Add a filter to support HTTP/JSON<->gRPC transcoding

bazel/envoy_build_system.bzl

@@ -258,14 +258,14 @@ def _proto_header(proto_path):
   return None
 
 # Envoy proto targets should be specified with this function.
-def envoy_proto_library(name, srcs = [], deps = []):
+def envoy_proto_library(name, srcs = [], deps = [], external_deps = []):
     internal_name = name + "_internal"
     cc_proto_library(
         name = internal_name,
         srcs = srcs,
         default_runtime = "//external:protobuf",
         protoc = "//external:protoc",
-        deps = deps,
+        deps = deps + [envoy_external_dep_path(dep) for dep in external_deps],
         linkstatic = 1,
     )
     # We can't use include_prefix directly in cc_proto_library, since it
@@ -278,3 +278,30 @@ def envoy_proto_library(name, srcs = [], deps = []):
         deps = [internal_name],
         linkstatic = 1,
     )
+
+# Envoy proto descriptor targets should be specified with this function.
+# This is used for testing only.
+def envoy_proto_descriptor(name, out, srcs = [], protocopts = [], external_deps = []):
+    input_files = ["$(location " + src + ")" for src in srcs]
+    include_paths = [".", PACKAGE_NAME]
+
+    if "http_api_protos" in external_deps:
+        srcs.append("@googleapis//:http_api_protos_src")
+        include_paths.append("external/googleapis")
+
+    if "well_known_protos" in external_deps:
+        srcs.append("@protobuf_bzl//:well_known_protos")
+        include_paths.append("external/protobuf_bzl/src")
+
+    options = protocopts[:]
+    options.extend(["-I" + include_path for include_path in include_paths])
+    options.append("--descriptor_set_out=$@")
+
+    cmd = "$(location //external:protoc) " + " ".join(options + input_files)
+    native.genrule(
+        name = name,
+        srcs = srcs,
+        outs = [out],
+        cmd = cmd,
+        tools = ["//external:protoc"],
+    )

bazel/repositories.bzl

@@ -116,6 +116,14 @@ def envoy_api_deps(skip_targets):
         name = "envoy_eds",
         actual = "@envoy_api//api:eds",
     )
+    native.bind(
+        name = "http_api_protos",
+        actual = "@googleapis//:http_api_protos",
+    )
+    native.bind(
+        name = "http_api_protos_genproto",
+        actual = "@googleapis//:http_api_protos_genproto",
+    )
 
 def envoy_dependencies(path = "@envoy_deps//", skip_protobuf_bzl = False, skip_targets = []):
     if not skip_protobuf_bzl:

docs/configuration/http_filters/grpc_json_transcoder_filter.rst

@@ -0,0 +1,56 @@
+.. _config_http_filters_grpc_json_transcoder:
+
+gRPC-JSON transcoder filter
+===========================
+
+gRPC :ref:`architecture overview <arch_overview_grpc>`.
+
+This is a filter which allows a RESTful JSON API client to send requests to Envoy over HTTP
+and get proxied to a gRPC service. The HTTP mapping for the gRPC service has to be defined by
+`custom options <https://cloud.google.com/service-management/reference/rpc/google.api#http>`_.
+
+Configure gRPC-JSON transcoder
+------------------------------
+
+The filter config for the filter requires the descriptor file as well as a list of the gRPC 
+services to be transcoded.
+
+.. code-block:: json
+
+  {
+    "type": "both",
+    "name": "grpc_json_transcoder",
+    "config": {
+      "proto_descriptors": "proto.pb",
+      "services": ["grpc.service.Service"]
+    }
+  }
+
+proto_descriptors
+  *(required, string)* Supplies the binary protobuf descriptor set for the gRPC services.
+  The descriptor set has to include all of the types that are used in the services. Make sure 
+  to use the ``--include_import`` option for ``protoc``.
+
+  To generate a protobuf descriptor set for the gRPC service, you'll also need to clone the
+  googleapis repository from Github before running protoc, as you'll need annotations.proto
+  in your include path.
+
+  .. code-block:: bash
+
+    git clone https://github.com/googleapis/googleapis
+    GOOGLEAPIS_DIR=<your-local-googleapis-folder>
+
+  Then run protoc to generate the descriptor set from bookstore.proto:
+
+  .. code-block:: bash
+
+    protoc -I$(GOOGLEAPIS_DIR) -I. --include_imports --include_source_info \
+      --descriptor_set_out=proto.pb test/proto/bookstore.proto
+
+  If you have more than one proto source files, you can pass all of them in one command.
+
+services
+  *(required, array)* A list of strings that supplies the service names that the
+  transcoder will translate. If the service name doesn't exist in ``proto_descriptors``, Envoy
+  will fail at startup. The ``proto_descriptors`` may contain more services than the service names
+  specified here, but they won't be translated.

docs/configuration/http_filters/http_filters.rst

@@ -10,6 +10,7 @@ HTTP filters
   fault_filter
   dynamodb_filter
   grpc_http1_bridge_filter
+  grpc_json_transcoder_filter
   grpc_web_filter
   health_check_filter
   ip_tagging_filter

docs/intro/arch_overview/grpc.rst

@@ -21,3 +21,6 @@ application layer:
   client to send requests to Envoy over HTTP/1.1 and get proxied to a gRPC server. It's under
   active development and is expected to be the successor to the gRPC :ref:`bridge filter
   <config_http_filters_grpc_bridge>`.
+* gRPC-JSON transcoder is supported by a :ref:`filter <config_http_filters_grpc_json_transcoder>`
+  that allows a RESTful JSON API client to send requests to Envoy over HTTP and get proxied to a
+  gRPC service.

source/common/grpc/BUILD

@@ -71,6 +71,25 @@ envoy_cc_library(
     ],
 )
 
+envoy_cc_library(
+    name = "json_transcoder_filter_lib",
+    srcs = ["json_transcoder_filter.cc"],
+    hdrs = ["json_transcoder_filter.h"],
+    external_deps = [
+        "path_matcher",
+        "grpc_transcoding",
+        "http_api_protos",
+    ],
+    deps = [
+        ":codec_lib",
+        ":common_lib",
+        ":transcoder_input_stream_lib",
+        "//include/envoy/http:filter_interface",
+        "//source/common/common:base64_lib",
+        "//source/common/http:headers_lib",
+    ],
+)
+
 envoy_cc_library(
     name = "grpc_web_filter_lib",
     srcs = ["grpc_web_filter.cc"],