Fix errors in tutorial/instrumenting HTTP server #2815

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1. jan--f

   added

   kind/bugDocumentation errors, broken links, incorrect informationDocumentation errors, broken links, incorrect information

   on Jan 20, 2026
2. santhiprakash

   added a commit that references this issue on Sep 2, 2026

   docs: fix stale explanation in instrumenting HTTP server tutorial

   ...

   This issue will close once commit d6072aa is merged into the 'main' branch.

   d6072aa
3. santhiprakash commented on Oct 1, 2026

   

   santhiprakash

   on Oct 1, 2026

   Contributor

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   I compared the tutorial prose in docs/tutorials/instrumenting_http_server_in_go.md against the sample code on current main (605cf81). Three statements still contradict the code:

   1. L87: "The prometheus.MustRegister function registers the pingCounter with the default registry." — the sample code doesn't call MustRegister anywhere; main() creates a custom registry (reg := prometheus.NewRegistry(), L78/L128) and the counter is registered through promauto.With(reg) (L53/L111).

   2. L89: "promhttp.Handler() provides an http.Handler which exposes the metrics registered in the default registry." — the code uses promhttp.HandlerFor(reg, promhttp.HandlerOpts{}) (L82/L132), which serves the custom registry, not the default one.

   3. L150: "The default registry comes with a collector for Go runtime metrics, and that is why we see other metrics like go_threads, go_goroutines, etc." — a bare prometheus.NewRegistry() starts empty and no Go collector is registered in the sample, so running the tutorial as written only exposes ping_request_count. The go_*/promhttp_* series in ping_metric.png look like they date from before the tutorial switched to a custom registry (292bc32).

   Is fixing these three sentences the remaining scope of this issue, or was the grammar-only pass #2824 considered sufficient? Happy to put together a PR if it's still wanted.