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https://issues.apache.org/jira/browse/CURATOR-626?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17751449#comment-17751449
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Kezhu Wang commented on CURATOR-626:
------------------------------------
Hi [~tipame], would you mind opening a pull request for this ? I could take
over this in case you are not available.
> 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
> Priority: Major
> Fix For: 5.6.0
>
>
> 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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