[jbossseam-issues] [JBoss JIRA] Created: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
12:31 p.m.
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.1.0.GA, 2.0.3.CR1, 2.0.2.SP1
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Priority: Blocker
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope" components
this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
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4:57 p.m.
New subject: [jbossseam-issues] [JBoss JIRA] Updated: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Pete Muir updated JBSEAM-3652:
------------------------------
Fix Version/s: 2.1.1.CR1
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Priority: Blocker
Fix For: 2.1.1.CR1
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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8:13 p.m.
New subject: [jbossseam-issues] [JBoss JIRA] Assigned: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Shane Bryzak reassigned JBSEAM-3652:
------------------------------------
Assignee: Shane Bryzak
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Shane Bryzak
Priority: Blocker
Fix For: 2.1.1.CR1
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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2:02 a.m.
New subject: [jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Shane Bryzak commented on JBSEAM-3652:
--------------------------------------
I can't seem to reproduce this issue, could you please attach a minimal test case
including steps to reproduce. In response to your questions:
1) Seam will synchronize access to session scoped components, and as described by the docs
it also enforces a single thread per conversation model. The page context is
single-threaded in nature (a new page context is created for each request).
2) From memory there is a good reason why we only outject for the last concurrent thread,
however off the top of my head I can't remember what it is. I'll bring it up on
the seam-dev mailing list (and try to document it in the code also once I have an
answer).
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Shane Bryzak
Priority: Blocker
Fix For: 2.1.1.CR1
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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10:35 a.m.
New subject: [jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Dan Allen commented on JBSEAM-3652:
-----------------------------------
Add @Synchronized to your component. Page-scoped components aren't synchronized by
default, which is a problem if you are using sever-side state saving. We will discuss
making this the default.
And yes, bijection assumes that a component is only being accessed from a single thread at
a time.
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Shane Bryzak
Priority: Blocker
Fix For: 2.1.1.CR1
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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1:32 p.m.
New subject: [jbossseam-issues] [JBoss JIRA] Updated: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Denis Forveille updated JBSEAM-3652:
------------------------------------
Attachment: traces.txt
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Shane Bryzak
Priority: Blocker
Fix For: 2.1.1.CR1
Attachments: Test3652.java, Test3652Conv.java, testJBSEAM3652.xhtml, traces.txt
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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1:32 p.m.
New subject: [jbossseam-issues] [JBoss JIRA] Updated: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Denis Forveille updated JBSEAM-3652:
------------------------------------
Attachment: Test3652.java
Test3652Conv.java
testJBSEAM3652.xhtml
Shane, I created a simple test case that shows the problem and I think I hit another bug,
ie that the method annotated with "@Create" may be called many times for a page
scope component even if it should not (I guess)
I uploaded the traces produced by 4 tests cases:
For the 4 cases, I clicked 6 times quickly on the link. The results:
Case 1 : We have a call in the ".xhtml" file that triggers the creation of the
component before the user can click on the link and we don't use long running
conversation
-> This illustrates the bug mentionned before in BijectionInterceptor. The component in
conversation scope is shared between calls until BijectionInterceptore disinject it as
described in my initial post (ie becomes null for one of the thread), then another
instance of this component is automaticaly created.
-> Calls to the "testMethod" method are not serialized as confirmed by the
post of Dan
-> Q: Besides the NPE, should'nt we have 6 different instances of the conversation
scoped component there as we are not in a long running conversation??
Case 2: The component is created when the user clics on the link and we don't use
long running conversation
-> @Create is called 6 times (!!!!), creating 6 different instances of the conversation
scope component. Wow !!!
-> Calls to the "testMethod" method are not serialized as confirmed by the
post of Dan
Case 3: We have a call in the .xhtml that triggers the creation of the component and we
have a long running conversation started on @Create
-> Works as expected, I guess: @Create si called only once, and calls to the
"testMethod" method are serialized
Case 4: The component is created when the user clics on the link and and we have a long
running conversation started on @Create
-> Quite similar to test case 2
-> @Create is called 6 times (!!!!), creating 6 different instances of the conversation
scope component. Wow !!!
-> Calls to the "testMethod" method are not serialized, because I think the
@Create methiod created 6 instances of the conversation scope component
To summarise:
1) this shows clearly the bug in BijectioNinterceptor (case 1)
2) there is another bug where @Create can be called many time for the same page scope
component
3) IMHO, page scope component should almost always be annotated with @Synchronized to
solve some forms of "double clics".
