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https://issues.apache.org/jira/browse/KAFKA-2510?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14731497#comment-14731497
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Jay Kreps commented on KAFKA-2510:
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I actually think we shouldn't prevent this.
In our replication model the data on disk is basically a cache. If it's there
the broker uses it to help make its own recovery faster and just pulls the diff
from replicas. If its not there it recreates it. You are allowed to lose what
is on disk at any time.
For the chef case, yes, if you botch the directory you will replicate data, but
the same is true of the old node id as well as things like the zk URL, etc.
Replicating will be slow but not fatal. The case of rolling restart is not
correct if you use controlled shutdown. If you don't use controlled shutdown
you will lose data no matter what.
So today if you want you can wipe your data and restart and the broker happily
re-replicates. If you have a disk failure you can repair it and restart. And if
your AWS instance disappears you can move it over to another and it
re-replicates.
We actually intended to exploit this for running in AWS and Mesos more
elastically when we do automated data balancing. For example in Mesos the mesos
guys are going to add a feature in Marathon where tasks will be semi-sticky to
nodes. So if a Kafka node is restarted or dies mesos will prefer to restart it
on the node it was on (if that node is still around and has free slots). If not
it will start it elsewhere (where it will, of course, have no data).
> Prevent broker from re-replicating / losing data due to disk misconfiguration
> -----------------------------------------------------------------------------
>
> Key: KAFKA-2510
> URL: https://issues.apache.org/jira/browse/KAFKA-2510
> Project: Kafka
> Issue Type: Bug
> Reporter: Gwen Shapira
>
> Currently Kafka assumes that whatever it sees in the data directory is the
> correct state of the data.
> This means that if an admin mistakenly configures Chef to use wrong data
> directory, one of the following can happen:
> 1. The broker will replicate a bunch of partitions and take over the network
> 2. If you did this to enough brokers, you can lose entire topics and
> partitions.
> We have information about existing topics, partitions and their ISR in
> zookeeper.
> We need a mode in which if a broker starts, is in ISR for a partition and
> doesn't have any data or directory for the partition, the broker will issue a
> huge ERROR in the log and refuse to do anything for the partition.
> [~fpj] worked on the problem for ZK and had some ideas on what is required
> here.
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