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https://issues.apache.org/jira/browse/KAFKA-1835?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14625234#comment-14625234
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Jiangjie Qin commented on KAFKA-1835:
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[~guozhang][~jkreps] What do you think on this? The scenario we want to solve
is user don't want to send to be blocked in anyway. Assuming KIP-19 is done,
user will set max.block.ms to be 0. In that case, the problem becomes how can
the first send() get through.
I am thinking maybe we can do a metadata refresh when the clients get
instantiated. There might be some overhead because this will get the metadata
of all the topic back, but I don't think this will be a big issue. Any thoughts?
> Kafka new producer needs options to make blocking behavior explicit
> -------------------------------------------------------------------
>
> Key: KAFKA-1835
> URL: https://issues.apache.org/jira/browse/KAFKA-1835
> Project: Kafka
> Issue Type: Improvement
> Components: clients
> Affects Versions: 0.8.2.0, 0.8.3, 0.9.0
> Reporter: Paul Pearcy
> Fix For: 0.8.3
>
> Attachments: KAFKA-1835-New-producer--blocking_v0.patch,
> KAFKA-1835.patch
>
> Original Estimate: 504h
> Remaining Estimate: 504h
>
> The new (0.8.2 standalone) producer will block the first time it attempts to
> retrieve metadata for a topic. This is not the desired behavior in some use
> cases where async non-blocking guarantees are required and message loss is
> acceptable in known cases. Also, most developers will assume an API that
> returns a future is safe to call in a critical request path.
> Discussing on the mailing list, the most viable option is to have the
> following settings:
> pre.initialize.topics=x,y,z
> pre.initialize.timeout=x
>
> This moves potential blocking to the init of the producer and outside of some
> random request. The potential will still exist for blocking in a corner case
> where connectivity with Kafka is lost and a topic not included in pre-init
> has a message sent for the first time.
> There is the question of what to do when initialization fails. There are a
> couple of options that I'd like available:
> - Fail creation of the client
> - Fail all sends until the meta is available
> Open to input on how the above option should be expressed.
> It is also worth noting more nuanced solutions exist that could work without
> the extra settings, they just end up having extra complications and at the
> end of the day not adding much value. For instance, the producer could accept
> and queue messages(note: more complicated than I am making it sound due to
> storing all accepted messages in pre-partitioned compact binary form), but
> you're still going to be forced to choose to either start blocking or
> dropping messages at some point.
> I have some test cases I am going to port over to the Kafka producer
> integration ones and start from there. My current impl is in scala, but
> porting to Java shouldn't be a big deal (was using a promise to track init
> status, but will likely need to make that an atomic bool).
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