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Shane Bryzak
Priority: Blocker
Fix For: 2.1.1.CR1
Attachments: Test3652.java, Test3652Conv.java, testJBSEAM3652.xhtml, traces.txt
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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9:37 p.m.
New subject: [jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Shane Bryzak commented on JBSEAM-3652:
--------------------------------------
So just to be clear, does adding @Synchronized as Dan suggested fix all of the issues that
you are seeing?
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Shane Bryzak
Priority: Blocker
Fix For: 2.1.1.CR1
Attachments: Test3652.java, Test3652Conv.java, testJBSEAM3652.xhtml, traces.txt
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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7:33 a.m.
New subject: [jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Denis Forveille commented on JBSEAM-3652:
-----------------------------------------
No. The problems are there even with @Synchronized for case 2 and case 4
- It appears that the calls to the method annotated with "@Create" is not
serialized/synchronized causing major problems in the creation of the component and of the
dependent components
- your comment suggests that there is no bug in BijectionInterceptor and the solution is
to use @Synchronized. Please read the source code of the BijectionInterceptor class with
the comment I made in my first posts and you'll see clearly that there is one
"counter--" too much in the code causing case 1. using @Synchronized there is
just a "workaround" to a bigger problem IMHO
You can easily run the test case I uploaded at your request to reproduce the problems.
Comment/uncomment the "@Begin" line in the java code, and /or comment/uncomment
line "<h:outputText id="hello" value="#{test3652.hello}"
/>" in the xhtml
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Dan Allen
Priority: Blocker
Fix For: 2.1.1.CR1
Attachments: Test3652.java, Test3652Conv.java, testJBSEAM3652.xhtml, traces.txt
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
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11:33 p.m.
New subject: [jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Dan Allen commented on JBSEAM-3652:
-----------------------------------
I thoroughly studied the attached cases as well as the existing unit tests and have
answers/responses to all of your questions.
You were correct that there was a bug in the counter logic. Both finally blocks were
decrementing the counter for the same invocation. I have changed it so that the first
finally block consults the value of the counter without changing the value. I also changed
the field name from "counter" to "client" to make it more apparent
that we are counting client threads.
Fixing the counter bug brings the other observations into focus. Let's take each test
scenario in turn.
Case 1: An instance of the page-scoped component exists at the time the user clicks on the
button to activate one of its methods. No long-running conversation exists.
If the page-scoped component is not synchronized, then each concurrent click will invoke
the same page-scoped component, but the conversation-scoped component will only be
injected on the first invocation since injection does not happen again until the component
has no more clients (invoking threads). That is why you only see one instance of the
conversation-scoped component and not one per click. If you add @Synchronized to the
page-scoped component, then each click is processed in turn, and then you have one
conversation-scoped component created and injected per click. Page-scoped components are
now synchronized by default.
Case 2: The page-scoped component is created when the user clicks on the link. No
long-running conversation exists.
In this case, a new page-scoped component created (and in turn a new conversation-scoped
component created and injected) per click. The reason is that Seam only flushes the page
context held in a thread local at the end of the request. Thus, even though you are
invoking a command button from the same view, the newly created page-scoped component is
not yet associated with that UI component tree. In this case, it's really like 6
different requests because none of the requests know that the other requests have also
created a page-scoped component.
Case 3: An instance of the page-scoped component exists at the time the user clicks on the
button to activate on of its methods. A long-running conversation is active.
In this case, a long-running conversation is active and Seam is serializing access to that
conversation. Therefore, the page-scoped component is naturally protected against
concurrent access. Essentially, access to the entire UI component tree is being serialized
by the conversation.
Case 4: The page-scoped component is created when the user clicks on the link, also
creating a long-running conversation.
Exactly the same explanation as Case #2.
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Dan Allen
Priority: Blocker
Fix For: 2.1.1.CR1
Attachments: Test3652.java, Test3652Conv.java, testJBSEAM3652.xhtml, traces.txt
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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11:35 p.m.
New subject: [jbossseam-issues] [JBoss JIRA] Resolved: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Dan Allen resolved JBSEAM-3652.
-------------------------------
Resolution: Done
Labels: concurrency (was: )
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Dan Allen
Priority: Blocker
Fix For: 2.1.1.CR1
Attachments: Test3652.java, Test3652Conv.java, testJBSEAM3652.xhtml, traces.txt
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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12:56 p.m.
