Copilot commented on code in PR #3557:
URL: https://github.com/apache/brpc/pull/3557#discussion_r4068277537
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src/bvar/latency_recorder.cpp:
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@@ -235,6 +240,16 @@ int LatencyRecorder::expose(const butil::StringPiece&
prefix1,
_latency.set_debug_name(prefix);
_latency_percentile.set_debug_name(prefix);
+ // Exposing a LatencyRecorder is all-or-nothing: the prometheus exporter
+ // turns the sub-bvars below back into one summary and would happily write
+ // that summary out with empty values if only some of them made it.
+ bool expose_succeeded = false;
+ BUTIL_SCOPE_EXIT {
+ if (!expose_succeeded) {
+ hide();
+ }
+ };
Review Comment:
`DumpLatencyRecorderSuffix()` synthesizes the summary names for every
exposed bvar whose name starts with `g_server_info_prefix`, not only
`MethodStatus` (see `prometheus_metrics_service.cpp:273-286`). This new
all-or-nothing path still reserves only the child names, so a standalone
`LatencyRecorder` exposed as `rpc_server_0_foo` can coexist with a plain bvar
named `rpc_server_0_foo` or `rpc_server_0_foo_sum`; the scrape then contains
duplicate metric names. Reserve and release the synthesized names in
`LatencyRecorder::expose()`/`hide()` as well, or make the exporter synthesis
apply only to `MethodStatus`.
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