otelhttp: Deprecate WithMetricAttributesFn in favor of Labeler#8587
Merged
pellared merged 6 commits intoopen-telemetry:mainfrom Mar 2, 2026
Merged
otelhttp: Deprecate WithMetricAttributesFn in favor of Labeler#8587pellared merged 6 commits intoopen-telemetry:mainfrom
pellared merged 6 commits intoopen-telemetry:mainfrom
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pellared
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Feb 27, 2026
dmathieu
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Mar 2, 2026
Co-authored-by: Robert Pająk <pellared@hotmail.com>
Co-authored-by: Robert Pająk <pellared@hotmail.com>
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@sonalgaud12, thank you! |
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Just bumped into this. A quick migration guide would be nice. I'm trying to figure it out... |
emcfarlane
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Mar 18, 2026
Add a `Labeler` type, a context-bound, mutex-protected attribute accumulator that handlers can use to attach custom metric attributes during request processing. Accessed via `LabelerFromContext` and `ContextWithLabeler`. This follows the same pattern as `otelhttp.Labeler` in the upstream OpenTelemetry contrib library, which deprecated `WithMetricAttributesFn` in favor of `Labeler` (open-telemetry/opentelemetry-go-contrib#8587). This implementation aligns with that decision and only adds the `Labeler` API. Attributes are added only to metrics, not to spans, since metric attributes directly affect time series cardinality and must be controlled independently from trace span attributes. Works for unary and streaming RPCs on both client and server. The interceptor injects a `Labeler` into the context automatically if one is not already present. Avoids allocations on the unary fast path when no custom attributes are set. Backward-compatible and additive, no existing APIs are modified. Motivation: standard RPC metrics (e.g. `rpc.server.duration`) already capture the right measurements but provide no way to attach custom dimensions (e.g. `product.variant`). `Labeler` solves this cleanly, matching the approach `otelhttp` uses for HTTP instrumentation. Closes #199. --------- Signed-off-by: Michal Jurecko <michal.jurecko@gmail.com>
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Addresses #8402
Related: #8107