Known limitations
Workers tracing is currently in open beta. This page documents current limitations and any upcoming features on our roadmap.
To provide more feedback and send feature requests, head to the Workers tracing GitHub discussion ↗.
Due to security measures put in place to prevent Spectre attacks, the Workers
Runtime does not update time until I/O events take place. This means that some spans will return a length of 0 ms even when the operation took longer.
The Cloudflare Workers team is exploring security measures that would allow exposing time lengths at millisecond-level granularity in these cases.
When exporting traces to external platforms, trace IDs are not propagated. This means traces from your Workers won't link with traces from other services in your observability tools.
We're working on automatic trace context propagation using W3C Trace Context standards ↗, which will enable complete end-to-end visibility across your existing tools and services.
Calls to other Workers via service bindings or to Durable Objects create separate traces rather than nested spans. This means you'll see multiple independent traces in your dashboard instead of a single unified trace showing the full request flow.
We're working on connecting these traces automatically.
We are planning to add more detailed attributes on each span. You can find a complete list of what is already instrumented here.
Your feedback on any missing information will help us prioritize additions and changes. Please comment on the Workers tracing GitHub discussion ↗ if specific attributes would be helpful to use tracing effectively.
Automatic instrumentation covers many platform interactions, but we know you need visibility into your own application logic too. We're working to support the OpenTelemetry API ↗ to make it easier for you to instrument custom spans within your application.
As Workers tracing is currently in beta, span names and attribute names are not yet finalized. We may refine these names during the beta period to improve clarity and align with OpenTelemetry semantic conventions. We recommend reviewing the spans and attributes documentation periodically for updates.
- There are currently are a few attributes that only apply to some spans (e.g.
service.name,faas.name). When filtering or grouping by the Worker name across traces and logs, use$metadata.serviceinstead, as it will apply consistently across all event types. - While a trace is in progress, the event will show
Trace in Progresson the root span. Please wait a few moments for the full trace to become available