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Merged
jensneuse merged 9 commits into from
Feb 18, 2026
Merged

fix(router): fix singleflight deduplication bugs and propagate response headers #2522

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5e5d2ee
feat(router): fix singleflight deduplication bugs and propagate respo…
jensneuse Feb 18, 2026
9bcca0e
chore: harden test assertions and add documentation comments
jensneuse Feb 18, 2026
01766f9
chore: fix data race in Set rule, extract test helper
jensneuse Feb 18, 2026
0552d0e
fix(router): avoid double-applying response header rules for singlefl…
jensneuse Feb 18, 2026
154cf10
fix(router): apply response header rules only in OnFinished, not OnOr…
jensneuse Feb 18, 2026
ac919fa
chore(deps): upgrade graphql-go-tools to v2.0.0-rc.251
jensneuse Feb 18, 2026
7102873
fix(router): apply response header rules before tracing/metrics early…
jensneuse Feb 18, 2026
cda169c
test(router): add singleflight tests for propagate rules and multi-su…
jensneuse Feb 18, 2026
a7396cd
chore: address PR review nits
jensneuse Feb 18, 2026
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2 changes: 1 addition & 1 deletion router-tests/go.mod
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ require (
github.com/wundergraph/cosmo/demo/pkg/subgraphs/projects v0.0.0-20250715110703-10f2e5f9c79e
github.com/wundergraph/cosmo/router v0.0.0-20260213130455-6e3277e7b850
github.com/wundergraph/cosmo/router-plugin v0.0.0-20250808194725-de123ba1c65e
github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.250
github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.251
go.opentelemetry.io/otel v1.36.0
go.opentelemetry.io/otel/sdk v1.36.0
go.opentelemetry.io/otel/sdk/metric v1.36.0
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4 changes: 2 additions & 2 deletions router-tests/go.sum
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Original file line number Diff line number Diff line change
Expand Up @@ -354,8 +354,8 @@ github.com/wundergraph/astjson v1.0.0 h1:rETLJuQkMWWW03HCF6WBttEBOu8gi5vznj5KEUP
github.com/wundergraph/astjson v1.0.0/go.mod h1:h12D/dxxnedtLzsKyBLK7/Oe4TAoGpRVC9nDpDrZSWw=
github.com/wundergraph/go-arena v1.1.0 h1:9+wSRkJAkA2vbYHp6s8tEGhPViRGQNGXqPHT0QzhdIc=
github.com/wundergraph/go-arena v1.1.0/go.mod h1:ROOysEHWJjLQ8FSfNxZCziagb7Qw2nXY3/vgKRh7eWw=
github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.250 h1:dggpvV2VI+2zMVXRm/1NsasT7Nxne6SRYR+GSshl5P8=
github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.250/go.mod h1:MFbY0QI8ncF60DHs7yyyiyyhWyld0WE1JokiyTVY8j4=
github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.251 h1:avZIXjYGTLliqS+RCZXlnFAaJdEr9HizulP1qhNLR1U=
github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.251/go.mod h1:MFbY0QI8ncF60DHs7yyyiyyhWyld0WE1JokiyTVY8j4=
github.com/xrash/smetrics v0.0.0-20250705151800-55b8f293f342 h1:FnBeRrxr7OU4VvAzt5X7s6266i6cSVkkFPS0TuXWbIg=
github.com/xrash/smetrics v0.0.0-20250705151800-55b8f293f342/go.mod h1:Ohn+xnUBiLI6FVj/9LpzZWtj1/D6lUovWYBkxHVV3aM=
github.com/yosida95/uritemplate/v3 v3.0.2 h1:Ed3Oyj9yrmi9087+NczuL5BwkIc4wvTb5zIM+UJPGz4=
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350 changes: 350 additions & 0 deletions router-tests/singleflight_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -869,4 +869,354 @@ func TestSingleFlight(t *testing.T) {
require.Equal(t, numOfOperations, globalRequests)
})
})
t.Run("different variables with warm cache should not collide in inbound dedup", func(t *testing.T) {
t.Parallel()
testenv.Run(t, &testenv.Config{
Subgraphs: testenv.SubgraphsConfig{
GlobalDelay: time.Millisecond * 100,
},
RouterOptions: []core.Option{
core.WithEngineExecutionConfig(config.EngineExecutionConfiguration{
EnableSingleFlight: true,
ForceEnableSingleFlight: false,
EnableInboundRequestDeduplication: true,
MaxConcurrentResolvers: 0,
}),
},
}, func(t *testing.T, xEnv *testenv.Environment) {
variableValues := []int{1, 2, 3, 4, 5}

