feat(CLDSRV-884): Add OpenTelemetry tracing instrumentation #6140
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,92 @@ | ||
| 'use strict'; | ||
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| const tracing = require('../tracing'); | ||
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| let tracer = null; | ||
| function getTracer() { | ||
| if (tracer) { | ||
| return tracer; | ||
| } | ||
| const { trace } = require('@opentelemetry/api'); | ||
| const { version } = require('../../package.json'); | ||
| tracer = trace.getTracer('cloudserver-api', version); | ||
| return tracer; | ||
| } | ||
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| async function endSpanWhenSettled(promise, endSpan) { | ||
| try { | ||
| const value = await promise; | ||
| endSpan(); | ||
| return value; | ||
| } catch (err) { | ||
| endSpan(err); | ||
| throw err; | ||
| } | ||
| } | ||
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| function instrumentApiMethod(apiMethod, methodName) { | ||
| if (!tracing.isEnabled()) { | ||
| return apiMethod; | ||
| } | ||
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| const api = require('@opentelemetry/api'); | ||
| const spanName = `api.${methodName}`; | ||
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| return function instrumented(...args) { | ||
| const callbackIndex = args.findLastIndex(a => typeof a === 'function'); | ||
| const span = getTracer().startSpan(spanName, { kind: api.SpanKind.INTERNAL }); | ||
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| // End-once guard. Multiple termination paths can race: the | ||
| // wrapped callback may fire and then the handler may also throw | ||
| // synchronously, or a callback-and-Promise hybrid handler may | ||
| // resolve after firing the callback. | ||
| let spanEnded = false; | ||
| const endSpan = err => { | ||
| if (spanEnded) { | ||
| return; | ||
| } | ||
| spanEnded = true; | ||
| if (err) { | ||
| span.recordException(err); | ||
| span.setStatus({ code: api.SpanStatusCode.ERROR }); | ||
| if (err.code) { | ||
| span.setAttribute('cloudserver.error_code', err.code); | ||
| } | ||
| } else { | ||
| span.setStatus({ code: api.SpanStatusCode.OK }); | ||
| } | ||
| span.end(); | ||
| }; | ||
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| const wrappedArgs = [...args]; | ||
| if (callbackIndex !== -1) { | ||
| const originalCallback = args[callbackIndex]; | ||
| wrappedArgs[callbackIndex] = function wrappedCallback(err, ...results) { | ||
| endSpan(err); | ||
| return originalCallback.call(this, err, ...results); | ||
| }; | ||
| } | ||
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| const ctx = api.trace.setSpan(api.context.active(), span); | ||
| try { | ||
| const result = api.context.with(ctx, () => apiMethod.apply(this, wrappedArgs)); | ||
| if (callbackIndex === -1) { | ||
| if (result && typeof result.then === 'function') { | ||
| return endSpanWhenSettled(result, endSpan); | ||
| } | ||
| endSpan(); | ||
| } | ||
| // Callback-style handler: the wrapped callback drives the | ||
| // span lifecycle. If the handler also returns a thenable | ||
| // (hybrid migration shape), pass it through untouched — | ||
| // attaching a second .then() chain would surface as an | ||
| // unhandled rejection in callback-only callers. | ||
| return result; | ||
| } catch (error) { | ||
|
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| endSpan(error); | ||
| throw error; | ||
| } | ||
| }; | ||
| } | ||
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| module.exports = { instrumentApiMethod }; | ||
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Contributor
There was a problem hiding this comment. Are we use about that ? We usually trace them as they can have an impact (as you said high-frequency). The filter is not done here but in the tool used to explore trace ?
Contributor
Author
There was a problem hiding this comment. Both options exist; we deliberately filter at ingest. Three reasons:
The filter is |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,18 @@ | ||
| 'use strict'; | ||
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| // Probe + scrape paths that should never produce a span. Filtered at | ||
| // ingest (not at the trace backend) because probe rate × pod count × | ||
| // always-on sampling overwhelms the exporter and storage with traffic | ||
| // nobody queries. | ||
| const HEALTH_PATHS = new Set(['/live', '/ready', '/_/healthcheck', '/_/healthcheck/deep', '/metrics']); | ||
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| function isHealthPath(url) { | ||
| if (typeof url !== 'string' || url.length === 0) { | ||
| return false; | ||
| } | ||
| const qIdx = url.indexOf('?'); | ||
| const path = qIdx === -1 ? url : url.slice(0, qIdx); | ||
| return HEALTH_PATHS.has(path); | ||
| } | ||
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| module.exports = { isHealthPath }; |
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But then we will not have the following trace if we have a double-ending ? Why did you introduce what ? Did you encounter that ? If we remove that, what is the impact ?
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Yes — encountered during initial unit-test development. The case: a callback-style handler fires the callback (which ends the span via the wrapped-callback closure) and then throws synchronously afterwards (e.g. the callback body itself threw). The outer
try/catchthen callsendSpan(err)and we get two.end()calls. OTEL warns on double-end and the second status overwrites the first, so the trace would record ERROR when the operation actually succeeded. The guard makes the first ending win. Theends span exactly once when callback fires then handler throwstest ininstrumentationSimple.spec.jsexercises exactly this path.