jinrongluo commented on issue #386:
URL:
https://github.com/apache/incubator-eventmesh/issues/386#issuecomment-860735664
Root Cause Analysis:
After studying EventMesh code and debug logs, I found out a racing condition
and class variable sharing issue in eventmesh-connector-rocketmq module.
In `org.apache.eventmesh.connector.rocketmq.consumer.PushConsumerImpl.java`
Every new message being consumed, it will set the message's context into
`PushConsumerImpl.context` variable
https://github.com/apache/incubator-eventmesh/blob/develop/eventmesh-connector-rocketmq/src/main/java/org/apache/eventmesh/connector/rocketmq/consumer/PushConsumerImpl.java#L134-L136
This context is pass through different layers of consumer handlers, and
finally used in
`org.apache.rocketmq.client.impl.consumer.ConsumeMessageConcurrentlyService.java`
to update the Queue Consumer Offset back to RocketMQ
https://github.com/apache/incubator-eventmesh/blob/develop/eventmesh-connector-rocketmq/src/main/java/org/apache/rocketmq/client/impl/consumer/ConsumeMessageConcurrentlyService.java#L352-L364
However, I found that `PushConsumerImpl.context` variable is being shared by
multiple thread in EventMeshMessageListenerConcurrently object when registered
into DefaultMQPushConsumer.
So every new message will update PushConsumerImpl.context of itself, and the
old message's context is overridden. So the old message is not able to update
its Queue Consumer Offset using its own context.
We should not let all messages to share the same PushConsumerImpl.context
class variable. We should have each message to maintain its own context and
passing through the consumer handlers, without being modified.
I will propose a fix based on this analysis.
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