Viktor Feklin created CURATOR-626:
-------------------------------------
Summary: NullPointerException in watcher of nullNamespace
Key: CURATOR-626
URL: https://issues.apache.org/jira/browse/CURATOR-626
Project: Apache Curator
Issue Type: Bug
Components: Framework
Affects Versions: 5.2.0
Reporter: Viktor Feklin
NPE processing lock released event:
{code:java}
java.lang.NullPointerException: null
at
java.util.concurrent.CompletableFuture.screenExecutor(CompletableFuture.java:415)
at
java.util.concurrent.CompletableFuture.runAsync(CompletableFuture.java:1871)
at
org.apache.curator.framework.imps.CuratorFrameworkImpl.runSafe(CuratorFrameworkImpl.java:191)
at
org.apache.curator.framework.CuratorFramework.postSafeNotify(CuratorFramework.java:344)
at
org.apache.curator.framework.recipes.locks.LockInternals$2.process(LockInternals.java:69)
at
org.apache.curator.framework.imps.NamespaceWatcher.process(NamespaceWatcher.java:77)
at
org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:535)
at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:510)
{code}
Steps to reproduce:
{code:java}
InterProcessMutex lock = new
InterProcessMutex(curatorFramework.usingNamespace(null), path);
lock.acquire();{code}
If lock is holded by another process (at the moment of call) - we will never
acquire it (after lock was released by holder) because notification event lost
while processing on watcher.
The root cause of bug - is wrong init code of СuratorFrameworkImpl:
{code:java}
public CuratorFrameworkImpl(CuratorFrameworkFactory.Builder builder)
{
....
failedDeleteManager = new FailedDeleteManager(this);
failedRemoveWatcherManager = new FailedRemoveWatchManager(this);
// here you pass not fully initialized instance (this)
namespaceFacadeCache = new NamespaceFacadeCache(this);
ensembleTracker = zk34CompatibilityMode ? null : new EnsembleTracker(this,
builder.getEnsembleProvider());
runSafeService = makeRunSafeService(builder);
} {code}
In NamespaceFacadeCache:
{code:java}
NamespaceFacadeCache(CuratorFrameworkImpl client)
{
this.client = client;
// here you create facade for null namespace based on not fully initialized
client
nullNamespace = new NamespaceFacade(client, null);
} {code}
NamespaceFacade - clones client fields, but not all fields initialized at this
moment:
ensembleTracker and runSafeService - are both nulls
So then we use null namespace - we use this broken client and get NPE on access
this null fields (se stacktrace).
Fix is very easy:
{code:java}
public CuratorFrameworkImpl(CuratorFrameworkFactory.Builder builder)
{
...
failedDeleteManager = new FailedDeleteManager(this);
failedRemoveWatcherManager = new FailedRemoveWatchManager(this);
ensembleTracker = zk34CompatibilityMode ? null : new EnsembleTracker(this,
builder.getEnsembleProvider());
runSafeService = makeRunSafeService(builder);
// initialization of cache should be the last operation in init method (all
fields are initialized)
namespaceFacadeCache = new NamespaceFacadeCache(this);
} {code}
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