[JBoss-user] [JBoss jBPM] - Re: Creating loops between nodes
Dear Elmo, I am trying the modify my code and run it, but I got a No row with the given identifier exists. Not sure why. BTW, I have tried the newProcessInstance() also. It runs but it suffers from performance and stack overflow issue. I guess we are not supposed to loop a ProcessInstance forever Thanks. Philip View the original post : http://www.jboss.com/index.html?module=bbop=viewtopicp=3927692#3927692 Reply to the post : http://www.jboss.com/index.html?module=bbop=postingmode=replyp=3927692 --- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnkkid=110944bid=241720dat=121642 ___ JBoss-user mailing list JBoss-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jboss-user
[JBoss-user] [JBoss jBPM] - Re: Creating loops between nodes
Hi Elmo, Ummm.. I am not very understand. You mean when ProcessInstance starts, in one of the nodes, it will create a separate thread, then the ProcessInstance will suspend, or return to main and save. When an event happens, this thread will load that ProcessInstance, and then continue its execution. Umm... I cannot figure out the looping mechanism. I guess above code implement the looping by not saving the ProcessInstance when it is invoked by the forked thread. Then next time when the forked thread loads the ProcessInstance again, it will load the ProcessInstance sits in the correct position. I don't know, I usually save the ProcessInstance immediately after I have used it. If I load the ProcessInstance from DB and let it run till the end, next time when I load and execute the same ProcessInstance again, it will said the ProcessInstance has already reached its end state. (Of course I can always move the token back to the start state by manipulating the token myself. But I guess it is always not preferred). I am reading async='true' now in chapter asynchronous continuations. I've tried adding the attribute into process definition, it doesn't work. I must have missed out something. Thanks. Philip View the original post : http://www.jboss.com/index.html?module=bbop=viewtopicp=3927376#3927376 Reply to the post : http://www.jboss.com/index.html?module=bbop=postingmode=replyp=3927376 --- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnkkid=110944bid=241720dat=121642 ___ JBoss-user mailing list JBoss-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jboss-user
[JBoss-user] [JBoss jBPM] - Re: Creating loops between nodes
This sample is an excerpt from arbitrary cycle of the workflow patterns:
| process-definition name=arbitrary-cycle
|
| start-state name=A
| transition to=B/
| /start-state
|
| state name=B
| timer duedate=20 seconds transition=C
|scriptprint( Your 20 seconds is up. Just letting you know I will
go to C now );/script
| /timer
| transition name=C to=C
| /state
|
| state name=C
| event type=node-enter
|action class=DoAsyncStuff/
| /event
| transition name=fail to=B/
| transition name=pass to=E/
| /state
|
| end-state name=E/
|
| /process-definition
|
This is the main execution part. Executed only once.
| JbpmContext ctx = config.createJbpmContext();
| try {
| ProcessInstance proc = ctx.newProcessInstance( arbitrary-cycle );
| proc.signal();
| ctx.save(proc);
| }
| catch(Exception ex)
| {
| ctx.setRollbackOnly();
| throw ex;
| }
| finally
| {
| ctx.close();
| }
|
In the EventListenerThread example from my previous code
|public void run() {
| //this class executes a long running process. It returns a status
| boolean pass = ALongRunningProcess.execute();
|
| JbpmContext ctx = config.createJbpmContext();
| try {
| ProcessInstance proc = ctx.newProcessInstance(
arbitrary-cycle );
| if( !pass )
| proc.signal(fail);
| else
| proc.signal(pass);
| ctx.save(proc);
| }
| catch(Exception ex)
| {
| ctx.setRollbackOnly();
| throw ex;
| }
| finally
| {
| ctx.close();
| }
| }
|
Take note: Running threads has some issues in a J2ee environment, also this
will not run if you restart the server. But thats another story. So this
example is just used to illustrate a point. In fact you can accomplish
something similar using timers instead. Hope this is clear.