// Phase 1: Warm the variables normalization cache with sequential requests
for _, id := range variableValues {
res := xEnv.MakeGraphQLRequestOK(testenv.GraphQLRequest{
Query: `query($id: Int!) { employee(id: $id) { id details { forename } } }`,
Variables: []byte(fmt.Sprintf(`{"id": %d}`, id)),
})
v, err := astjson.Parse(res.Body)
require.NoError(t, err)
emp := v.Get("data", "employee")
require.NotNil(t, emp, "expected employee object in response for id=%d", id)
require.Equal(t, id, emp.GetInt("id"))
}

// Phase 2: Send concurrent requests with different variables (cache is now warm)
// Without the fix, all cache-hit requests get VariablesHash=0, causing them to
// collide in the inbound singleflight and return wrong data.
numPerVariable := 2
total := numPerVariable * len(variableValues)
var (
ready, done sync.WaitGroup
)
ready.Add(total)
done.Add(total)
trigger := make(chan struct{})

type result struct {
body string
requested int
}
results := make([]result, total)

idx := 0
for _, id := range variableValues {
for j := 0; j < numPerVariable; j++ {
go func(slot, varVal int) {
ready.Done()
defer done.Done()
<-trigger
res := xEnv.MakeGraphQLRequestOK(testenv.GraphQLRequest{
Query: `query($id: Int!) { employee(id: $id) { id details { forename } } }`,
Variables: []byte(fmt.Sprintf(`{"id": %d}`, varVal)),
})
results[slot] = result{body: res.Body, requested: varVal}
}(idx, id)
idx++
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}
}
ready.Wait()
close(trigger)
done.Wait()

// Verify each response matches its requested variable (no cross-contamination)
for _, r := range results {
v, err := astjson.Parse(r.body)
require.NoError(t, err)
emp := v.Get("data", "employee")
require.NotNil(t, emp, "expected employee object in response for id=%d", r.requested)
actualID := emp.GetInt("id")
require.Equal(t, r.requested, actualID,
"response for variable id=%d returned employee id=%d (cross-contamination)", r.requested, actualID)
}
})
})
t.Run("response header set rule with singleflight followers", func(t *testing.T) {
t.Parallel()
testenv.Run(t, &testenv.Config{
Subgraphs: testenv.SubgraphsConfig{
GlobalDelay: time.Millisecond * 100,
},
RouterOptions: []core.Option{
core.WithEngineExecutionConfig(config.EngineExecutionConfiguration{
EnableSingleFlight: true,
MaxConcurrentResolvers: 0,
}),
core.WithHeaderRules(config.HeaderRules{
All: &config.GlobalHeaderRule{
Response: []*config.ResponseHeaderRule{
{
Operation: config.HeaderRuleOperationSet,
Name: "X-Custom-Header",
Value: "test-value",
},
},
},
}),
},
}, func(t *testing.T, xEnv *testenv.Environment) {
responses := runConcurrentSingleflightRequests(t, xEnv, `{ employee(id: 1) { id } }`, 5)
for i, res := range responses {
require.Equal(t, `{"data":{"employee":{"id":1}}}`, res.Body)
require.Equal(t, "test-value", res.Response.Header.Get("X-Custom-Header"),
"response %d missing X-Custom-Header", i)
}
})
})
t.Run("cache control propagation with singleflight followers", func(t *testing.T) {
t.Parallel()
testenv.Run(t, &testenv.Config{
CacheControlPolicy: config.CacheControlPolicy{
Enabled: true,
Value: "max-age=300",
},
Subgraphs: testenv.SubgraphsConfig{
GlobalDelay: time.Millisecond * 100,
Employees: testenv.SubgraphConfig{
Middleware: func(handler http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Cache-Control", "max-age=120")
handler.ServeHTTP(w, r)
})
},
},
},
RouterOptions: []core.Option{
core.WithEngineExecutionConfig(config.EngineExecutionConfiguration{
EnableSingleFlight: true,
MaxConcurrentResolvers: 0,
}),
},
}, func(t *testing.T, xEnv *testenv.Environment) {
// Verify single request works
res := xEnv.MakeGraphQLRequestOK(testenv.GraphQLRequest{
Query: `{ employee(id: 1) { id } }`,
})
require.Equal(t, "max-age=120", res.Response.Header.Get("Cache-Control"), "single request should have Cache-Control")

