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From David Newberger <david.newber...@wandcorp.com>
Subject RE: Kafka Beginners planning problem.
Date Tue, 05 Jul 2016 15:24:56 GMT

I think the recommended approach to this would be to have a single topic and partition it
by userId. This will give you locality and order by user. If you think about it this would
give you a better ordering guarantee than if you had one topic per users. It's also a lot
more efficient. If you are using Kafka as a log or messaging system you really should not
need millions of topics or partitions. If I'm miss understanding the use case please let me


David Newberger

-----Original Message-----
From: Hyounmin Wang [mailto:hyunmin90@gmail.com] 
Sent: Tuesday, July 5, 2016 1:50 AM
To: users@kafka.apache.org
Subject: Kafka Beginners planning problem.

Hi there!

I'm new grad engineer and is pretty new to kafka world.

I'm trying to replace rabbit mq with apache-kafka and while planning, I bumped in to several
conceptual planning problem.

First we are using rabbit mq for per user queue policy meaning each user uses one queue. This
suits our need because each user represent some job to be done with that particular user,
and if that user causes a problem, the queue will never have a problem with other users because
queues are seperated ( Problem meaning messages in the queue will be dispatch to the users
using http request. If user refuses to receive a message (server down
perhaps?) it will go back in retry queue, which will result in no loses of message (Unless
queue goes down))

Now kafka is fault tolerant and failure safe because it write to a disk.
And its exactly why I am trying to implement kafka to our structure.

but there are problem to my plannings.

First, I was thinking to create as many topic as per user meaning each user would have each
topic (What problem will this cause? My max estimate is that I will have around 1~5 million

Second, If I decide to go for topics based on operation and partition by random hash of users
id, if there was a problem with one user not consuming message currently, will the all user
in the partition have to wait ? What would be the best way to structure this situation?

So as conclusion, 1~5 millions users. We do not want to have one user blocking large number
of other users being processed. Having topic per user will solve this issue, it seems like
there might be an issue with zookeeper if such large number gets in (Is this true? )

what would be the best solution for structuring? Considering scalability?
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