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context.Done() may never reach if waiting on r.incoming <- msgErr #936

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merged 1 commit into from
Sep 13, 2023
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context.Done() may never reach if waiting on r.incoming <- msgErr #936

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12 changes: 10 additions & 2 deletions protocol/kafka_sarama/v2/receiver.go
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Original file line number Diff line number Diff line change
Expand Up @@ -66,15 +66,23 @@ func (r *Receiver) ConsumeClaim(session sarama.ConsumerGroupSession, claim saram
return nil
}
m := NewMessageFromConsumerMessage(msg)

r.incoming <- msgErr{
msgErrObj := msgErr{
msg: binding.WithFinish(m, func(err error) {
if protocol.IsACK(err) {
session.MarkMessage(msg, "")
}
}),
}

// Need to use select clause here, otherwise r.incoming <- msgErrObj can become a blocking operation,
// resulting in never reaching outside block's case <-session.Context().Done()
select {
case r.incoming <- msgErrObj:
// do nothing
case <-session.Context().Done():
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spot on! usually we'd return session.Context.Err() to let the caller know why the function returned. But this would break the existing behavior (returning nil). A user could always use context.Cause(ctx), but that might not be intuitive from the nil behavior.

Anyways, IMHO with this change you can remove the code in line 95?

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Code on line 95 is still required. If code on line no. 64 case msg, ok := <-claim.Messages(): doesn't get hit, that code on line no. 95 would exit the flow.

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True, was under the assumption that ok would be false due to propagated channel somewhere into Sarama...but seems that's not the case.

return nil
}

// Should return when `session.Context()` is done.
// If not, will raise `ErrRebalanceInProgress` or `read tcp <ip>:<port>: i/o timeout` when kafka rebalance. see:
// https://github.com/Shopify/sarama/issues/1192
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