responses := runConcurrentSingleflightRequests(t, xEnv, `{ employee(id: 1) { id } }`, 5)
for i, res := range responses {
require.Equal(t, "max-age=120", res.Response.Header.Get("Cache-Control"),
"response %d has wrong Cache-Control header", i)
}
})
})
t.Run("multiple response set rules with singleflight followers", func(t *testing.T) {
t.Parallel()
testenv.Run(t, &testenv.Config{
Subgraphs: testenv.SubgraphsConfig{
GlobalDelay: time.Millisecond * 100,
},
RouterOptions: []core.Option{
core.WithEngineExecutionConfig(config.EngineExecutionConfiguration{
EnableSingleFlight: true,
MaxConcurrentResolvers: 0,
}),
core.WithHeaderRules(config.HeaderRules{
All: &config.GlobalHeaderRule{
Response: []*config.ResponseHeaderRule{
{
Operation: config.HeaderRuleOperationSet,
Name: "X-Header-A",
Value: "value-a",
},
{
Operation: config.HeaderRuleOperationSet,
Name: "X-Header-B",
Value: "value-b",
},
},
},
}),
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},
}, func(t *testing.T, xEnv *testenv.Environment) {
// Verify single request works
res := xEnv.MakeGraphQLRequestOK(testenv.GraphQLRequest{
Query: `{ employee(id: 1) { id } }`,
})
require.Equal(t, "value-a", res.Response.Header.Get("X-Header-A"), "single request should have X-Header-A")
require.Equal(t, "value-b", res.Response.Header.Get("X-Header-B"), "single request should have X-Header-B")

responses := runConcurrentSingleflightRequests(t, xEnv, `{ employee(id: 1) { id } }`, 5)
for i, res := range responses {
require.Equal(t, "value-a", res.Response.Header.Get("X-Header-A"),
"response %d missing X-Header-A", i)
require.Equal(t, "value-b", res.Response.Header.Get("X-Header-B"),
"response %d missing X-Header-B", i)
}
})
})
t.Run("multi-subgraph response header propagation with singleflight", func(t *testing.T) {
t.Parallel()
testenv.Run(t, &testenv.Config{
Subgraphs: testenv.SubgraphsConfig{
GlobalDelay: time.Millisecond * 100,
},
RouterOptions: []core.Option{
core.WithEngineExecutionConfig(config.EngineExecutionConfiguration{
EnableSingleFlight: true,
MaxConcurrentResolvers: 0,
}),
core.WithHeaderRules(config.HeaderRules{
All: &config.GlobalHeaderRule{
Response: []*config.ResponseHeaderRule{
{
Operation: config.HeaderRuleOperationSet,
Name: "X-Custom-Header",
Value: "multi-subgraph-value",
},
},
},
}),
},
}, func(t *testing.T, xEnv *testenv.Environment) {
// This query fans out to multiple subgraphs: employees, family, availability, mood
query := `{ employee(id: 1) { id details { forename surname } isAvailable currentMood } }`

