thanos-query-frontend: Enable Thanos Query Stats Propagation & cache response headers #10
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milesbxf
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Thanos Query gives us some really nice detailed internal stats - but thanos-query-frontend annoyingly blats them by trying to parse the response as a Prometheus response, which has different fields and a different structure. In addition, thanos-query-frontend doesn't even pass the &stats=all parameter through if you try to request it. This change fixes this by propagating the stats request parameter to the downstream, and decoding/encoding the Thanos Query stats structure properly. As an extra, we also set a response header if we get a cache hit so that upstreams can use this. Signed-off-by: milesbryant <[email protected]>
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milesbxf
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Nov 18, 2024
| @@ -145,8 +145,6 @@ func registerQueryFrontend(app *extkingpin.App) { | |||
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| cmd.Flag("query-frontend.log-queries-longer-than", "Log queries that are slower than the specified duration. "+ | |||
| "Set to 0 to disable. Set to < 0 to enable on all queries.").Default("0").DurationVar(&cfg.CortexHandlerConfig.LogQueriesLongerThan) | |||
| cmd.Flag("query-frontend.query-stats-enabled", "True to enable query statistics tracking. "+ | |||
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I've removed this now that we return query stats directly in the response
| @@ -84,12 +84,22 @@ message Matrix { | |||
| } | |||
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| message PrometheusResponseStats { | |||
| PrometheusResponseSamplesStats samples = 1 [(gogoproto.jsontag) = "samples"]; | |||
| } | |||
| message Timings { | |||
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This is the difference between Thanos stats and Prometheus stats responses
steg
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Nov 18, 2024
| for _, existing := range headers { | ||
| if existing.Name == newHeader.Name { | ||
| // if headers match, overwrite with the new header | ||
| existing = newHeader |
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Should this be *existing = *newHeader ?
Also, below we sort the responses by response time and then the first non-null explanation is taken rather than the last one. Is consistency between these important?
| func (resp *PrometheusInstantQueryResponse) AddHeader(key, value string) { | ||
| resp.Headers = append(resp.Headers, &PrometheusResponseHeader{Name: key, Values: []string{value}}) | ||
| } | ||
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I think we'll end up with duplicate headers if the same header key is added twice - should this check for the header already existing and either replace it or append to its values?
| @@ -217,9 +227,25 @@ func (prometheusCodec) MergeResponse(_ Request, responses ...Response) (Response | |||
| // we need to pass on all the headers for results cache gen numbers. | |||
| var resultsCacheGenNumberHeaderValues []string | |||
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| var headers []*PrometheusResponseHeader | |||
| // merge headers | |||
| for _, res := range responses { | |||
| promResponses = append(promResponses, res.(*PrometheusResponse)) | |||
| resultsCacheGenNumberHeaderValues = append(resultsCacheGenNumberHeaderValues, getHeaderValuesWithName(res, ResultsCacheGenNumberHeaderName)...) | |||
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I doubt this matters given what was happening before, but this could be out of sync with the actual headers we return in the response due to the merging below.
| // Copy Prometheus headers into http response | ||
| for _, h := range a.Headers { | ||
| for _, v := range h.Values { | ||
| if strings.HasPrefix(h.Name, "X-") { |
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Thanos Query gives us some really nice detailed internal stats - but thanos-query-frontend annoyingly blats them by trying to parse the response as a Prometheus response, which has different fields and a different structure.
In addition, thanos-query-frontend doesn't even pass the &stats=all parameter through if you try to request it.
This change fixes this by propagating the stats request parameter to the downstream, and decoding/encoding the Thanos Query stats structure properly.
As an extra, we also set a response header if we get a cache hit so that upstreams can use this.