how to propagate trace id for fetch instrumentation to backend services

[krishnaexplore]

how to propagate trace id for fetch instrumentation to backend services

propagateTraceHeaderCorsUrls: [new RegExp('https://env1.example.co/*')],. this is not working , but in local it is working

propagateTraceHeaderCorsUrls: [new RegExp('http://localhost:8080/*')],

[sayedrisat]

The * in a JavaScript regular expression repeats only the character immediately before it. So new RegExp('https://env1.example.co/*') means “the literal prefix https://env1.example.co/, followed by zero or more / characters”; it does not mean “any path”. The dots are also wildcards unless escaped.

Try an anchored regex for that origin, for example:

propagateTraceHeaderCorsUrls: [/^https:\/\/env1\.example\.co(?:\/|$)/],

Also make sure the API’s CORS response allows the injected request headers (traceparent, and potentially tracestate/baggage, depending on the configured propagator). A cross-origin fetch can otherwise fail its preflight even when the client instrumentation is configured to inject headers. propagateTraceHeaderCorsUrls controls whether fetch instrumentation injects trace headers for that URL: https://github.com/open-telemetry/opentelemetry-js/blob/main/experimental/packages/opentelemetry-instrumentation-fetch/src/fetch.ts.