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Add Exemplars for http_request_duration_seconds histogram #3977

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merged 1 commit into from Mar 26, 2021

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metalmatze
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@metalmatze metalmatze commented Mar 26, 2021

  • I added CHANGELOG entry for this change.
  • Change is not relevant to the end user.

Changes

The Prometheus HTTP handler now enables OpenMetrics as response format upon content negotiation.
You can test it by running curl -s -H 'Accept: application/openmetrics-text' localhost:10904/metrics
This allows us to pass a traceID to ObserveWithExemplar.

A lot of the other changes are actually changing the order of calling the middlewares.
Going forward we need to make sure to first call the tracing middleware so that by the time our monitoring/instrumentation middleware gets hit the tracing spans are already populated.

Verification

Tested locally with Jaeger and Prometheus running --enable-feature=exemplar-storage.

Screenshot from 2021-03-26 12-47-25

Closes #3944

@metalmatze metalmatze requested a review from yeya24 March 26, 2021 11:49
Signed-off-by: Matthias Loibl <mail@matthiasloibl.com>

A lot of these changes are actually changing the order of calling the
middlwares. Going forward we need to make sure to first call the tracing
middleware so that by the time our monitoring/instrumentation middleware
gets hit the tracing spans are already populated.
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This is sooo good. Thanks @metalmatze !

pkg/extprom/http/instrument_server.go Show resolved Hide resolved
@bwplotka bwplotka merged commit 3016237 into thanos-io:main Mar 26, 2021
@metalmatze metalmatze deleted the exemplars branch March 26, 2021 12:35
// If we find a tracingID we'll expose it as Exemplar.
span := opentracing.SpanFromContext(r.Context())
if span != nil {
spanCtx, ok := span.Context().(jaeger.SpanContext)
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Here we just support Jaeger tracer? Is it compatible with lightstep, stackdriver, etc?

if span != nil {
spanCtx, ok := span.Context().(jaeger.SpanContext)
if ok {
observer.(prometheus.ExemplarObserver).ObserveWithExemplar(
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Like in the weaveworks example https://github.com/weaveworks/common/pull/202/files#diff-29d7cb6219a01fc80b731ac8004ac0f5edd5a1be507b164939ba4a4d1caf9ac2R70, I think we also need to check for sampled trace ID.

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Let's iterate over it @yeya24 good points. Also I would see GetTraceID as some helper function tbh (:

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Instrument http_request_duration_seconds metric with exemplars
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