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—you cannot just swap in the new code in-place.
<h3>Migration Steps</h3>
<ol>
<li>Setup a new cluster running 0.8.
<li>Use the 0.7 to 0.8 <ahref="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.