Arup Malakar created HCATALOG-627:
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Summary: NotificationListener is not thread safe
Key: HCATALOG-627
URL: https://issues.apache.org/jira/browse/HCATALOG-627
Project: HCatalog
Issue Type: Bug
Affects Versions: 0.5, 0.4, 0.6
Reporter: Arup Malakar
Assignee: Arup Malakar
>From the code in
>[HiveMetaStore|http://svn.apache.org/repos/asf/hive/trunk/metastore/src/java/org/apache/hadoop/hive/metastore/HiveMetaStore.java]
> it appears that only one instance of the provided listener is created which
>then gets used by the thread pool. But the methods in the
>NotificationListnener in HCatalog is not threadsafe. For example according to
>JMS api documentation a Connection object can be shared among threads, but the
>[Session|http://docs.oracle.com/javaee/1.4/api/javax/jms/Session.html] [1]
>object should be specific to a thread.
| A Session object is a single-threaded context for producing and consuming
messages. Although it may allocate provider resources outside the Java virtual
machine (JVM), it is considered a lightweight JMS object.
But NotificationListener has only one session object which gets shared among
threads. While testing I have observed cases where messages were getting
drooped, using a ThreadLocal Session solved the problem for me. But I am
interested in knowing if anyone else has seen dropped messages.
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