Fix remote write receiver endpoint for exemplars #9414
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@csmarchbanks and @cstyan this PR is ready for review. Thank you in advance. |
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@csmarchbanks, @cstyan and @codesome friendly reminder: this PR is ready for review. Thank you in advance! 😃 |
csmarchbanks
requested changes
Oct 20, 2021
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So, I think your previous code in write_handler was actually correct, the problem is that AppendExemplar will not try to find an existing series with the passed in labels if the ref is not found. A couple options that I can see:
- Change (*headAppender).AppendExemplar to use
getByHashin addition togetByID. - Expose/use GetRef, but that would likely involve some interface changes or casting, I would prefer the other option.
cc: @codesome, does option 1 seem reasonable to you?
storage/remote/write_handler.go
Outdated
| if exemplarErr != nil { | ||
| // Since exemplar storage is still experimental, we don't fail the request on ingestion errors. | ||
| level.Debug(h.logger).Log("msg", "Error while adding exemplar in AddExemplar", "exemplar", fmt.Sprintf("%+v", e), "err", exemplarErr) | ||
| if index < len(ts.Exemplars) { |
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I don't think this will work, as there is no guarantee that the order of samples and exemplars in a single request are the same. Or if they correspond to each other at all.
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I modified the function (*headAppender).AppendExemplar with the following code:
// Get Series
s := a.head.series.getByID(ref)
if s == nil {
s = a.head.series.getByHash(lset.Hash(), lset)
}
if s == nil {
return 0, fmt.Errorf("unknown series ref. when trying to add exemplar: %d", ref)
}However, I've got panic on app.Commit():
ts=2021-10-21T14:54:34.632Z caller=web.go:96 level=error component=web msg="panic while serving request" client=172.17.0.29:52792 url=/api/v1/write err="runtime error: invalid memory address or nil pointer dereference" stack="goroutine 501 [running]:\ngithub.com/prometheus/prometheus/web.withStackTracer.func1.1()\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/web/web.go:95 +0x99\npanic({0x269aa60, 0x4b81600})\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/runtime/panic.go:1038 +0x215\ngithub.com/opentracing-contrib/go-stdlib/nethttp.MiddlewareFunc.func5.1()\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/vendor/github.com/opentracing-contrib/go-stdlib/nethttp/server.go:150 +0x139\npanic({0x269aa60, 0x4b81600})\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/runtime/panic.go:1038 +0x215\ngithub.com/prometheus/prometheus/tsdb.(*headAppender).Commit(0xc00224bae0)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/tsdb/head_append.go:417 +0x8b6\ngithub.com/prometheus/prometheus/tsdb.dbAppender.Commit({{0x345f908, 0xc00224bae0}, 0xc000954780})\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/tsdb/db.go:871 +0x35\ngithub.com/prometheus/prometheus/storage.(*fanoutAppender).Commit(0xc00224ed80)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/storage/fanout.go:176 +0x3f\ngithub.com/prometheus/prometheus/storage/remote.(*writeHandler).write.func1()\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/storage/remote/write_handler.go:94 +0x31\ngithub.com/prometheus/prometheus/storage/remote.(*writeHandler).write(0xc000735160, {0x345ec58, 0xc002237410}, 0xc00223dc20)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/storage/remote/write_handler.go:125 +0x24e\ngithub.com/prometheus/prometheus/storage/remote.(*writeHandler).ServeHTTP(0xc000735160, {0x7fd3fd324ad8, 0xc00223dbd0}, 0xc002256900)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/storage/remote/write_handler.go:52 +0xb3\ngithub.com/prometheus/prometheus/web/api/v1.(*API).remoteWrite(0xc002237470, {0x7fd3fd324ad8, 0xc00223dbd0}, 0x340d140)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/web/api/v1/api.go:1383 +0x37\ngithub.com/prometheus/prometheus/web.(*Handler).testReady.func1({0x7fd3fd324ad8, 0xc00223dbd0}, 0xc00223dbd0)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/web/web.go:522 +0x39\nnet/http.HandlerFunc.ServeHTTP(0x7fd3fd324ad8, {0x7fd3fd324ad8, 0xc00223dbd0}, 0xc00049a000)\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/net/http/server.go:2046 +0x2f\ngithub.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerResponseSize.func1({0x7fd3fd324ad8, 0xc00223db80}, 0xc002256900)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_server.go:198 +0xa3\nnet/http.HandlerFunc.ServeHTTP(0x340d1a0, {0x7fd3fd324ad8, 0xc00223db80}, 0xc002237440)\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/net/http/server.go:2046 +0x2f\ngithub.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerDuration.func2({0x7fd3fd324ad8, 0xc00223db80}, 0xc002256900)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_server.go:76 +0xa2\nnet/http.HandlerFunc.ServeHTTP(0x3448120, {0x7fd3fd324ad8, 0xc00223db80}, 0x0)\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/net/http/server.go:2046 +0x2f\ngithub.