kafka/docs/migration.html

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<h2><a id="migration" href="#migration">Migrating from 0.7.x to 0.8</a></h2>

0.8 is our first (and hopefully last) release with a non-backwards-compatible wire protocol, ZooKeeper     layout, and on-disk data format. This was a chance for us to clean up a lot of cruft and start fresh. This means performing a no-downtime upgrade is more painful than normal&mdash;you cannot just swap in the new code in-place.

<h3><a id="migration_steps" href="#migration_steps">Migration Steps</a></h3>

<ol>
    <li>Setup a new cluster running 0.8.
    <li>Use the 0.7 to 0.8 <a href="tools.html">migration tool</a> to mirror data from the 0.7 cluster into the 0.8 cluster.
    <li>When the 0.8 cluster is fully caught up, redeploy all data <i>consumers</i> running the 0.8 client and reading from the 0.8 cluster.
    <li>Finally migrate all 0.7 producers to 0.8 client publishing data to the 0.8 cluster.
    <li>Decommission the 0.7 cluster.
    <li>Drink.
</ol>

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