Erik van Oosten created KAFKA-14972:
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Summary: Make KafkaConsumer usable in async runtimes
Key: KAFKA-14972
URL: https://issues.apache.org/jira/browse/KAFKA-14972
Project: Kafka
Issue Type: Wish
Components: consumer
Reporter: Erik van Oosten
KafkaConsumer contains a check that rejects nested invocations from different
threads (method {{{}acquire{}}}). For users that use an async runtime, this is
an almost impossible requirement. Examples of async runtimes that are affected
are Kotlin co-routines (see KAFKA-7143) and Zio.
We propose to replace the thread-id check with an access-id that is stored on a
thread-local variable. Existing programs will not be affected. Developers that
work in an async runtime can pick up the access-id and set it on the
thread-local variable in a thread of their choosing.
Every time a callback is invoked a new access-id is generated. When the
callback completes, the previous access-id is restored.
This proposal does not make it impossible to use the client incorrectly.
However, we think it strikes a good balance between making correct usage from
an async runtime possible while making incorrect usage difficult.
Alternatives considered:
# Configuration that switches off the check completely.
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