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xytan0056
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Jul 7, 2026
| - shared metric-name, op-name, and tag-key constants | ||
| - default histogram buckets sized for RPC latency and large target counts | ||
| - an in-flight gauge helper that owns the atomic counter callers otherwise reinvent | ||
| - a failure classifier that reuses the errors package |
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@justinwon777 place holder for errors package design RFC
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Ports the Tango Metrics Inventory RFC into the repo. Covers the Emitter contract, buckets, TrackInFlight, RecordFailure, context propagation, shared constants, and OSS / internal / CLI usage.
sywhang
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Jul 8, 2026
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| ## Emitter | ||
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| `Emitter` is an interface. `New(scope)` returns the default tally-backed implementation; `New(nil)` returns one backed by `tally.NoopScope` so callers do not need to special-case unwired metrics. This also serves as a noop fallback. |
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| `Emitter` is an interface. `New(scope)` returns the default tally-backed implementation; `New(nil)` returns one backed by `tally.NoopScope` so callers do not need to special-case unwired metrics. This also serves as a noop fallback. | |
| `Emitter` is an interface. `New(scope)` returns the default tally-backed implementation; `New(nil)` returns one backed by `tally.NoopScope` so callers do not need to special-case metrics using alternative metrics library than tally. This also serves as a no-op fallback which could be useful for things like tests. |
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| `New(scope)` returns the default tally-backed implementation; `New(nil)` returns one backed by `tally.NoopScope` so callers do not need to special-case unwired metrics. | ||
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| `Tagged` returns a child Emitter that adds tags to every subsequent emission. The parent is unchanged. The child shares the in-flight counter map, so a `TrackInFlight` increment on a parent and its decrement on a tagged child balance to zero. | ||
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| Options are variadic and compose. `WithTags` merges into the base tag set with later-wins semantics on key collision. `WithDurationBuckets` / `WithValueBuckets` override the emitter's default histogram buckets on a single call. |
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can this section be written as a docstring with func signature?
// New returns the default Tally-backed Emitter implementation.
func New(scope tally.Scope) Emitter
// and so on... |
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| Options are variadic and compose. `WithTags` merges into the base tag set with later-wins semantics on key collision. `WithDurationBuckets` / `WithValueBuckets` override the emitter's default histogram buckets on a single call. | ||
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| ## Op-as-subscope |
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| Every emit call takes an op name as its first argument. `e.Inc("get_target_graph", "requests")` emits under `<scope>.get_target_graph.requests`. Consumers that own their own ops (an extension RPC, a background job) should declare `const opXYZ = "xyz"` next to the emit site rather than adding to `names.go`. | ||
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| ## TrackInFlight |
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same thing here, let's make this into an API form.
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| Every RPC calls one of: | ||
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| - `e.Inc(op, Requests, WithTags({result: success}))` on the happy path |
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Inc and RecordFailure aren't intuitive names for counterparts of each other. can we rename?
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Also, not sure why is Inc and failure/success is a thing. Do we need this?
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| ## Constants | ||
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| All shared constants live in `names.go`: operation names (`OpGetTargetGraph`, `OpGetChangedTargets`, ...), metric names (`Requests`, `TotalDuration`, `InFlightRequests`, ...), tag keys (`TagRepo`, `TagEmitter`, `TagResult`, `TagFailureType`, `TagFailureSource`, ...), and `Result*` values (`ResultSuccess`, `ResultFail`, `ResultHit`, `ResultMiss`). |
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where they live isn't relevant to this RFC.
Can we make this into a table form?
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add Tango Metrics Inventory RFC into the repo. Covers the Emitter contract, metrics invetnory, context propagation design and other utils and their usage.