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https://issues.apache.org/jira/browse/KAFKA-2042?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14378954#comment-14378954
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Jun Rao commented on KAFKA-2042:
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Could you explain a bit more when the new producer will send a TMR with an
empty topic list? I can see this happen if after the producer is created, no
message is sent within the window of metadata age. Is that the only case when
this can happen?
> New producer metadata update always get all topics.
> ---------------------------------------------------
>
> Key: KAFKA-2042
> URL: https://issues.apache.org/jira/browse/KAFKA-2042
> Project: Kafka
> Issue Type: Bug
> Reporter: Jiangjie Qin
> Assignee: Jiangjie Qin
> Priority: Blocker
> Fix For: 0.8.3
>
> Attachments: KAFKA-2042.patch, KAFKA-2042_2015-03-24_13:37:49.patch,
> KAFKA-2042_2015-03-24_13:57:23.patch
>
>
> The new java producer metadata.topics is initially empty so the producer
> sends TMR with empty topic set. The broker takes the empty requested topic
> set as all topics, so metadata.cluster contains all topic metadata. Later on,
> when a new topic was produced, it gets added into the metadata.topics. The
> next metadata update will only contain the meta data for this new topic, so
> the metadata.cluster will only have this topic. Since there are a lot of
> messages are still in the accumulator but has no metadata in
> metadata.cluster, if a caller thread do a flush(), the caller thread will
> block forever because the messages sitting in accumulator without metadata
> will never be ready to send.
> We should add check for the metadata.topics, if it is empty, no TMR should be
> sent.
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