Re: [rap-dev] Various issues running RAP in a clustered envorinment
Hi Clemens,
sorry for the late response, but it's summer time and most of as are on
vacation.
RAP dev mailing list is for RAP project development discussions. Please
post your questions in RAP Newsgroup [1].
As you already mentioned, the clustering environment is tricky. On the
Newsgroup you will get help from other RAP users with similar problems
faster.
[1] https://www.eclipse.org/forums/index.php?t=thread_id=34
Best regards,
Ivan
On 7/26/2017 11:35, Clemens Eisserer wrote:
Hello,
I wonder, is anybody using RAP on a session-replicated cluster?
For the last few days I was trying to get my RAP based project to play
nicely in a clustered environment.
However, after fixing all the application-related issues, I still see
strange behaviour, most likely caused by RAP.
The environment is rather tricky: 2x Tomcat application servers +
Apache+mod_jk round-robin load balancer
The load-balancer is alternating between the two Tomcat instances for
every request, which means high requirements regarding session
replication consistency.
Unfourtunately the environment is as-is, later the application has to
run in an environment behaving like this one.
RAP is configured with OperationMode.SESSION_FAILOVER and
and in principle, session replication seems to work.
Tomcat was configured with SimpleTcpCluster and channelSendOptions="6"
(synchrounous session replication with ACK - according to the tomcat
users mailing list the strictest setting Tomcat has.).
However even with the simple example below, I get strange behaviour
and issues: https://youtu.be/p5u2z-NjIs0
Sometimes request/response pairs are sent for 30s.
And for a larger real-world app I also get sometimes:
- HTTP-500 and HTTP-412
- ConcurrentModificationException during Session Serialization
(Collection is modified concurrently while being serialized)
- Various other exceptions listed below.
- ClientListener is not Serializeable
I had a look at RAP's source, but I am a bit lost:
* ClientListener not implementing Serializeable was easy to fix and
seems to work.
* I guess the ConcurrentModificationException during seerialization is
tough and it seems I am not the only one expoeriencing this:
https://www.eclipse.org/forums/index.php/t/532053/
I wrote my own servlet filter (running before/after RWTClusterSupport)
serializing all session attributes to disk, *removing* the attributes,
and re-loading them again at the next request and ran into issues of
UISessionImpl.attributes beeing empty. I saw
UISessionImpl.get/setAttribute is synchronized, is this supposed to be
accessed by multiple threads? If so, synchronization has no effect on
the app servers synchronization during session replication - it will
simply snapshot some inconsistent state).
* What could cause the client to immediatly re-execute a new request
after receiving a response? Maybe this could be a starting point to
debug the request/response storms I am experiencing.
Thank you in advance and best regards, Clemens
public class BasicEntryPoint extends AbstractEntryPoint {
protected void createContents(Composite parent) {
Tree tree;
ScrolledComposite scroll = new ScrolledComposite(parent, SWT.V_SCROLL);
tree = new Tree(scroll, SWT.BORDER);
scroll.setContent(tree);
scroll.setExpandHorizontal(true);
scroll.setExpandVertical(true);
tree.addSelectionListener(new SelectionAdapter() {
public void widgetSelected(SelectionEvent se) {
if(tree.getSelectionCount() > 0) {
TreeItem item = tree.getSelection()[0];
item.setText(item.getText() + "_");
}}
});
for(int i=0; i < 10; i++) {
TreeItem item = new TreeItem(tree, SWT.NONE);
item.setText("MainItem " + i);
for(int m=0; m < 10; m++) {
TreeItem childItem = new TreeItem(item, SWT.NONE);
childItem.setText("Child: "+m);
}
}
}
}
Tomcat cluster configuration:
- java.lang.NullPointerException
at
org.eclipse.rap.rwt.SingletonUtil.getUniqueInstance(SingletonUtil.java:74)
at
org.eclipse.rap.rwt.internal.lifecycle.RequestCounter.getInstance(RequestCounter.java:25)
at
org.eclipse.rap.rwt.internal.service.LifeCycleServiceHandler.isRequestCounterValid(LifeCycleServiceHandler.java:133)
at
org.eclipse.rap.rwt.internal.service.LifeCycleServiceHandler.processUIRequest(LifeCycleServiceHandler.java:94)
at
org.eclipse.rap.rwt.internal.service.LifeCycleServiceHandler.synchronizedService(LifeCycleServiceHandler.java:75)
at
org.eclipse.rap.rwt.internal.service.LifeCycleServiceHandler.service(LifeCycleServiceHandler.java:66)
at
[rap-dev] Various issues running RAP in a clustered envorinment
Hello,
I wonder, is anybody using RAP on a session-replicated cluster?
