Paul Millar created ZOOKEEPER-2812:
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Summary: Racy implicit SessionTracker creation
Key: ZOOKEEPER-2812
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2812
Project: ZooKeeper
Issue Type: Bug
Components: server
Affects Versions: 3.4.8
Reporter: Paul Millar
Priority: Minor
As with ZOOKEEPER-2810, NIOServerCnxnFactory#startup current starts the
acceptor thread before initialising the ZooKeeperServer object. This leads to
a race-condition between any incoming connection and the thread initialising
the ZooKeeperServer.
If the incoming connection wins the race then the thread processing this
connection will see an uninitialised SessionTracker object, resulting in the
following NPE being thrown:
{noformat}
java.lang.NullPointerException: null
at
org.apache.zookeeper.server.ZooKeeperServer.createSession(ZooKeeperServer.java:569)
~[zookeeper-3.4.8.jar:3.4.8--1]
at
org.apache.zookeeper.server.ZooKeeperServer.processConnectRequest(ZooKeeperServer.java:902)
~[zookeeper-3.4.8.jar:3.4.8--1]
at
org.apache.zookeeper.server.NIOServerCnxn.readConnectRequest(NIOServerCnxn.java:418)
~[zookeeper-3.4.8.jar:3.4.8--1]
at
org.apache.zookeeper.server.NIOServerCnxn.readPayload(NIOServerCnxn.java:198)
~[zookeeper-3.4.8.jar:3.4.8--1]
at
org.apache.zookeeper.server.NIOServerCnxn.doIO(NIOServerCnxn.java:244)
~[zookeeper-3.4.8.jar:3.4.8--1]
at
org.apache.zookeeper.server.NIOServerCnxnFactory.run(NIOServerCnxnFactory.java:203)
~[zookeeper-3.4.8.jar:3.4.8--1]
{noformat}
Again, as with ZOOKEEPER-2810, the naive fix (starting the acceptor thread last
in NIOServerCnxnFactory#startup method) may fix this issue.
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