On 29.03.2009 19:02, sebb wrote:
On 29/03/2009, [email protected]<[email protected]> wrote:
Author: rjung
Date: Sun Mar 29 14:17:16 2009
New Revision: 759694
URL: http://svn.apache.org/viewvc?rev=759694&view=rev
Log:
Fix locking in FastAsyncSocketSender:
Locking in DataSender and the sub class FastAsyncSocketSender
uses the same lock, although the reasons for locking are totally
independent.
- FastAsyncSocketSender only locks for assuring atomicity of internal
statistics counter manipulation.
- DataSender locks access to sockets and other things.
When a node crashes, sharing the same lock leads the request
handling threads to block in the replication valve, because
the replication sender thread keeps the lock while trying
to establish a new connection to the crashed node.
This problem stops, as soon as the membership drops the node,
but keeps a growing number of connector threads blocked
until that happens.
Using a separate mutex for the local statistics manipulations will
no longer block the request handling threads.
This is very useful info, but it's going to be tedious to find later
when looking at the code.
Or it could even be lost forever - does SVN keep track of log message changes?
May I suggest that it be added to the comments or Javadoc for the
class, or perhaps be added to package.html?
Thanks for the suggestion. I would say the comment on the new mutex
member should be enough. The verbose log message above aims at making
the the review of the commit/change easier. The shared lock should have
never been in place.
Modified:
tomcat/sandbox/tomcat-oacc/trunk/src/share/org/apache/catalina/cluster/tcp/FastAsyncSocketSender.java
Modified:
tomcat/sandbox/tomcat-oacc/trunk/src/share/org/apache/catalina/cluster/tcp/FastAsyncSocketSender.java
URL:
http://svn.apache.org/viewvc/tomcat/sandbox/tomcat-oacc/trunk/src/share/org/apache/catalina/cluster/tcp/FastAsyncSocketSender.java?rev=759694&r1=759693&r2=759694&view=diff
==============================================================================
---
tomcat/sandbox/tomcat-oacc/trunk/src/share/org/apache/catalina/cluster/tcp/FastAsyncSocketSender.java
(original)
+++
tomcat/sandbox/tomcat-oacc/trunk/src/share/org/apache/catalina/cluster/tcp/FastAsyncSocketSender.java
Sun Mar 29 14:17:16 2009
@@ -92,6 +92,13 @@
private int threadPriority = Thread.NORM_PRIORITY;;
+ /**
+ * Separate mutex for our local state.
+ * We keep the synchronization independent of the synchronization
+ * in the super class DataSender.
+ */
+ private Object mutex = new Object();
+
// -------------------------------------------------------------
Constructor
/**
@@ -354,7 +361,7 @@
public void sendMessage(ClusterData data)
throws java.io.IOException {
queue.add(data.getUniqueId(), data);
- synchronized (this) {
+ synchronized (mutex) {
inQueueCounter++;
if(queueThread != null)
queueThread.incQueuedNrOfBytes(data.getMessage().length);
@@ -456,15 +463,15 @@
return queuedNrOfBytes;
}
- protected synchronized void setQueuedNrOfBytes(long queuedNrOfBytes)
{
+ protected void setQueuedNrOfBytes(long queuedNrOfBytes) {
this.queuedNrOfBytes = queuedNrOfBytes;
}
- protected synchronized void incQueuedNrOfBytes(long size) {
+ protected void incQueuedNrOfBytes(long size) {
queuedNrOfBytes += size;
}
- protected synchronized void decQueuedNrOfBytes(long size) {
+ protected void decQueuedNrOfBytes(long size) {
queuedNrOfBytes -= size;
}
@@ -562,8 +569,10 @@
.getKey()), x);
}
} finally {
- outQueueCounter++;
- decQueuedNrOfBytes(messagesize);
+ synchronized (sender.mutex) {
+ outQueueCounter++;
+ decQueuedNrOfBytes(messagesize);
+ }
}
entry = entry.next();
} while (keepRunning&& entry != null);
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