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerCounter.func1({0x3448120, 0xc00223db30}, 0xc002256900)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_server.go:101 +0x92\ngithub.com/prometheus/prometheus/web.setPathWithPrefix.func1.1({0x3448120, 0xc00223db30}, 0xc002256800)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/web/web.go:1146 +0x290\ngithub.com/prometheus/common/route.(*Router).handle.func1({0x3448120, 0xc00223db30}, 0xc002256700, {0x0, 0x0, 0xc0009940c0})\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/vendor/github.com/prometheus/common/route/route.go:83 +0x2ae\ngithub.com/julienschmidt/httprouter.(*Router).ServeHTTP(0xc0007961e0, {0x3448120, 0xc00223db30}, 0xc002256700)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/vendor/github.com/julienschmidt/httprouter/router.go:387 +0x84b\ngithub.com/prometheus/common/route.(*Router).ServeHTTP(0x10, {0x3448120, 0xc00223db30}, 0x1)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/vendor/github.com/prometheus/common/route/route.go:126 +0x26\nnet/http.StripPrefix.func1({0x3448120, 0xc00223db30}, 0xc002256600)\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/net/http/server.go:2089 +0x330\nnet/http.HandlerFunc.ServeHTTP(0x7fd3fd073a70, {0x3448120, 0xc00223db30}, 0x7fd42414dd28)\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/net/http/server.go:2046 +0x2f\nnet/http.(*ServeMux).ServeHTTP(0x40d187, {0x3448120, 0xc00223db30}, 0xc002256600)\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/net/http/server.go:2424 +0x149\ngithub.com/opentracing-contrib/go-stdlib/nethttp.MiddlewareFunc.func5({0x3446c50, 0xc00183e700}, 0xc001ee0d00)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/vendor/github.com/opentracing-contrib/go-stdlib/nethttp/server.go:154 +0x62d\nnet/http.HandlerFunc.ServeHTTP(0x0, {0x3446c50, 0xc00183e700}, 0xc0017b8fc0)\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/net/http/server.go:2046 +0x2f\ngithub.com/prometheus/prometheus/web.withStackTracer.func1({0x3446c50, 0xc00183e700}, 0xc001fd0600)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/web/web.go:100 +0x97\nnet/http.HandlerFunc.ServeHTTP(0x7ffea9fd2f0f, {0x3446c50, 0xc00183e700}, 0x90)\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/net/http/server.go:2046 +0x2f\ngithub.com/prometheus/exporter-toolkit/web.(*webHandler).ServeHTTP(0xc000995980, {0x3446c50, 0xc00183e700}, 0x40)\n\t/home/scatudal/go/src/github.com/prometheus/prometheus/vendor/github.com/prometheus/exporter-toolkit/web/handler.go:101 +0x852\nnet/http.serverHandler.ServeHTTP({0x3439928}, {0x3446c50, 0xc00183e700}, 0xc001ee0d00)\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/net/http/server.go:2878 +0x43b\nnet/http.(*conn).serve(0xc0018b7e00, {0x345ec58, 0xc000e9b740})\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/net/http/server.go:1929 +0xb08\ncreated by net/http.(*Server).Serve\n\t/home/linuxbrew/.linuxbrew/opt/go/libexec/src/net/http/server.go:3033 +0x4e8\n"
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Did you also update the ref when the exemplar is actually added? E.g. update
a.exemplars = append(a.exemplars, exemplarWithSeriesRef{ref, e})
to
a.exemplars = append(a.exemplars, exemplarWithSeriesRef{s.ref, e})
or maybe just set ref = s.ref after the getByHash call to make sure no one accidentally uses the wrong ref in the future.
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so with this code, I don't have anymore panics and it seems to work:
// Get Series
s := a.head.series.getByID(ref)
if s == nil {
s = a.head.series.getByHash(lset.Hash(), lset)
if s != nil {
ref = s.ref
}
}
if s == nil {
return 0, fmt.Errorf("unknown series ref. when trying to add exemplar: %d", ref)
}Example:
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@codesome does the code change described above for the function (*headAppender).AppendExemplar would be acceptable?
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Updated the code of this PR with the proposed fix
Signed-off-by: Serge Catudal <[email protected]>
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Thanks! If you feel like a test would be nice, feel free to open a followup PR. I am merging this to cut the release candidate. |
Rudy167
pushed a commit
to Rudy167/prometheus
that referenced
this pull request
Oct 26, 2021
Signed-off-by: Serge Catudal <[email protected]> Signed-off-by: “Amit” <“[email protected]”>
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Signed-off-by: Serge Catudal [email protected]
Previous support for exemplars on the remote write receiver endpoint was triggering the following error:
This PR aims to fix the problem.
Tested locally using a modified version of the opentelemetry-collector-contrib prometheusremotewriteexporter to send metrics with exemplars.
Here is a screenshot of exemplars received by the remote write receiver endpoint:
