B3/Jaeger/OtTrace propagators not recognized — opentelemetry-extension-trace-propagators missing from opentelemetry-api classpath

[dudgns3443]

Summary

When otel.propagators=b3multi (or b3, jaeger, ottrace) is configured in the Jenkins OpenTelemetry plugin, Jenkins startup fails:

io.opentelemetry.sdk.autoconfigure.spi.ConfigurationException: Unrecognized value for otel.propagators: b3multi. Make sure the artifact including the propagator is on the classpath.
    at PluginClassLoader for opentelemetry-api//io.opentelemetry.sdk.autoconfigure.PropagatorConfiguration.getPropagator(PropagatorConfiguration.java:70)
    at PluginClassLoader for opentelemetry-api//io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdkBuilder.build(...)
    at PluginClassLoader for opentelemetry-api//io.jenkins.plugins.opentelemetry.api.ReconfigurableOpenTelemetry.configure(...)
    at PluginClassLoader for opentelemetry//io.jenkins.plugins.opentelemetry.JenkinsOpenTelemetryPluginConfiguration.configureOpenTelemetrySdk(...)

Root cause

opentelemetry-extension-trace-propagators is currently bundled in opentelemetry-plugin (compile scope), but the SDK autoconfigure (AutoConfiguredOpenTelemetrySdkBuilder.build()) which calls ServiceLoader<ConfigurablePropagatorProvider> runs in opentelemetry-api-plugin's classloader.

Because Jenkins plugin classloaders are isolated and the dependency direction is opentelemetry → opentelemetry-api (not the reverse), the SPI lookup in opentelemetry-api-plugin cannot see resources in opentelemetry-plugin/WEB-INF/lib/.

Verification on a running Jenkins

$JENKINS_HOME/plugins/opentelemetry-api/WEB-INF/lib/:

opentelemetry-sdk-extension-autoconfigure-1.49.0.jar  <- runs SPI lookup
(no opentelemetry-extension-trace-propagators)

$JENKINS_HOME/plugins/opentelemetry/WEB-INF/lib/:

opentelemetry-extension-trace-propagators-1.49.0.jar  <- contains B3/Jaeger/OtTrace SPI registrations

The JAR is on disk but on the wrong plugin's classpath, so ServiceLoader running in the SDK never sees the SPI provider files inside it.

History

• 2023-06: Add support for more trace propagators: Jaeger, Zipkin, OpenTracing, AWS X-Ray opentelemetry-plugin#668 ("Add support for more trace propagators: Jaeger, Zipkin, OpenTracing, AWS X-Ray") added opentelemetry-extension-trace-propagators to the (then-single) opentelemetry-plugin pom and resolved Make otel.propagators=jaeger possible opentelemetry-plugin#657. Released as opentelemetry-2.14.0.
• After the SDK was extracted into opentelemetry-api-plugin (mid-2025): the SDK + autoconfigure artifacts moved, but opentelemetry-extension-trace-propagators was left behind in opentelemetry-plugin. This is a silent regression — the dependency continues to exist but is no longer reachable by the SPI lookup, so all non-W3C propagators stop working.

Proposed fix

Add the dependency to opentelemetry-api-plugin/pom.xml, alongside opentelemetry-sdk-extension-autoconfigure:

<dependency>
    <groupId>io.opentelemetry</groupId>
    <artifactId>opentelemetry-extension-trace-propagators</artifactId>
</dependency>

This places the artifact (and its META-INF/services/io.opentelemetry.sdk.autoconfigure.spi.ConfigurablePropagatorProvider SPI file) on the same classloader as the SDK autoconfigure, restoring b3, b3multi, jaeger, and ottrace recognition.

The redundant declaration can also be removed from opentelemetry-plugin/pom.xml (separate PR), but adding it to opentelemetry-api-plugin is sufficient to fix the user-visible breakage.

Workaround until merged

Manual JAR copy on the Jenkins controller:

cp $JENKINS_HOME/plugins/opentelemetry/WEB-INF/lib/opentelemetry-extension-trace-propagators-1.49.0.jar \
   $JENKINS_HOME/plugins/opentelemetry-api/WEB-INF/lib/
# restart Jenkins

Replaced on every plugin upgrade.

Environment

• Jenkins OpenTelemetry plugin: 3.1505.v69c4d7c9ee62 (also reproducible on 3.1523.v0b_3ce640987d)
• opentelemetry-api plugin: 1.49.0.x
• OpenTelemetry SDK bundled: 1.49.0
• Jenkins core: 2.504.3
• Jenkins is unable to start with otel.propagators=b3multi set