Commit Graph

12 Commits

Author SHA1 Message Date
Aliaksandr Valialkin
cd152693c6
Revert "Exemplar support ()"
This reverts commit 5a3abfa041.

Reason for revert: exemplars aren't in wide use because they have numerous issues which prevent their adoption (see below).
Adding support for examplars into VictoriaMetrics introduces non-trivial code changes. These code changes need to be supported forever
once the release of VictoriaMetrics with exemplar support is published. That's why I don't think this is a good feature despite
that the source code of the reverted commit has an excellent quality. See https://docs.victoriametrics.com/goals/ .

Issues with Prometheus exemplars:

- Prometheus still has only experimental support for exemplars after more than three years since they were introduced.
  It stores exemplars in memory, so they are lost after Prometheus restart. This doesn't look like production-ready feature.
  See 0a2f3b3794/content/docs/instrumenting/exposition_formats.md (L153-L159)
  and https://prometheus.io/docs/prometheus/latest/feature_flags/#exemplars-storage

- It is very non-trivial to expose exemplars alongside metrics in your application, since the official Prometheus SDKs
  for metrics' exposition ( https://prometheus.io/docs/instrumenting/clientlibs/ ) either have very hard-to-use API
  for exposing histograms or do not have this API at all. For example, try figuring out how to expose exemplars
  via https://pkg.go.dev/github.com/prometheus/client_golang@v1.19.1/prometheus .

- It looks like exemplars are supported for Histogram metric types only -
  see https://pkg.go.dev/github.com/prometheus/client_golang@v1.19.1/prometheus#Timer.ObserveDurationWithExemplar .
  Exemplars aren't supported for Counter, Gauge and Summary metric types.

- Grafana has very poor support for Prometheus exemplars. It looks like it supports exemplars only when the query
  contains histogram_quantile() function. It queries exemplars via special Prometheus API -
  https://prometheus.io/docs/prometheus/latest/querying/api/#querying-exemplars - (which is still marked as experimental, btw.)
  and then displays all the returned exemplars on the graph as special dots. The issue is that this doesn't work
  in production in most cases when the histogram_quantile() is calculated over thousands of histogram buckets
  exposed by big number of application instances. Every histogram bucket may expose an exemplar on every timestamp shown on the graph.
  This makes the graph unusable, since it is litterally filled with thousands of exemplar dots.
  Neither Prometheus API nor Grafana doesn't provide the ability to filter out unneeded exemplars.

- Exemplars are usually connected to traces. While traces are good for some

I doubt exemplars will become production-ready in the near future because of the issues outlined above.

Alternative to exemplars:

Exemplars are marketed as a silver bullet for the correlation between metrics, traces and logs -
just click the exemplar dot on some graph in Grafana and instantly see the corresponding trace or log entry!
This doesn't work as expected in production as shown above. Are there better solutions, which work in production?
Yes - just use time-based and label-based correlation between metrics, traces and logs. Assign the same `job`
and `instance` labels to metrics, logs and traces, so you can quickly find the needed trace or log entry
by these labes on the time range with the anomaly on metrics' graph.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/5982
2024-07-03 16:09:18 +02:00
Aliaksandr Valialkin
a5d60ad78e
app/vmagent/remotewrite,lib/streamaggr: re-use common code in tests after 879771808b
- Export streamaggr.LoadFromData() function, so it could be used in tests outside the lib/streamaggr package.
  This allows removing a hack with creation of temporary files at TestRemoteWriteContext_TryPush_ImmutableTimeseries.

- Move common code for mustParsePromMetrics() function into lib/prompbmarshal package,
  so it could be used in tests for building []prompbmarshal.TimeSeries from string.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6205
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6206
2024-07-03 15:22:51 +02:00
Aliaksandr Valialkin
87338633b1
lib/slicesutil: add helper functions for setting slice length and extending its capacity
The added helper functions - SetLength() and ExtendCapacity() - replace error-prone code with simple function calls.
2024-05-12 11:33:49 +02:00
Ted Possible
0206a01d03
Exemplar support ()
This code adds Exemplars to VMagent and the promscrape parser adhering
to OpenMetrics Specifications. This will allow forwarding of exemplars
to Prometheus and other third party apps that support OpenMetrics specs.

---------

Signed-off-by: Ted Possible <ted_possible@cable.comcast.com>
(cherry picked from commit 5a3abfa041)
2024-05-10 13:14:17 +02:00
Aliaksandr Valialkin
d4a425af87
lib/prompbmarshal: use clear() instead of a loop for clearing tss inside ResetTimeSeries() 2024-03-03 23:40:47 +02:00
Aliaksandr Valialkin
8148cc52c9
lib/prompbmarshal: code cleanup after 8aaa828ba3 2024-02-01 21:41:10 +02:00
Aliaksandr Valialkin
6c56f49f9c
lib/prompbmarshal: return back custom protobuf marshaler for lib/prompbmarshal.WriteRequest
The easyproto-based marshaler is 2x slower than the previous custom marshaler,
so let's stick with it. This improves the performance for sending data to remote storage at vmagent
and reduces CPU usage to pre-v1.97.0 levels.
2024-02-01 06:34:46 +02:00
Aliaksandr Valialkin
724223fad4
lib/prompbmarshal: move WriteRequest proto definition to the correct place 2024-01-16 21:57:03 +02:00
Aliaksandr Valialkin
d566aa7d78
lib/prompbmarshal: switch to github.com/VictoriaMetrics/easyproto 2024-01-16 20:48:30 +02:00
Aliaksandr Valialkin
d962568e93 all: use %w instead of %s for wrapping errors in fmt.Errorf
This will simplify examining the returned errors such as httpserver.ErrorWithStatusCode .
See https://blog.golang.org/go1.13-errors for details.
2020-06-30 23:33:46 +03:00
Aliaksandr Valialkin
3b0f66a227 app/vmagent: fix a bug with improper relabeling when multiple -remoteWrite.urlRelableConfig args are set
This bug could result in incorrect relabeling and metrics' drop.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/467
2020-05-12 22:03:45 +03:00
Aliaksandr Valialkin
7ee7614e90 app/vmagent: initial implementation for vmagent 2020-02-23 17:31:54 +02:00