
+
 func (f *field) XIDArg() string {
 	xidArgName := ""
 	passwordField := f.Type().PasswordField()
@@ -952,6 +1095,8 @@ func getCustomHTTPConfig(f *field, isQueryOrMutation bool) (FieldHTTPConfig, err
 	}
 
 	fconf.ForwardHeaders = http.Header{}
+	// set application/json as the default Content-Type
+	fconf.ForwardHeaders.Set("Content-Type", "application/json")
 	secretHeaders := httpArg.Value.Children.ForName("secretHeaders")
 	if secretHeaders != nil {
 		hc.RLock()
@@ -1180,6 +1325,10 @@ func (q *query) HasCustomDirective() (bool, map[string]bool) {
 	return (*field)(q).HasCustomDirective()
 }
 
+func (q *query) HasLambdaDirective() bool {
+	return (*field)(q).HasLambdaDirective()
+}
+
 func (q *query) IDArgValue() (*string, uint64, error) {
 	return (*field)(q).IDArgValue()
 }
@@ -1313,6 +1462,10 @@ func (m *mutation) HasCustomDirective() (bool, map[string]bool) {
 	return (*field)(m).HasCustomDirective()
 }
 
+func (m *mutation) HasLambdaDirective() bool {
+	return (*field)(m).HasLambdaDirective()
+}
+
 func (m *mutation) Type() Type {
 	return (*field)(m).Type()
 }
diff --git a/x/config.go b/x/config.go
index 5390720710a..8a6e78d660b 100644
--- a/x/config.go
+++ b/x/config.go
@@ -36,6 +36,8 @@ type Options struct {
 	GraphqlExtension bool
 	// GraphqlDebug will enable debug mode in GraphQL
 	GraphqlDebug bool
+	// GraphqlLambdaUrl stores the URL of lambda functions for custom GraphQL resolvers
+	GraphqlLambdaUrl string
 }
 
 // Config stores the global instance of this package's options.