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ConcurrentModificationException ???? Linux

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SkipDever

ConcurrentModificationException ???? Linux

I am frequently getting a java.util.ConcurrentModificationException from:

java.util.LinkedList$ListItr.next()
org.ofbiz.widget.form.ModelForm.renderHeaderRow(ModelForm.java:1074)
....

I only get this error using a Centos server. Another server running Windows
has no similiar complaint.

I looked at the code and cannot possibly see how a single copy of the
ModelForm object could be used in multiple threads? The list causing the
grief is the fieldList and a new one is instantiated each time the modelform
is created, i.e. it is not static.

This server runs for a few days before this error occurs.

Note that this exception is from 9.0 based ofbiz code. I did a comparison
of the 9x code and the 10.x ModelForm.java code and see that this stuff has
been almost completely rewritten.

Anyone have any insite?

Skip

Adrian Crum-3

Re: ConcurrentModificationException ???? Linux

Skip,

The widget models are kept in a memory cache and the model instances are
shared among threads. There were a number of thread-safe issues in the
9.x widget models. Some have been fixed, others have Jira issues and
still need to be fixed. It is not uncommon for thread-safe bugs to
appear sporadically - since the bug is timing-dependent. If you have a
specific revision number, I might be able to suggest a fix.

-Adrian

On 5/25/2011 6:19 PM, SkipDever wrote:

>
> I am frequently getting a java.util.ConcurrentModificationException from:
>
> java.util.LinkedList$ListItr.next()
> org.ofbiz.widget.form.ModelForm.renderHeaderRow(ModelForm.java:1074)
> ....
>
> I only get this error using a Centos server. Another server running Windows
> has no similiar complaint.
>
> I looked at the code and cannot possibly see how a single copy of the
> ModelForm object could be used in multiple threads? The list causing the
> grief is the fieldList and a new one is instantiated each time the modelform
> is created, i.e. it is not static.
>
> This server runs for a few days before this error occurs.
>
> Note that this exception is from 9.0 based ofbiz code. I did a comparison
> of the 9x code and the 10.x ModelForm.java code and see that this stuff has
> been almost completely rewritten.
>
> Anyone have any insite?
>
> Skip
>

SkipDever

RE: ConcurrentModificationException ???? Linux

Adrian

Thanks, version looks like 9.04

Skip

-----Original Message-----
From: Adrian Crum [mailto:[hidden email]]
Sent: Wednesday, May 25, 2011 3:14 PM
To: [hidden email]
Subject: Re: ConcurrentModificationException ???? Linux

Skip,

The widget models are kept in a memory cache and the model instances are
shared among threads. There were a number of thread-safe issues in the
9.x widget models. Some have been fixed, others have Jira issues and
still need to be fixed. It is not uncommon for thread-safe bugs to
appear sporadically - since the bug is timing-dependent. If you have a
specific revision number, I might be able to suggest a fix.

-Adrian

On 5/25/2011 6:19 PM, SkipDever wrote:
>
> I am frequently getting a java.util.ConcurrentModificationException from:
>
> java.util.LinkedList$ListItr.next()
> org.ofbiz.widget.form.ModelForm.renderHeaderRow(ModelForm.java:1074)
> ....
>
> I only get this error using a Centos server. Another server running
Windows
> has no similiar complaint.
>
> I looked at the code and cannot possibly see how a single copy of the
> ModelForm object could be used in multiple threads? The list causing the
> grief is the fieldList and a new one is instantiated each time the
modelform
> is created, i.e. it is not static.
>
> This server runs for a few days before this error occurs.
>
> Note that this exception is from 9.0 based ofbiz code. I did a comparison
> of the 9x code and the 10.x ModelForm.java code and see that this stuff
has
> been almost completely rewritten.
>
> Anyone have any insite?
>
> Skip
>

SkipDever

RE: ConcurrentModificationException ???? Linux

In reply to this post by Adrian Crum-3

I am wondering if I can just move all the
/framework/widget/src/org/ofbiz/widget/form*.java from 10.04 into my build
and have some chance of it building? Fortunately, I have not modified any
of this code.

Skip

-----Original Message-----
From: Adrian Crum [mailto:[hidden email]]
Sent: Wednesday, May 25, 2011 3:14 PM
To: [hidden email]
Subject: Re: ConcurrentModificationException ???? Linux

Skip,

The widget models are kept in a memory cache and the model instances are
shared among threads. There were a number of thread-safe issues in the
9.x widget models. Some have been fixed, others have Jira issues and
still need to be fixed. It is not uncommon for thread-safe bugs to
appear sporadically - since the bug is timing-dependent. If you have a
specific revision number, I might be able to suggest a fix.

-Adrian

On 5/25/2011 6:19 PM, SkipDever wrote:
>
> I am frequently getting a java.util.ConcurrentModificationException from:
>
> java.util.LinkedList$ListItr.next()
> org.ofbiz.widget.form.ModelForm.renderHeaderRow(ModelForm.java:1074)
> ....
>
> I only get this error using a Centos server. Another server running
Windows
> has no similiar complaint.
>
> I looked at the code and cannot possibly see how a single copy of the
> ModelForm object could be used in multiple threads? The list causing the
> grief is the fieldList and a new one is instantiated each time the
modelform
> is created, i.e. it is not static.
>
> This server runs for a few days before this error occurs.
>
> Note that this exception is from 9.0 based ofbiz code. I did a comparison
> of the 9x code and the 10.x ModelForm.java code and see that this stuff
has
> been almost completely rewritten.
>
> Anyone have any insite?
>
> Skip
>

Adrian Crum-3

Re: ConcurrentModificationException ???? Linux

You might have better luck replacing the entire widget component.