For the last few days I was trying to get my RAP based project to play
nicely in a clustered environment.
However, after fixing all the application-related issues, I still see
strange behaviour, most likely caused by RAP.
The environment is rather tricky: 2x Tomcat application servers +
Apache+mod_jk round-robin load balancer
The load-balancer is alternating between the two Tomcat instances for
every request, which means high requirements regarding session
replication consistency.
Unfourtunately the environment is as-is, later the application has to
run in an environment behaving like this one.
RAP is configured with OperationMode.SESSION_FAILOVER and
and in principle, session replication seems to work.
Tomcat was configured with SimpleTcpCluster and channelSendOptions="6"
(synchrounous session replication with ACK - according to the tomcat
users mailing list the strictest setting Tomcat has.).
However even with the simple example below, I get strange behaviour
and issues: https://youtu.be/p5u2z-NjIs0
Sometimes request/response pairs are sent for 30s.
And for a larger real-world app I also get sometimes:
- HTTP-500 and HTTP-412
- ConcurrentModificationException during Session Serialization
(Collection is modified concurrently while being serialized)
- Various other exceptions listed below.
- ClientListener is not Serializeable
I had a look at RAP's source, but I am a bit lost:
* ClientListener not implementing Serializeable was easy to fix and
seems to work.
* I guess the ConcurrentModificationException during seerialization is
tough and it seems I am not the only one expoeriencing this:
https://www.eclipse.org/forums/index.php/t/532053/
I wrote my own servlet filter (running before/after RWTClusterSupport)
serializing all session attributes to disk, *removing* the attributes,
and re-loading them again at the next request and ran into issues of
UISessionImpl.attributes beeing empty. I saw
UISessionImpl.get/setAttribute is synchronized, is this supposed to be
accessed by multiple threads? If so, synchronization has no effect on
the app servers synchronization during session replication - it will
simply snapshot some inconsistent state).
* What could cause the client to immediatly re-execute a new request
after receiving a response? Maybe this could be a starting point to
debug the request/response storms I am experiencing.
Thank you in advance and best regards, Clemens
public class BasicEntryPoint extends AbstractEntryPoint {
protected void createContents(Composite parent) {
Tree tree;
ScrolledComposite scroll = new ScrolledComposite(parent, SWT.V_SCROLL);
tree = new Tree(scroll, SWT.BORDER);
scroll.setContent(tree);
scroll.setExpandHorizontal(true);
scroll.setExpandVertical(true);
tree.addSelectionListener(new SelectionAdapter() {
public void widgetSelected(SelectionEvent se) {
if(tree.getSelectionCount() > 0) {
TreeItem item = tree.getSelection()[0];
item.setText(item.getText() + "_");
}}
});
for(int i=0; i < 10; i++) {
TreeItem item = new TreeItem(tree, SWT.NONE);
item.setText("MainItem " + i);
for(int m=0; m < 10; m++) {
TreeItem childItem = new TreeItem(item, SWT.NONE);
childItem.setText("Child: "+m);
}
}
}
}
Tomcat cluster configuration:
- java.lang.NullPointerException
at
org.eclipse.rap.rwt.SingletonUtil.getUniqueInstance(SingletonUtil.java:74)
at
org.eclipse.rap.rwt.internal.lifecycle.RequestCounter.getInstance(RequestCounter.java:25)
at
org.eclipse.rap.rwt.internal.service.LifeCycleServiceHandler.isRequestCounterValid(LifeCycleServiceHandler.java:133)
at
org.eclipse.rap.rwt.internal.service.LifeCycleServiceHandler.processUIRequest(LifeCycleServiceHandler.java:94)
at
org.eclipse.rap.rwt.internal.service.LifeCycleServiceHandler.synchronizedService(LifeCycleServiceHandler.java:75)
at
org.eclipse.rap.rwt.internal.service.LifeCycleServiceHandler.service(LifeCycleServiceHandler.java:66)
at
org.eclipse.rap.rwt.engine.RWTServlet.handleValidRequest(RWTServlet.java:135)
at org.eclipse.rap.rwt.engine.RWTServlet.handleRequest(RWTServlet.java:117)
at org.eclipse.rap.rwt.engine.RWTServlet.doPost(RWTServlet.java:107)
java.lang.NullPointerException
org.eclipse.swt.graphics.ImageSerializer.getResourceManager(ImageSerializer.java:95)
org.eclipse.swt.graphics.ImageSerializer.access$1(ImageSerializer.java:94)
org.eclipse.swt.graphics.ImageSerializer$PostDeserializationValidation$1.run(ImageSerializer.java:53)