Regards,
Elmo
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[JBoss-user] [JBoss jBPM] - Re: Creating loops between nodes
Oops sorry, must have been sleepy. In the thread you must retrieve the old
process instance not create a new one. Here is the correction
| public void run() {
| //this class executes a long running process. It returns a status
| boolean pass = ALongRunningProcess.execute();
|
| JbpmContext ctx = config.createJbpmContext();
| try {
| ProcessInstance proc = ctx.loadProcessInstance( processid );
| if( !pass )
| proc.signal(fail);
| else
| proc.signal(pass);
| ctx.save(proc);
| }
| catch(Exception ex)
| {
| ctx.setRollbackOnly();
| }
| finally
| {
| ctx.close();
| }
| }
Regards,
Elmo
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[JBoss-user] [JBoss jBPM] - Re: Creating loops between nodes
Hi Philip,
Sorry for the delayed response. We've been busy catching up on deadlines.
Anyway may I ask why this code, looping then redeploying?
| while (true) {
| jbpmConfiguration = null;
| processDefinition = null;
| jbpmContext = null;
| processInstance = null;
| try {
| jbpmConfiguration =
JbpmConfiguration.getInstance();
| processDefinition =
ProcessDefinition.parseXmlResource(MultipleEvent.par/processdefinition.xml);
| jbpmContext =
jbpmConfiguration.createJbpmContext();
|
jbpmContext.deployProcessDefinition(processDefinition);
| processInstance =
jbpmContext.loadProcessInstanceForUpdate(process_id);
| processInstance.resume();
| processInstance.signal();
| }
| finally {
| jbpmContext.close();
| }
| }
Just a quick thing. As I remeber, one JbpmSession allocates one DB connection.
Like I said, its not good to hold on to connections very long bec. normally
connections have timeouts, and connections are expensive resources. As I've
seen the code, it seems you are continually looping using the connection
without releasing it. I would suggest recoding esp. the action handler part.
Your action handler is denying your main connection to get closed, its like its
hogging it. What I suggest is use asynhronous transactions instead that signals
your state when finished. However, I am not quite familiar with the suspend
part and what it does to the connection, so I still have to check this one out.
Regards,
Elmo
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[JBoss-user] [JBoss jBPM] - Re: Creating loops between nodes
Hi Elmo, Sorry I keeps on bothering you. Hopefully I didn't interfere your normal work. Ummm... It is a long story. In our project, we wish to use jBPM engine to process incoming events. We treat a ProcessInstance as the big boss. When the program starts, a ProcessInstance will be created, process something and reached a wait state. The most simpliest ProcessDefinition we have created is something like this. | Start --- Event Listener --- Process it --- End1 | ^---+ | The ProcessInstance will terminate when some conditions are fulfilled. Say it has received an END event. We do not exactly knows how many loops it will loop through. In above scenario, it will loop forever until the user issued the END event. The problem arise when using loop. If I draw the graph this way, allowing jBPM to handle the loop, it will break with StackOverFlow after a few hundred rounds. I tried to learn from jBPM source code, and I guess it is because the nodes are called recursively, causing function stack overflow. I tried to bypass this problem by saving the ProcessInstance into database (anyway, my project needs to save everything into the database to guard against system crashes). When it has finished one cycle, it suspends and flushes everything. Then when another event arrives, it loads back the ProcessInstance, puts the event into Context variable, and starts again. This method somehow works (of course the performance is horrible, we are not supposed to code like this), but the memory consumed will grow slowly, and the performance will gradually decline. About the connection, I am not sure. I have opened MySQL Administrator to have a quick check. It has 10 DB connections on average. Looks like Hibernate's connection pool has handled most of the problem. I don't know how to check the no. of connections in Hibernate. I will see if I can find it out. If the no. of Hibernate connections keep on increasing, then it can explain why the program gradually stall. Let me rework my code to see if it improves. Keep in touch. Thanks for your help. Philip View the original post : http://www.jboss.com/index.html?module=bbop=viewtopicp=3927339#3927339 Reply to the post : http://www.jboss.com/index.html?module=bbop=postingmode=replyp=3927339 --- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnkkid=110944bid=241720dat=121642 ___ JBoss-user mailing list JBoss-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jboss-user
