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Let metrics libs handle the atomicity #5738

Merged
merged 6 commits into from Feb 11, 2020
Merged

Let metrics libs handle the atomicity #5738

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9fa06c8
Tune metrics middleware
Oct 28, 2019
c471560
Explain how we init the labels slice
Feb 4, 2020
efb203f
Update pkg/middlewares/metrics/metrics.go
sylr Feb 5, 2020
fd15e24
Fix comment
Feb 5, 2020
6fb5928
review: simplify.
ldez Feb 11, 2020
6adbaaf
Merge branch 'master' into metrics
Feb 11, 2020
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24 changes: 11 additions & 13 deletions pkg/middlewares/metrics/metrics.go
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Expand Up @@ -5,7 +5,6 @@ import (
"net/http"
"strconv"
"strings"
"sync/atomic"
"time"
"unicode/utf8"

Expand All @@ -27,9 +26,6 @@ const (
)

type metricsMiddleware struct {
// Important: Since this int64 field is using sync/atomic, it has to be at the top of the struct due to a bug on 32-bit platform
// See: https://golang.org/pkg/sync/atomic/ for more information
openConns int64
next http.Handler
reqsCounter gokitmetrics.Counter
reqDurationHistogram gokitmetrics.Histogram
Expand Down Expand Up @@ -78,23 +74,25 @@ func WrapServiceHandler(ctx context.Context, registry metrics.Registry, serviceN
}

func (m *metricsMiddleware) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
labels := []string{"method", getMethod(req), "protocol", getRequestProtocol(req)}
// Initialize labels slice with correct size
labels := make([]string, 0, 2*len([]string{"method", "protocol", "code"})+len(m.baseLabels))
labels = append(labels, m.baseLabels...)
// Adding 4 entries to labels
labels = append(labels, []string{"method", getMethod(req), "protocol", getRequestProtocol(req)}...)

openConns := atomic.AddInt64(&m.openConns, 1)
m.openConnsGauge.With(labels...).Set(float64(openConns))
defer func(labelValues []string) {
openConns := atomic.AddInt64(&m.openConns, -1)
m.openConnsGauge.With(labelValues...).Set(float64(openConns))
}(labels)
m.openConnsGauge.With(labels...).Add(1)
defer m.openConnsGauge.With(labels...).Add(-1)
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I restored the defer call instead of moving m.openConnsGauge.With(labels...).Add(-1) after m.next.ServeHTTP(recorder, req) because I've a scenario where, when doing a load testing of an SSE endpoint with rate limiting activated, we never go past m.next.ServeHTTP(recorder, req) and the Gauge is never decremented.

@mpl if you have an idea why I would be really interested.

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well, that suggests m.next.ServeHTTP never returns, either because of a deadlock or a blocked channel, does it not?


start := time.Now()
recorder := newResponseRecorder(rw)
start := time.Now()
m.next.ServeHTTP(recorder, req)
duration := time.Since(start).Seconds()

// Adding 2 entries to labels
labels = append(labels, "code", strconv.Itoa(recorder.getCode()))

m.reqsCounter.With(labels...).Add(1)
m.reqDurationHistogram.With(labels...).Observe(time.Since(start).Seconds())
m.reqDurationHistogram.With(labels...).Observe(duration)
}

func getRequestProtocol(req *http.Request) string {
Expand Down