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Add gRPC render metadata header #538

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Add gRPC render metadata header #538

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Add gRPC render metadata header 
In headers, we now send the number of metrics gRPC render will
stream. This can be beneficial for the receiver to know how many
metrics it will receive over the stream.
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@emadolsky
emadolsky committed Feb 20, 2023
commit 673822e9c895498d8d27961501e4f80bba89f0d6
13 changes: 13 additions & 0 deletions carbonserver/render.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ import (

"go.uber.org/zap"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/peer"
"google.golang.org/grpc/status"

Expand Down Expand Up @@ -646,6 +647,13 @@ func (listener *CarbonserverListener) streamMetrics(stream grpcv2.CarbonV2_Rende
return
}

const gRPCRenderMetricsCountHeaderKey = "metrics-count"

func sendRenderMetadataHeader(stream grpcv2.CarbonV2_RenderServer, filesCount int) error {
header := metadata.Pairs(gRPCRenderMetricsCountHeaderKey, strconv.Itoa(filesCount))
return stream.SendHeader(header)
}

// Render implements Render rpc of CarbonV2 gRPC service
func (listener *CarbonserverListener) Render(req *protov2.MultiFetchRequest, stream grpcv2.CarbonV2_RenderServer) (rpcErr error) {
t0 := time.Now()
Expand Down Expand Up @@ -726,6 +734,10 @@ func (listener *CarbonserverListener) Render(req *protov2.MultiFetchRequest, str
metricGlobMap := getMetricGlobMapFromExpandedGlobs(expandedGlobs)
tle.MetricGlobMapLength = len(metricGlobMap)
filesCount := countFilesInExpandedGlobs(expandedGlobs)
err = sendRenderMetadataHeader(stream, filesCount)
if err != nil {
return nil, err
}
prepareChan := make(chan response, getStreamingChannelSize(filesCount))
go func() {
prepareT0 := time.Now()
Expand Down Expand Up @@ -768,6 +780,7 @@ func (listener *CarbonserverListener) Render(req *protov2.MultiFetchRequest, str
case res != nil:
atomic.AddUint64(&listener.metrics.QueryCacheHit, 1)
cachedResponses := res.([]response)
err = sendRenderMetadataHeader(stream, len(cachedResponses))
responseChanToStream = make(chan response, getStreamingChannelSize(len(cachedResponses)))
go func() {
for _, r := range cachedResponses {
Expand Down