[JBoss-user] [JBoss jBPM] - Re: Creating loops between nodes
Hi Philip,
I'd just like to illustrate what I meant with an example. Why don't you try
it this way and tell me if it works for you:
| process-definition name=sample-event-listener
| start-state
| transition to=event-listener/
| /start-state
|
| state name=event-listener
| event type=node-enter
| action class=... /
| /event
| transition name=end-process to=end-state/
| /state
|
| end-state name=end-state/
|
| /process-definition
action handler class:
| public void execute(ExecutionContext ctx) throws Exception {
| long processid = ctx.getProcessInstance().getId();
|
| //since this is asynchronous, it will pass this immediately
| //and return handle to the main context
| AsyncEventListenerThread th = new AsyncEventListenerThread( id );
| th.start();
| }
the sample listener thread
| public class AsyncEventListenerThread extends Thread {
| long processid = processid;
|
| public AsyncEventListenerThread( long processid ) {
| this.processid = processid;
| }
|
| public void run() {
| //place your event listenter here. A JMS client would be good here
| //after event arrives, call a new JbpmSession, locate the process,
| //signal it and save and don't forget to close the jbpm context.
| }
| }
While you're at it, try also reading on asynchronous continuations. Maybe they
have something there that's already done for this job. I have not yet read on
that, let me know. Good luck.
Regards,
Elmo
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[JBoss-user] [JBoss jBPM] - Re: Creating loops between nodes
Hello Elmo, Thanks for your pointer. I have checked out the site and look like Pattern 10 (Arbitrary Cycle) and Pattern 11 (Implicit Termination) suitable my needs. I am trying to work on Pattern 10 right now. When I mimic the pattern in Process Definition, it run. But when it has run for a while, it threw a stack overflow exception. It looks to me if the no. of nested function calls reaches a certain limit, it will overflow. I have tried to bypass it by suspending the Process Instance, save it into database, clean up existing Process Instance, load, resume and continue. I do this every round. At the beginning, the performance is OK. However, when it has processed some events, say 200 rounds, its performance steadily drops. No exception has been thrown however. I am not very sure how to improves it. Please help. Thanks. Philip View the original post : http://www.jboss.com/index.html?module=bbop=viewtopicp=3926460#3926460 Reply to the post : http://www.jboss.com/index.html?module=bbop=postingmode=replyp=3926460 --- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnkkid=110944bid=241720dat=121642 ___ JBoss-user mailing list JBoss-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jboss-user
[JBoss-user] [JBoss jBPM] - Re: Creating loops between nodes
Hi Philip, My guess would be a database issue. How are you closing your transactions? You should not hold on to sessions for long periods. Saving should only take a few seconds, then the database connection should be released. For long transactions, it is preferrable to signal your process through asynchronous transactions, like JMS perhaps. Can you post your definition and code? I remember also having a stack overflow once but I cant quite remember. :( Regards, Elmo View the original post : http://www.jboss.com/index.html?module=bbop=viewtopicp=3926497#3926497 Reply to the post : http://www.jboss.com/index.html?module=bbop=postingmode=replyp=3926497 --- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnkkid=110944bid=241720dat=121642 ___ JBoss-user mailing list JBoss-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jboss-user
[JBoss-user] [JBoss jBPM] - Re: Creating loops between nodes
Elmo,
I am using MySQL 5.0.18. I am not sure if it is the cause of the problem.
Please find attached the processdefinition I am using. I draw it using
jBPM-Designer and then modify myself.
