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Fix double-counting bug in promhttp.InstrumentRoundTripperCounter #1118

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merged 1 commit into from
Aug 22, 2022
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Fix double-counting bug in promhttp.InstrumentRoundTripperCounter #1118

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1 change: 0 additions & 1 deletion prometheus/promhttp/instrument_client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,6 @@ func InstrumentRoundTripperCounter(counter *prometheus.CounterVec, next http.Rou
1,
rtOpts.getExemplarFn(r.Context()),
)
counter.With(labels(code, method, r.Method, resp.StatusCode, rtOpts.extraMethods...)).Inc()
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Thinking loudly: I think the function name exemplarAdd() doesn't make it obvious the metric is incremented. Maybe renaming it to addWithExemplar() may clarify it?

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Agreed! My goal here was to fix the bug with as few changes as possible so I didn't consider changing the function name... IMO that'd best be deferred to a separate PR.

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#1120

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👍🏽 Thanks for noticing this

}
return resp, err
}
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14 changes: 14 additions & 0 deletions prometheus/promhttp/instrument_client_test.go
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Expand Up @@ -25,6 +25,7 @@ import (
"time"

"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/testutil"

dto "github.com/prometheus/client_model/go"
"google.golang.org/protobuf/proto"
Expand Down Expand Up @@ -250,6 +251,19 @@ func TestClientMiddlewareAPI_WithRequestContext(t *testing.T) {
t.Errorf("metric family %s must not be empty", mf.GetName())
}
}

// make sure counters aren't double-incremented (see #1117)
expected := `
# HELP client_api_requests_total A counter for requests from the wrapped client.
# TYPE client_api_requests_total counter
client_api_requests_total{code="200",method="get"} 1
`

if err := testutil.GatherAndCompare(reg, strings.NewReader(expected),
"client_api_requests_total",
); err != nil {
t.Fatal(err)
}
}

func TestClientMiddlewareAPIWithRequestContextTimeout(t *testing.T) {
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