Chris Egerton created KAFKA-14858:
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Summary: Standalone herder does not handle exceptions thrown from
connector taskConfigs method
Key: KAFKA-14858
URL: https://issues.apache.org/jira/browse/KAFKA-14858
Project: Kafka
Issue Type: Bug
Components: KafkaConnect
Reporter: Chris Egerton
In distributed mode, if a connector throws an exception from its
{{taskConfigs}} method (invoked by the herder, through the {{Worker}} class,
[here|https://github.com/apache/kafka/blob/f3e4dd922933bf28b2c091e846cbc4e5255dd1d5/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/distributed/DistributedHerder.java#L1960]),
we wait for an exponential backoff period (see KAFKA-14732) and then [retry
the
operation|https://github.com/apache/kafka/blob/f3e4dd922933bf28b2c091e846cbc4e5255dd1d5/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/distributed/DistributedHerder.java#L1907-L1911].
However, in standalone mode, not only do we not retry the operation, we do not
even log the exception. In addition, when REST calls are made that require
generating new task configs for a connector (which include creating and
reconfiguring a connector), if the connector's {{taskConfigs}} method throws an
exception, those requests will time out since the
[callback|https://github.com/apache/kafka/blob/f3e4dd922933bf28b2c091e846cbc4e5255dd1d5/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/standalone/StandaloneHerder.java#L183]
we use to respond to those requests never gets invoked.
At a bare minimum, we should:
* Log any exceptions thrown from the {{taskConfigs}} method at {{ERROR}} level
* Invoke any callbacks passed in to the relevant {{StandaloneHerder}} methods
with any exceptions thrown by the {{taskConfigs}} method
We might also consider introducing the same kind of exponential backoff retry
logic used by distributed mode, but this can be addressed separately since it
would be a much larger change in behavior and may break existing user's
deployments.
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