RE: RE: Concurrent requests and Orchestra

[Vojtech Zavrel]

Thank you for the quick answer,
this is the information I wanted to know. It is well described in JavaDoc
http://myfaces.apache.org/orchestra/myfaces-orchestra-core/apidocs/org/apache/myfaces/orchestra/CoreConfig.html#SERIALIZE_REQUESTS,
but I didn't find this information on the project web page.
Generally I also think it is bad idea to change default concurrency behavior
of accessing to scoped objects and even not advise of it.

Regards Vojtech

RE: Concurrent requests and Orchestra

Mario Ivankovits
Thu, 20 Aug 2009 02:26:25 -0700

Hi!

A PersistenceContext is not thread safe, therefore, Orchestra tries to avoid

that by locking the request.
It would be nice, if Orchestra does this just for requests requireing a
PersistenceContext. But till today, we did not manage to spend some time to
optimize that code.

You can set the webapp init parameter
org.apache.myfaces.orchestra.CoreConfig:SERIALIZE_REQUESTS to false so that
Orchestra does not check for thread safety.

You then have to ensure threadsafety against the PersistenceContext yourself

(which might not be easy … not to say, impossible :-( )

Ciao,
Mario

Concurrent requests and Orchestra

[Vojtech Zavrel]

 Hi,
 we have a problem with concurrent request using combination Orchestra +
Spring + Trinidad. The application uses more than one window per session, so
we have migrated all our beans to orchestra's conversation scope using
conversation.manual.
We have a progress bar which is poling AJAX request during the main request
is being done. Once user is waiting to the main request, there are partial
requests each five seconds using Trinidad Javascript API. To be able handle
more requests the partial request goes in another frame with same
conversationContext.
Both partial and full request are accessing to the same bean. And this is
the problem because there is there is ReentrantLock used not to be able to
access to FacesContex from different thread. So that means, that we are not
able to access to the progressbar model and the partial request is locked
till the full request is finished. But I haven't understood why there is
this concurrent limitatins because they aren't in other scopes.

This is the comment from the source code:

// Fetch a context for this request if one already exists, and lock it
72 // so that concurrent requests that affect this context block until
73 // this request is complete. Not doing so can cause races for resources
74 // within the current context, such as beans or PersistenceContexts.

But what kind of races and why there are not same problems using other
scopes. Can anybody explain me the reasons please? Is there any possibility
how to make a workaround?

Thanks


Daemon Thread [http-8080-1] (Suspended)
Object.wait(long) line: not available [native method] [local variables
unavailable]
_ReentrantLock.lockInterruptibly() line: 80
ConversationContext.lockInterruptablyForCurrentThread() line: 475
ContextLockRequestHandler.init(FacesContext) line: 96
OrchestraFacesContextFactory$1.(OrchestraFacesContextFactory,
FacesContext, boolean, LinkedList, FacesContext) line: 119
OrchestraFacesContextFactory.getFacesContext(Object, Object, Object,
Lifecycle) line: 100
RequestParameterFacesContextFactory.getFacesContext(Object, Object, Object,
Lifecycle) line: 92
FacesContextFactoryImpl.getFacesContext(Object, Object, Object, Lifecycle)
line: 64
FacesServlet.service(ServletRequest, ServletResponse) line: 260
ApplicationFilterChain.internalDoFilter(ServletRequest, ServletResponse)
line: 290
ApplicationFilterChain.doFilter(ServletRequest, ServletResponse) line: 206
TrinidadFilterImpl._invokeDoFilter(ServletRequest, ServletResponse,
FilterChain) line: 238
TrinidadFilterImpl._doFilterImpl(ServletRequest, ServletResponse,
FilterChain) line: 195
TrinidadFilterImpl.doFilter(ServletRequest, ServletResponse, FilterChain)
line: 138
TrinidadFilter.doFilter(ServletRequest, ServletResponse, FilterChain) line:
92
ApplicationFilterChain.internalDoFilter(ServletRequest, ServletResponse)
line: 235
ApplicationFilterChain.doFilter(ServletRequest, ServletResponse) line: 206
LicenseFilter.doFilter(ServletRequest, ServletResponse, FilterChain) line:
123
ApplicationFilterChain.internalDoFilter(ServletRequest, ServletResponse)
line: 235
ApplicationFilterChain.doFilter(ServletRequest, ServletResponse) line: 206
ResponseHeaderFilter.doFilter(ServletRequest, ServletResponse, FilterChain)
line: 54
ApplicationFilterChain.internalDoFilter(ServletRequest, ServletResponse)
line: 235
ApplicationFilterChain.doFilter(ServletRequest, ServletResponse) line: 206
SessionTimeoutFilter.doFilter(ServletRequest, ServletResponse, FilterChain)
line: 116
ApplicationFilterChain.internalDoFilter(ServletRequest, ServletResponse)
line: 235
ApplicationFilterChain.doFilter(ServletRequest, ServletResponse) line: 206
StandardWrapperValve.invoke(Request, Response) line: 233
StandardContextValve.invoke(Request, Response) line: 175
StandardHostValve.invoke(Request, Response) line: 128
ErrorReportValve.invoke(Request, Response) line: 102
StandardEngineValve.invoke(Request, Response) line: 109
CoyoteAdapter.service(Request, Response) line: 263
Http11Processor.process(Socket) line: 844
Http11Protocol$Http11ConnectionHandler.process(Socket) line: 584
JIoEndpoint$Worker.run() line: 447
Thread.run() line: 619