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transport: avoid slice reallocation during header creation #8547

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Merged
merged 2 commits into from
Sep 11, 2025
Merged

transport: avoid slice reallocation during header creation #8547

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552d8bb
avoid slice reallocation during header creation
arjan-bal Sep 1, 2025
90e91b9
Include more checks while computing slice size
arjan-bal Sep 10, 2025
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8 changes: 7 additions & 1 deletion internal/transport/http2_client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -556,6 +556,13 @@ func (t *http2Client) createHeaderFields(ctx context.Context, callHdr *CallHdr)
// Make the slice of certain predictable size to reduce allocations made by append.
hfLen := 7 // :method, :scheme, :path, :authority, content-type, user-agent, te
hfLen += len(authData) + len(callAuthData)
registeredCompressors := t.registeredCompressors
if registeredCompressors != "" {
hfLen++
}
if _, ok := ctx.Deadline(); ok {
hfLen++
}
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Does it make sense to also check for callHdr.SendCompress != "" and callHdr.PreviousAttempts > 0 and increment as well?

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Added these checks as well.

I only added the grpc-timeout header initially since it was the one showing up in the profiles while running the benchmark. This was probably because compression was disabled and retries can't be configured in the benchmark. The improvements were similar after adding checks for the two conditions mentioned above and running the benchmark again with compression enabled.

headerFields := make([]hpack.HeaderField, 0, hfLen)
headerFields = append(headerFields, hpack.HeaderField{Name: ":method", Value: "POST"})
headerFields = append(headerFields, hpack.HeaderField{Name: ":scheme", Value: t.scheme})
Expand All @@ -568,7 +575,6 @@ func (t *http2Client) createHeaderFields(ctx context.Context, callHdr *CallHdr)
headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-previous-rpc-attempts", Value: strconv.Itoa(callHdr.PreviousAttempts)})
}

registeredCompressors := t.registeredCompressors
if callHdr.SendCompress != "" {
headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-encoding", Value: callHdr.SendCompress})
// Include the outgoing compressor name when compressor is not registered
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