New subject: [jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Denis Forveille commented on JBSEAM-3652:
-----------------------------------------
Thanks for the fix in BijectionInterceptor Dan
However, for case #2, this breaks the contract of the @Create annotation that should be
called only once per component in its scope IMHO.
With or without @Synchronized, @Create is called many times foir the same component/scope
in that case. I think calls to @Create should be serialized too. In our case this causes
majors inconsistencies (Even with @Synchronized)
If you want me to create a separate jira for that, please let me know
Also what do you mean by "Page-scoped components are now synchronized by default.
"? Did You changed that for v2.1.1? we are about to add @Synchronized to all our page
scope components, maybe we'll wait until v2.1.1 then..
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Dan Allen
Priority: Blocker
Fix For: 2.1.1.CR1
Attachments: Test3652.java, Test3652Conv.java, testJBSEAM3652.xhtml, traces.txt
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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3:25 p.m.
New subject: [jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Dan Allen commented on JBSEAM-3652:
-----------------------------------
I'll start with the easy question. Yes, in 2.1.1 I added @Synchronized to page-scoped
components. However, if there is a chance that the user really will double submit the
form, and you want both calls to succeed, I would suggest adding @Synchronized because the
default timeout is pretty short and will likely cause one of the calls to timeout
(resulting in an error page).
Okay, back to case #2. This is one of those points where it is hard to find the right
words to explain what is going on, but I will keep trying. First, @Create methods *are*
synchronized by Seam, just like any other business method on a @Synchronized component.
What you are observing is something entirely different. As far as Seam is concerned, the
page scope remains untouched until the end of the request. Thus, if you submit a UI
command button N times in parallel, then there is no communication between those N
thread-local page scopes (in terms of the addition of new variables). Thus, all N requests
think they need to instantiate the page-scoped component and therefore you get N
instances. That means N calls to a @Create method, but each call happens on a different
instance (this is not a synchronization problem in that regard). At the beginning and end
of the render phase, the thread-local page scope is flushed to the UI component tree. At
that point, the last request wins and overwrites the instances created by the other N - 1
requests.
What we would need to avoid this situation is for access to the UI component tree to be
synchronized, in the same way that access to the conversation is synchronized. It cannot
be solved at the component level.
BTW, the buffered page context variables are placed into the faces view root at the
beginning of the render phase.
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Dan Allen
Priority: Blocker
Fix For: 2.1.1.CR1
Attachments: Test3652.java, Test3652Conv.java, testJBSEAM3652.xhtml, traces.txt
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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2:24 p.m.
New subject: [jbossseam-issues] [JBoss JIRA] Closed: (JBSEAM-3652) Major reentrancy problem with "Page Scope" components and injection/disinjection
[
https://jira.jboss.org/jira/browse/JBSEAM-3652?page=com.atlassian.jira.pl...
]
Denis Forveille closed JBSEAM-3652.
-----------------------------------
Major reentrancy problem with "Page Scope" components and
injection/disinjection
--------------------------------------------------------------------------------
Key: JBSEAM-3652
URL: https://jira.jboss.org/jira/browse/JBSEAM-3652
Project: Seam
Issue Type: Bug
Affects Versions: 2.0.2.SP1, 2.0.3.CR1, 2.1.0.GA
Environment: WebSphere v6.1.0.17 in POJO Mode
Reporter: Denis Forveille
Assignee: Dan Allen
Priority: Blocker
Fix For: 2.1.1.CR1
Attachments: Test3652.java, Test3652Conv.java, testJBSEAM3652.xhtml, traces.txt
This bug is very similar to the JBSEAM-3295 bug, but for "Page Scope"
components this time
Under stress, we have random NPE, "conversation expired" and other strange
eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy
to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a
classic "list entities/showDetail" scheme. The controleur that manages the list
is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one
etc... without waiting for the detail view to show up, we have two concurrent request
addressed to the same Page Scope component (Verified by putting traces in the
BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two
concurrent thread running: the current thread + another one currently "using"
the component
The counter will be decrease for the first time on line 82, then a second time on line
129 and so, disinjection will occur on line 134. This occurs while there is another thread
"using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one
"concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page
acces the same page scope component concurrently (I thought seam was taking care of this
and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent
"user" of the component exits the interceptor and not when each request
"eixts" the interceptor?
--
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5758
days inactive
5926
days old
13 comments
4 participants
participants (4)
-
Dan Allen (JIRA) -
Denis Forveille (JIRA)
-
Pete Muir (JIRA)
-
Shane Bryzak (JIRA)