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Workers user spans reach a tracing backend today only through Streaming Tail Workers: the Workers Observability tail worker rebuilds them in JavaScript from tail events. Spans built that way are cut off when a Durable Object hands off work, carry coarse I/O-clock timestamps, and are sampled only after they already exist. This gives the runtime what it needs to export user spans itself, as OTLP, the way other Cloudflare services already do: - an OTLP encoder for spans, written in Rust, behind the existing span submitter interface; - a tracer hook that lets the embedder open each invocation's root span, so the invocation and all of its user spans form one exported trace; - precise timestamps for user spans, which no longer reach user code directly. workerd can also export on its own: a new `tracing.otlp` setting sends each invocation's spans to an OTLP/HTTP collector such as a local Jaeger. That makes Workers traces visible in local development without a tail worker. Nothing changes unless an embedder installs the hook or the setting is configured. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The filter is a stopgap copied from the Workers Observability tail worker. Record why it is unsatisfying and that it can be removed once every binding talks to its backend over JSRPC. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Some bindings (D1, AI, Images, Vectorize) reach their backend with an internal fetch to a placeholder host. Those fetch spans were dropped when they ended, but by then their id had already been handed to the backend as its parent, so any spans the backend exported were orphaned at the top of the trace. Decide when the fetch starts instead: a fetch to one of these hosts opens no user span, and the binding's own span (such as d1_run) becomes the subrequest's parent. Matching by host is still a stopgap until every binding talks to its backend over JSRPC. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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jasnell
reviewed
Oct 11, 2026
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| // Where an OtlpSpanSubmitter's spans go, and which spans it takes. Refcounted because the | ||
| // submitters of one invocation share it and may outlive the tracer. | ||
| class OtlpSpanExporter: public kj::Refcounted { |
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nit: unless OtlpSpanExporter needs to hand off refs to itself, it really doesn't need to extend public kj::Refcounted any more right?
jasnell
reviewed
Oct 11, 2026
| @@ -7907,6 +7919,12 @@ kj::Promise<void> Server::startServices(jsg::V8System& v8System, | |||
| } | |||
| } | |||
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| if (config.getTracing().hasOtlp()) { | |||
| otlpExporter = kj::refcounted<OtlpExporter>( | |||
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kj::rc and kj::Rc instead?
jasnell
reviewed
Oct 11, 2026
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| class OtlpExporter; | ||
| // Set when the config's `tracing.otlp` names a collector. | ||
| kj::Maybe<kj::Own<OtlpExporter>> otlpExporter; |
jasnell
approved these changes
Oct 11, 2026
An uncaught exception reported for the invocation went only to the streaming tail, so the exported root span had the exception outcome but no exception event and no status message. Record it on the root, as tail-built traces did. An exception reported while one of the worker's own spans is active belongs to that span and is left off the root. When an exception supplies the status message, still derive error.type, so every ERROR span carries one. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Workers user spans reach a tracing backend today only through Streaming Tail Workers: the Workers Observability tail worker rebuilds them in JavaScript from tail events. Spans built that way are cut off when a Durable Object hands off work, carry coarse I/O-clock timestamps, and are sampled only after they already exist.
This gives the runtime what it needs to export user spans itself, as OTLP, the way other Cloudflare services already do:
workerd can also export on its own: a new
tracing.otlpsetting sends each invocation's spans to an OTLP/HTTP collector such as a local Jaeger. That makes Workers traces visible in local development without a tail worker.Nothing changes unless an embedder installs the hook or the setting is configured.