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https://issues.apache.org/jira/browse/DIRMINA-819?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Emmanuel Lecharny closed DIRMINA-819.
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> Synchronous behavior while adding and removing connections
> ----------------------------------------------------------
>
> Key: DIRMINA-819
> URL: https://issues.apache.org/jira/browse/DIRMINA-819
> Project: MINA
> Issue Type: Bug
> Affects Versions: 2.0.0-RC1, 2.0.0, 2.0.1, 2.0.2
> Environment: java version "1.6.0_22"
> Java(TM) SE Runtime Environment (build 1.6.0_22-b04)
> Java HotSpot(TM) 64-Bit Server VM (build 17.1-b03, mixed mode)
> Reporter: John R. Fallows
> Assignee: Emmanuel Lecharny
> Fix For: 2.0.3
>
> Attachments: sync.patch
>
>
> We discovered some blocking behavior in the Mina AbstractPollingIoProcessor
> that is triggered while adding and removing connections.
> This class manages an internal worker that must be started when the first
> connection is added, and stopped when the last connection is removed.
> The code achieves this by using a synchronized block in startupProcessor() as
> follows:
> public final void remove(T session) {
> scheduleRemove(session);
> startupProcessor();
> }
> private void scheduleRemove(T session) {
> removingSessions.add(session);
> }
> private void startupProcessor() {
> synchronized (lock) {
> if (processor == null) {
> processor = new Processor();
> executor.execute(new NamePreservingRunnable(processor,
> threadName));
> }
> }
> // Just stop the select() and start it again, so that the processor
> // can be activated immediately.
> wakeup();
> }
> Each call to session.close() triggers the "filterClose" event on the filter
> chain, ending in a call to removeSession (shown above) where the synchronized
> lock is obtained to verify that the processor is running in order to close
> the connection. When a large number of connections are closed at the same
> time, they will contend for the synchronized lock. Similar behavior occurs
> when new connections are established via addSession (not shown here). Both
> removeSession and addSession synchronize on the same lock, so they also
> contend with each other as connections come and go.
> Note that we found similar behavior in AbstractPollingIoAcceptor and
> AbstractPollingIoConnector as well.
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