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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ACCUMULO-2743) Improve stale-reads with ZooKeeper-backed data
Date Mon, 28 Apr 2014 17:40:15 GMT
Josh Elser created ACCUMULO-2743:
------------------------------------

             Summary: Improve stale-reads with ZooKeeper-backed data
                 Key: ACCUMULO-2743
                 URL: https://issues.apache.org/jira/browse/ACCUMULO-2743
             Project: Accumulo
          Issue Type: Improvement
            Reporter: Josh Elser
             Fix For: 1.7.0


Writing test code against Accumulo, especially via MiniAccumuloCluster, can be extremely frustrating.
ZooKeeper is used for managing table configurations, among other things, to allow all tabletservers
to be aware of the state of a table.

The problem is that each tabletserver uses a Watcher to see when updates occur, and then it
updates an internal cache of these properties. This is a problem even on an instance with
a single tserver when setting a table property (configuring an iterator is a good example).
The setTableProperty command is implemented via the Master, not a tserver like fetching the
table configuration is implemented, which means that you're racing against the Watcher in
the tserver.

The cause of this is that test code gets riddled with code like the following:

{code}
String myProperty = tableConfiguration.getProperty("myProperty");
for (int i = 0; i < retries && null == myProperty; i++) {
  myProperty = tableConfiguration.getProperty("myProperty");
  Thread.sleep(some_millis);
}
// Hope that you actually saw the update
Assert.assertNotNull(myProperty)
{code}



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