Github user mikaelstaldal commented on the issue:
https://github.com/apache/logging-log4j2/pull/112
It would also be useful to enable interpolation with
[lookups](https://logging.apache.org/log4j/2.x/manual/lookups.html) for the
key, so that you could e.g. use some value from the thread context:
```
<Kafka name="Kafka" topic="log-test" key="$${ctx:key}">
```
See e.g.
[here](https://github.com/apache/logging-log4j2/blob/master/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/HttpURLConnectionManager.java#L95)
about how to do that.
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