[jira] Commented: (TUSCANY-2170) Synchronizing the access to SCADefinitions

["Ramkumar Ramalingam (JIRA)" <tu...@ws.apache.org>]

    [ https://issues.apache.org/jira/browse/TUSCANY-2170?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12584098#action_12584098 ] 

Ramkumar Ramalingam commented on TUSCANY-2170:
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Learnt that using Vectors OR Collections.synchronizedList synchronizes your list object. However, the iterators implemented in the java.util Collections classes are fail-fast, which means that if one thread changes a collection while another thread is traversing it through an Iterator, the next Iterator.hasNext() or Iterator.next() call will throw ConcurrentModificationException. If we have to prevent ConcurrentModificationException, we must lock the entire List while you are iterating by wrapping it with a synchronized block, which inturn is costly. 

As a solution to the above problem, the CopyOnWriteArrayList class from util.concurrent (which will also appear in the java.util.concurrent package in JDK 1.5) is a thread-safe implementation of ArrayList that offers far better concurrency. Multiple reads can almost always execute concurrently, simultaneous reads and writes can usually execute concurrently, and multiple simultaneous writes can often execute concurrently. Also CopyOnWriteArrayList contains a mutable reference to an immutable array, so as long as that reference is held fixed, you get all the thread-safety benefits of immutability without the need for locking. 

Hence i believe the best solution would be to go with CopyOnWriteArrayList instead of the current ArrayList used to store the list of policy sets, intents, binding types etc. 

Please suggest me if this one is the right approach. Thanks.

> Synchronizing the access to SCADefinitions
> ------------------------------------------
>
>                 Key: TUSCANY-2170
>                 URL: https://issues.apache.org/jira/browse/TUSCANY-2170
>             Project: Tuscany
>          Issue Type: Bug
>          Components: Java SCA Core Runtime
>    Affects Versions: Java-SCA-Next
>         Environment: SVN revision 642920 - Windows
>            Reporter: Ramkumar Ramalingam
>            Priority: Minor
>             Fix For: Java-SCA-Next
>
>
> http://www.mail-archive.com/tuscany-dev%40ws.apache.org/msg29138.html

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