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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-3455) IPC.Client synchronisation looks weak
Date Wed, 28 May 2008 13:05:44 GMT
IPC.Client synchronisation looks weak
-------------------------------------

                 Key: HADOOP-3455
                 URL: https://issues.apache.org/jira/browse/HADOOP-3455
             Project: Hadoop Core
          Issue Type: Improvement
          Components: ipc
    Affects Versions: 0.18.0
            Reporter: Steve Loughran


Looking at HADOOP-3453 , its clear that Client.java is inconsistently synchronized

1. the running and shouldCloseConnection flags are not always read/written in synchronized
blocks, even though they are properties used to share information between threads. They should
be marked as volatile for access outside synchronized blocks, and all read-check-update operations
must be synchronized.

2. there are multiple calls to System.currentTimeMillis() in synchronized blocks; this is
a slow native operation and should ideally be done unsynchronized.

3. Synchronizing on the (out) stream is dangerous as its value changes during the life of
the class, and sometimes it is null. These blocks should all synchronize on the Client instead.

4.  There are a number of places where InterruptedExceptions are caught and ignored in a sleep-wait
loop:
     } catch (InterruptedException e) {
      }

   This isn't dangerous, but it does make the client harder to stop. These code fragments
should be looked at carefully.

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