feat: inject traceparent meta tag when OpenTelemetry is active#3729
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When an OTel exporter is configured, Fresh now automatically adds a
<meta name="traceparent"> tag to the <head> of rendered HTML pages.
This enables client-side OTel instrumentation (e.g.,
@opentelemetry/instrumentation-document-load) to connect browser
traces to the server-side span that rendered the page.
The tag follows the W3C Trace Context format:
<meta name="traceparent" content="00-{traceId}-{spanId}-{flags}">
Only injected when a valid span context exists (real OTel exporter
configured), so there is zero overhead when OTel is not in use.
Closes #2830
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Move `as any` cast to a single line so the deno-lint-ignore directive covers it, fixing ban-unused-ignore and no-explicit-any errors on CI. Also document the new traceparent meta tag injection in the OpenTelemetry docs page. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The ignore directive only applies to the immediately following line. After formatting, `items.push(` was on its own line, so the directive covered that instead of the `as any` cast. Move the comment inside the push() call, directly above the line that needs it. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
npmjs.com returns 403 to automated link checkers. Link to the OpenTelemetry GitHub repo instead. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The package is under packages/, not plugins/web/. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
When an OpenTelemetry exporter is configured, Fresh now automatically injects a
<meta name="traceparent">tag into the<head>of rendered HTML pages. This enables client-side OTel instrumentation (e.g.,@opentelemetry/instrumentation-document-load) to connect browser performance traces to the server-side span that rendered the page.Output example
How it works
<head>rendering inpreact_hooks.ts, checks for an active OTel span viatrace.getActiveSpan()isSpanContextValid()to ensure a real exporter is configured (not the no-op default)<meta name="traceparent">tag in W3C Trace Context format:00-{traceId}-{spanId}-{traceFlags}getActiveSpan()returnsundefinedwith the no-op providerTest plan
deno test -A packages/fresh/src/app_test.tsx— 46 passeddeno test -A packages/fresh/src/fs_routes_test.tsx— 55 passedCloses #2830
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