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Add range response KV length as a metric #16881

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Add range response KV length as a metric #16881

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1dbb35e
Add range response KV length as a metric
tjungblu Nov 7, 2023
2b64965
alternative implementation on slow req tracing
tjungblu Nov 7, 2023
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7 changes: 7 additions & 0 deletions server/etcdserver/metrics.go
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Original file line number Diff line number Diff line change
Expand Up @@ -118,6 +118,12 @@ var (
Name: "lease_expired_total",
Help: "The total number of expired leases.",
})
rangeResponseKvCount = prometheus.NewHistogramVec(prometheus.HistogramOpts{
Namespace: "etcd",
Subsystem: "server",
Name: "range_response_kv_count",
Help: "The number of KVs returned by range calls.",
}, []string{"range_begin"})

currentVersion = prometheus.NewGaugeVec(prometheus.GaugeOpts{
Namespace: "etcd",
Expand Down Expand Up @@ -168,6 +174,7 @@ func init() {
prometheus.MustRegister(slowReadIndex)
prometheus.MustRegister(readIndexFailed)
prometheus.MustRegister(leaseExpired)
prometheus.MustRegister(rangeResponseKvCount)
prometheus.MustRegister(currentVersion)
prometheus.MustRegister(currentGoVersion)
prometheus.MustRegister(serverID)
Expand Down
5 changes: 5 additions & 0 deletions server/etcdserver/v3_server.go
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Expand Up @@ -116,6 +116,11 @@ func (s *EtcdServer) Range(ctx context.Context, r *pb.RangeRequest) (*pb.RangeRe
traceutil.Field{Key: "response_count", Value: len(resp.Kvs)},
traceutil.Field{Key: "response_revision", Value: resp.Header.Revision},
)

// collect the metric on very large responses only, because the key dimensionality might blow up Prometheus.
if rangeResponseKvCount != nil && len(resp.Kvs) > 1000 {
rangeResponseKvCount.WithLabelValues(string(r.Key)).Observe(float64(len(resp.Kvs)))
}
}
trace.LogIfLong(traceThreshold)
}(time.Now())
Expand Down