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Remove redundant CanonicalizeHeaderKey from metadata iteration paths #2443

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Remove redundant CanonicalizeHeaderKey from metadata iteration paths #2443

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fc90a11
Remove redundant CanonicalizeHeaderKey from metadata iteration paths
kshitijsuri90 Apr 3, 2026
91c8715
Merge branch 'main' into kshitij/remove-canonicalize-metadata
bananacocodrilo Aug 20, 2026
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5 changes: 2 additions & 3 deletions transport/grpc/headers.go
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Original file line number Diff line number Diff line change
Expand Up @@ -145,8 +145,7 @@ func metadataToTransportRequest(md metadata.MD) (*transport.Request, error) {
default:
return nil, yarpcerrors.InvalidArgumentErrorf("header has more than one value: %s:%v", header, values)
}
header = transport.CanonicalizeHeaderKey(header)
// skip routing header
// gRPC metadata keys are already lowercase.
if routingHeaders[header] {
continue
}
Expand Down Expand Up @@ -221,7 +220,7 @@ func getApplicationHeaders(md metadata.MD) (transport.Headers, error) {
}
headers := transport.NewHeadersWithCapacity(md.Len())
for header, values := range md {
header = transport.CanonicalizeHeaderKey(header)
// gRPC metadata keys are already lowercase.

@MahammadAgayev MahammadAgayev Jun 19, 2026

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nit: comment is a bit confusing for first time readers, maybe rephrase as method comment, saying, "this function assumes incoming headers are lowercase because ..."

if isReserved(header) {
continue
}
Expand Down
44 changes: 43 additions & 1 deletion transport/grpc/headers_test.go
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Expand Up @@ -253,7 +253,7 @@ func TestGetApplicationHeaders(t *testing.T) {
"rpc-service": []string{"foo"}, // reserved header
"test-header-empty": []string{}, // no value
"test-header-valid-1": []string{"test-value-1"},
"test-Header-Valid-2": []string{"test-value-2"},
"test-header-valid-2": []string{"test-value-2"},
},
wantHeaders: map[string]string{
"test-header-valid-1": "test-value-1",
Expand Down Expand Up @@ -404,3 +404,45 @@ func BenchmarkIsReserved(b *testing.B) {
})
}
}

func BenchmarkMetadataToTransportRequest(b *testing.B) {
md := metadata.Pairs(
CallerHeader, "example-caller",
ServiceHeader, "example-service",
ShardKeyHeader, "example-shard-key",
RoutingKeyHeader, "example-routing-key",
RoutingDelegateHeader, "example-routing-delegate",
EncodingHeader, "raw",
CallerProcedureHeader, "example-caller-procedure",
"x-uber-source", "service-a",
"x-request-id", "abc-123",
"x-trace-id", "trace-456",
"x-custom-1", "val1",
"x-custom-2", "val2",
)

b.ResetTimer()
for range b.N {
_, _ = metadataToTransportRequest(md)
}
}

func BenchmarkGetApplicationHeaders(b *testing.B) {
md := metadata.MD{
"rpc-caller": []string{"example-caller"},
"rpc-service": []string{"example-service"},
"rpc-encoding": []string{"raw"},
"x-uber-source": []string{"service-a"},
"x-request-id": []string{"abc-123"},
"x-trace-id": []string{"trace-456"},
"x-custom-1": []string{"val1"},
"x-custom-2": []string{"val2"},
"x-custom-3": []string{"val3"},
"x-custom-4": []string{"val4"},
}

b.ResetTimer()
for range b.N {
_, _ = getApplicationHeaders(md)
}
}
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