He-Pin opened a new issue, #3231:
URL: https://github.com/apache/pekko/issues/3231
### Motivation
The typed actor logging documentation explicitly states that `sourceThread`
should be available in MDC, but the implementation does not set this value.
This creates a documentation/implementation mismatch that affects users who
rely on the documented behavior to identify which thread an actor was running
on when logging.
### Current behavior
In
`actor-typed/src/main/scala/org/apache/pekko/actor/typed/internal/ActorMdc.scala:29-38`,
the `setMdc` method only sets four MDC values:
- `pekkoSource`
- `sourceActorSystem`
- `pekkoAddress`
- `pekkoTags` (conditional)
The `sourceThread` MDC value is never set, despite being documented.
### Expected behavior
The `setMdc` method should also set `sourceThread` with
`Thread.currentThread().getName`, matching the behavior of the classic
`Slf4jLogger` which sets this value at
`slf4j/src/main/scala/org/apache/pekko/event/slf4j/Slf4jLogger.scala:134`.
The documentation at `docs/src/main/paradox/typed/logging.md:412-413` states:
> "Since the logging is done asynchronously, the thread in which the logging
was performed is captured in MDC with attribute name `sourceThread`."
### Code evidence
**Missing implementation:**
-
`actor-typed/src/main/scala/org/apache/pekko/actor/typed/internal/ActorMdc.scala:29-38`
- `setMdc` does not set `sourceThread`
**Working reference (classic logger):**
- `slf4j/src/main/scala/org/apache/pekko/event/slf4j/Slf4jLogger.scala:134`
- `MDC.put(mdcThreadAttributeName, logEvent.thread.getName)`
**Documentation promise:**
- `docs/src/main/paradox/typed/logging.md:412-413` - explicitly states
`sourceThread` is available
**Missing test coverage:**
-
`actor-typed-tests/src/test/scala/org/apache/pekko/actor/typed/scaladsl/ActorLoggingSpec.scala:500-506`
- `assertExpectedMdc` only checks for `pekkoAddress`, `pekkoSource`, and
`sourceActorSystem`, not `sourceThread`
### Reproduction
1. Create a typed actor that logs a message
2. Configure logback to include `%X{sourceThread}` in the pattern
3. Observe that `sourceThread` is empty/missing in the log output
4. Compare with a classic actor where `sourceThread` is correctly populated
Example test case:
```scala
Behaviors.setup[String] { context =>
context.log.info("test")
val thread = MDC.get("sourceThread")
// Expected: thread should be non-null and contain the actor's thread name
// Actual: thread is null
Behaviors.empty
}
```
### Impact
- **Module:** pekko-actor-typed
- **Affected users:** All users of typed actors who rely on MDC for
structured logging and expect `sourceThread` to be available as documented
- **Use cases affected:** Log analysis, debugging, and monitoring that
depend on knowing which thread an actor was executing on when logging
- **Consistency:** Creates inconsistency between classic and typed actor
logging behavior
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