Hari Krishna Dara created ZOOKEEPER-2667:
--------------------------------------------
Summary: NPE in the patch for ZOOKEEPER-2139 when multiple
connections are made
Key: ZOOKEEPER-2667
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2667
Project: ZooKeeper
Issue Type: Bug
Components: java client
Affects Versions: 3.5.2, 3.6.0
Reporter: Hari Krishna Dara
ZOOKEEPER-2139 added support for connecting to multiple ZK services, but this
also introduced a bug that causes a cryptic NPE. The client sees the below sort
of error messages:
{noformat}
Exception while trying to create SASL client: java.lang.NullPointerException
SASL authentication with Zookeeper Quorum member failed:
javax.security.sasl.SaslException: saslClient failed to initialize properly:
it's null.
Error while calling watcher
java.lang.NullPointerException
at
org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.connectionEvent(ZooKeeperWatcher.java:581)
at
org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.process(ZooKeeperWatcher.java:532)
at
org.apache.hadoop.hbase.zookeeper.PendingWatcher.process(PendingWatcher.java:40)
at
org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:579)
at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:554)
{noformat}
The line at {{ZooKeeperWatcher.connectionEvent(ZooKeeperWatcher.java:581)}}
points to the middle line below, where {{event.getState()}} is {{null}}:
{noformat}
private void connectionEvent(WatchedEvent event) {
switch(event.getState()) {
case SyncConnected:
{noformat}
However, the event's state is {{null}} because of a couple of other bugs,
particularly an NPE that gets a mention in the log without a stacktrace. This
first NPE causes an incorrect initialization of the event and results in the
second NPE with the stacktrace.
The reason for the first NPE comes from this code in {{ZookeeperSaslClient}}:
{noformat}
if (!initializedLogin) {
...
}
Subject subject = login.getSubject();
{noformat}
Before the patch for ZOOKEEPER-2139, both the {{login}} and
{{initializedLogin}} were {{static}} fields of {{ZookeeperSaslClient}}. To
support multiple ZK clients, the {{login}} field was changed from {{static}} to
instance field, however the {{initializedLogin}} field was left as {{static}}
field. Because of this, the subsequent attempts to connect to ZK think that the
login doesn't need to be done and go ahead and blindly use the {{login}}
variable which causes the NPE.
At the core, the fix is simply to change {{initializedLogin}} to instance
variable, but we have made a few additional changes to improve the logging and
handle state. I will attach a patch soon.
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