Add an invariants section to the developer docs; added the one about no permanent data in zk

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1381740 13f79535-47bb-0310-9956-ffa450edef68
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Michael Stack 2012-09-06 20:16:48 +00:00
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commit e0d8aea624
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@ -626,6 +626,21 @@ mvn compile
<para>This convention comes from our parent project Hadoop.</para>
</section> <!-- code.standards -->
<section xml:id="design.invariants">
<title>Invariants</title>
<para>We don't have many but what we have we list below. All are subject to challenge of
course but until then, please hold to the rules of the road.
</para>
<section xml:id="design.invariants.zk.data">
<title>No permanent state in ZooKeeper</title>
<para>ZooKeeper state should transient (treat it like memory). If deleted, hbase
should be able to recover and essentially be in the same state<footnote><para>There are currently
a few exceptions that we need to fix around whether a table is enabled or disabled</para></footnote>.
</para>
</section>
</section> <!-- design.invariants -->
<section xml:id="run.insitu">
<title>Running In-Situ</title>
<para>If you are developing HBase, frequently it is useful to test your changes against a more-real cluster than what you find in unit tests. In this case, HBase can be run directly from the source in local-mode.