?xml version=1.0 encoding=UTF-8?
|
| process-definition
| xmlns=urn:jbpm.org:jpdl-3.1 name=MultipleEvent
|start-state name=start
| event type=node-enter
| action name=startAction
class=com.multipleevent.action.StartHandler/action
| /event
| transition name= to=Location/transition
|/start-state
|state name=Location
| event type=node-enter
| action name=locationAction
class=com.multipleevent.action.LocationHandler/action
| /event
| transition name=Location-Wait to=Wait/transition
| transition name=Location-Wait2 to=Wait2/transition
|/state
|node name=Wait
| event type=node-enter
| action name=waitAction
class=com.multipleevent.action.WaitHandler/action
| /event
| transition name= to=Process/transition
|/node
|state name=Process
| event type=node-enter
| action name=processAction
class=com.multipleevent.action.ProcessHandler/action
| /event
|/state
|node name=Wait2
| event type=node-enter
| action name=waitAction2
class=com.multipleevent.action.WaitHandler/action
| /event
| transition name=Wait2-Process2 to=Process2/transition
|/node
|state name=Process2
| event type=node-enter
| action name=processAction2
class=com.multipleevent.action.ProcessHandler/action
| /event
|/state
| /process-definition
|
The main driver is the Location handler, I ask the handler to visit each branch
by creating child tokens, then set the location back to Start, and suspend the
process.
public void execute(ExecutionContext executionContext) throws Exception
{
| Token token =
executionContext.getProcessInstance().getRootToken();
| Token childToken = null;
| ExecutionContext childExecutionContext = null;
|
| childToken = new Token(token, childToken);
| childExecutionContext = new ExecutionContext(childToken);
|
childExecutionContext.getNode().leave(childExecutionContext,Location-Wait);
|
| childToken = new Token(token, childToken2);
| childExecutionContext = new ExecutionContext(childToken);
|
childExecutionContext.getNode().leave(childExecutionContext,Location-Wait2);
|
|
executionContext.getToken().setNode(executionContext.getProcessDefinition().getNode(start));
| executionContext.getProcessInstance().suspend();
| }
In main, I write like this (The codes are very messy. I am sorry).
public void run() {
| JbpmConfiguration jbpmConfiguration = null;
| ProcessDefinition processDefinition = null;
|
| JbpmContext jbpmContext = null;
| ProcessInstance processInstance = null;
|
| try {
| jbpmConfiguration = JbpmConfiguration.getInstance();
| processDefinition =
ProcessDefinition.parseXmlResource(MultipleEvent.par/processdefinition.xml);
| jbpmContext = jbpmConfiguration.createJbpmContext();
| jbpmContext.deployProcessDefinition(processDefinition);
| processInstance =
jbpmContext.newProcessInstance(MultipleEvent);
| processInstance.signal();
| jbpmContext.save(processInstance);
| } finally {
| jbpmContext.close();
| }
|
| while (true) {
| jbpmConfiguration = null;
| processDefinition = null;
| jbpmContext = null;
| processInstance = null;
| try {
| jbpmConfiguration =
JbpmConfiguration.getInstance();
| processDefinition =
ProcessDefinition.parseXmlResource(MultipleEvent.par/processdefinition.xml);
| jbpmContext =
jbpmConfiguration.createJbpmContext();
|
jbpmContext.deployProcessDefinition(processDefinition);
| processInstance =
jbpmContext.loadProcessInstanceForUpdate(process_id);
| processInstance.resume();
| processInstance.signal();
| }
| finally {
| jbpmContext.close();
| }
| }
| }
Other Action handlers are just print outs.
When it was running, the JVM was growing
[JBoss-user] [JBoss jBPM] - Re: Creating loops between nodes
Hi Philip, I suggest you take a look at this site www.workflowpatterns.com, select a pattern there that meets your requirement and reference it. I think most people here are familiar with the site and makes it easy to understand what you want. It is also quite informative. Regards, Elmo View the original post : http://www.jboss.com/index.html?module=bbop=viewtopicp=3926427#3926427 Reply to the post : http://www.jboss.com/index.html?module=bbop=postingmode=replyp=3926427 --- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnkkid=110944bid=241720dat=121642 ___ JBoss-user mailing list JBoss-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jboss-user
