Zipkin reporter "failed to report spans" on port 9411 in CI

By Daniel Zoghalchali·Latchkey

A Zipkin reporter posts encoded spans to http://localhost:9411/api/v2/spans. When no Zipkin server runs in CI, the connection is refused; depending on the client, spans are dropped or the reporter logs an error each flush.

What this error means

Logs show "Dropped ... spans" or "failed to report" / "connection refused" against :9411/api/v2/spans while the test suite runs.

Reporting spans to Zipkin failed:
POST http://localhost:9411/api/v2/spans failed:
connect ECONNREFUSED 127.0.0.1:9411

Common causes

No Zipkin server on 9411 in CI

The reporter targets the default Zipkin collector endpoint on port 9411. Without a Zipkin service, POSTs are refused and spans are dropped.

Reporter created unconditionally in tests

The tracer initializes a Zipkin HTTP reporter regardless of environment, so importing the app under test starts trying to report.

How to fix it

Skip the Zipkin reporter in tests

1. Use a no-op / in-memory reporter when running tests.
2. If reporting must be exercised, run the Zipkin server as a service.
3. Point the reporter endpoint at that service, not a remote host.

services:
  zipkin:
    image: openzipkin/zipkin:latest
    ports: ['9411:9411']

Assert on spans in memory

Collect spans with an in-memory handler and assert on them rather than posting to a live server.

How to prevent it

• Disable the Zipkin reporter for unit tests.
• Run openzipkin/zipkin as a service only when export is under test.
• Do not point CI reporters at remote Zipkin hosts.

Frequently asked questions

Related guides

References

• GitHub Actions documentation