responses := runConcurrentSingleflightRequests(t, xEnv, query, 5)
for i, res := range responses {
require.Contains(t, res.Body, `"employee"`)
require.Equal(t, "multi-subgraph-value", res.Response.Header.Get("X-Custom-Header"),
"response %d missing X-Custom-Header from multi-subgraph query", i)
}
})
})
t.Run("subgraph-specific response header rule with singleflight", func(t *testing.T) {
t.Parallel()
testenv.Run(t, &testenv.Config{
Subgraphs: testenv.SubgraphsConfig{
GlobalDelay: time.Millisecond * 100,
},
RouterOptions: []core.Option{
core.WithEngineExecutionConfig(config.EngineExecutionConfiguration{
EnableSingleFlight: true,
MaxConcurrentResolvers: 0,
}),
core.WithHeaderRules(config.HeaderRules{
Subgraphs: map[string]*config.GlobalHeaderRule{
"employees": {
Response: []*config.ResponseHeaderRule{
{
Operation: config.HeaderRuleOperationSet,
Name: "X-Subgraph-Header",
Value: "employees-value",
},
},
},
},
}),
},
}, func(t *testing.T, xEnv *testenv.Environment) {
// This query hits the employees subgraph, so the subgraph-specific rule should apply
responses := runConcurrentSingleflightRequests(t, xEnv, `{ employees { id } }`, 5)
for i, res := range responses {
require.Equal(t, `{"data":{"employees":[{"id":1},{"id":2},{"id":3},{"id":4},{"id":5},{"id":7},{"id":8},{"id":10},{"id":11},{"id":12}]}}`, res.Body)
require.Equal(t, "employees-value", res.Response.Header.Get("X-Subgraph-Header"),
"response %d missing subgraph-specific X-Subgraph-Header", i)
}
})
})
t.Run("mixed global and subgraph-specific response header rules with singleflight", func(t *testing.T) {
t.Parallel()
testenv.Run(t, &testenv.Config{
Subgraphs: testenv.SubgraphsConfig{
GlobalDelay: time.Millisecond * 100,
},
RouterOptions: []core.Option{
core.WithEngineExecutionConfig(config.EngineExecutionConfiguration{
EnableSingleFlight: true,
MaxConcurrentResolvers: 0,
}),
core.WithHeaderRules(config.HeaderRules{
All: &config.GlobalHeaderRule{
Response: []*config.ResponseHeaderRule{
{
Operation: config.HeaderRuleOperationSet,
Name: "X-Global-Header",
Value: "global-value",
},
},
},
Subgraphs: map[string]*config.GlobalHeaderRule{
"employees": {
Response: []*config.ResponseHeaderRule{
{
Operation: config.HeaderRuleOperationSet,
Name: "X-Employees-Header",
Value: "employees-value",
},
},
},
"family": {
Response: []*config.ResponseHeaderRule{
{
Operation: config.HeaderRuleOperationSet,
Name: "X-Family-Header",
Value: "family-value",
},
},
},
},
}),
},
}, func(t *testing.T, xEnv *testenv.Environment) {
// This query fans out to employees (root) and family (entity resolution for hasChildren)
query := `{ employee(id: 1) { id details { forename hasChildren } } }`

responses := runConcurrentSingleflightRequests(t, xEnv, query, 5)
for i, res := range responses {
require.Contains(t, res.Body, `"employee"`)
require.Equal(t, "global-value", res.Response.Header.Get("X-Global-Header"),
"response %d missing global X-Global-Header", i)
require.Equal(t, "employees-value", res.Response.Header.Get("X-Employees-Header"),
"response %d missing subgraph-specific X-Employees-Header", i)
require.Equal(t, "family-value", res.Response.Header.Get("X-Family-Header"),
"response %d missing subgraph-specific X-Family-Header", i)
}
})
})
}

// runConcurrentSingleflightRequests sends n identical GraphQL requests concurrently,
// using a barrier to maximize overlap and trigger singleflight deduplication.
func runConcurrentSingleflightRequests(t *testing.T, xEnv *testenv.Environment, query string, n int) []*testenv.TestResponse {
t.Helper()
var ready, done sync.WaitGroup
ready.Add(n)
done.Add(n)
trigger := make(chan struct{})
responses := make([]*testenv.TestResponse, n)
for i := 0; i < n; i++ {
go func(idx int) {
ready.Done()
defer done.Done()
<-trigger
resp, err := xEnv.MakeGraphQLRequest(testenv.GraphQLRequest{Query: query})
require.NoError(t, err)
require.Equal(t, http.StatusOK, resp.Response.StatusCode)
responses[idx] = resp
}(i)
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}
ready.Wait()
close(trigger)
done.Wait()
return responses
}
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