-Adrian

On 5/26/2011 12:47 AM, SkipDever wrote:

> I am wondering if I can just move all the
> /framework/widget/src/org/ofbiz/widget/form*.java from 10.04 into my build
> and have some chance of it building? Fortunately, I have not modified any
> of this code.
>
> Skip
>
> -----Original Message-----
> From: Adrian Crum [mailto:[hidden email]]
> Sent: Wednesday, May 25, 2011 3:14 PM
> To: [hidden email]
> Subject: Re: ConcurrentModificationException ???? Linux
>
>
> Skip,
>
> The widget models are kept in a memory cache and the model instances are
> shared among threads. There were a number of thread-safe issues in the
> 9.x widget models. Some have been fixed, others have Jira issues and
> still need to be fixed. It is not uncommon for thread-safe bugs to
> appear sporadically - since the bug is timing-dependent. If you have a
> specific revision number, I might be able to suggest a fix.
>
> -Adrian
>
> On 5/25/2011 6:19 PM, SkipDever wrote:
>> I am frequently getting a java.util.ConcurrentModificationException from:
>>
>> java.util.LinkedList$ListItr.next()
>> org.ofbiz.widget.form.ModelForm.renderHeaderRow(ModelForm.java:1074)
>> ....
>>
>> I only get this error using a Centos server. Another server running
> Windows
>> has no similiar complaint.
>>
>> I looked at the code and cannot possibly see how a single copy of the
>> ModelForm object could be used in multiple threads? The list causing the
>> grief is the fieldList and a new one is instantiated each time the
> modelform
>> is created, i.e. it is not static.
>>
>> This server runs for a few days before this error occurs.
>>
>> Note that this exception is from 9.0 based ofbiz code. I did a comparison
>> of the 9x code and the 10.x ModelForm.java code and see that this stuff
> has
>> been almost completely rewritten.
>>
>> Anyone have any insite?
>>
>> Skip
>>

SkipDever

RE: ConcurrentModificationException ???? Linux

Thanks Adrian, I'll give that a go

-----Original Message-----
From: Adrian Crum [mailto:[hidden email]]
Sent: Wednesday, May 25, 2011 4:48 PM
To: [hidden email]
Subject: Re: ConcurrentModificationException ???? Linux

You might have better luck replacing the entire widget component.

-Adrian

On 5/26/2011 12:47 AM, SkipDever wrote:

comparison
>> of the 9x code and the 10.x ModelForm.java code and see that this stuff
> has
>> been almost completely rewritten.
>>
>> Anyone have any insite?
>>
>> Skip
>>

SkipDever

RE: ConcurrentModificationException ???? Linux

In reply to this post by SkipDever

Adrian

Turns out that using the entire widget component is not an option. There
are references to ../../common.xml and ../../macros.xml which references
<pathelement
location="${ofbiz.home.dir}/framework/base/lib/commons/commons-cli-1.0.jar"/
>
<pathelement
location="${ofbiz.home.dir}/framework/base/lib/scripting/antlr-2.7.6.jar"/>
<pathelement
location="${ofbiz.home.dir}/framework/base/lib/scripting/asm-3.2.jar"/>
<pathelement
location="${ofbiz.home.dir}/framework/base/lib/scripting/groovy-1.7-rc-2.jar
"/>

and so on.

I can probably clean up that build.xml file, but not sure if it's wasted
effort or not.

In the mean time, I am considering removing the Iterator references and
replacing them with foreach. The Iterator seems to be where the problems
are.

Any advice as to the shortest route to a fix? Moving to 10.04 is not
currently an option as I have made hundreds of modifications to the ofbiz
core code, all of which would have to be remade and tested.

Skip

-----Original Message-----
From: Adrian Crum [mailto:[hidden email]]
Sent: Wednesday, May 25, 2011 4:48 PM
To: [hidden email]
Subject: Re: ConcurrentModificationException ???? Linux

You might have better luck replacing the entire widget component.

-Adrian

On 5/26/2011 12:47 AM, SkipDever wrote:
> I am wondering if I can just move all the
> /framework/widget/src/org/ofbiz/widget/form*.java from 10.04 into my build
> and have some chance of it building? Fortunately, I have not modified any
> of this code.
>
> Skip
>

Adrian Crum-3

Re: ConcurrentModificationException ???? Linux

According to your previous message, it appears a list is being modified
by more than one thread. Something needs to be done to guard that list
so that only one thread can modify it at a time. If you could give me a
revision number (not a release number) I might be able to provide more
details.

-Adrian

On 5/27/2011 6:46 PM, SkipDever wrote:

> Adrian
>
> Turns out that using the entire widget component is not an option. There
> are references to ../../common.xml and ../../macros.xml which references
> <pathelement
> location="${ofbiz.home.dir}/framework/base/lib/commons/commons-cli-1.0.jar"/
> <pathelement
> location="${ofbiz.home.dir}/framework/base/lib/scripting/antlr-2.7.6.jar"/>
> <pathelement
> location="${ofbiz.home.dir}/framework/base/lib/scripting/asm-3.2.jar"/>
> <pathelement
> location="${ofbiz.home.dir}/framework/base/lib/scripting/groovy-1.7-rc-2.jar
> "/>
>
> and so on.
>
> I can probably clean up that build.xml file, but not sure if it's wasted
> effort or not.
>
> In the mean time, I am considering removing the Iterator references and
> replacing them with foreach. The Iterator seems to be where the problems
> are.
>
> Any advice as to the shortest route to a fix? Moving to 10.04 is not
> currently an option as I have made hundreds of modifications to the ofbiz
> core code, all of which would have to be remade and tested.
>
> Skip
>
> -----Original Message-----
> From: Adrian Crum [mailto:[hidden email]]
> Sent: Wednesday, May 25, 2011 4:48 PM
> To: [hidden email]
> Subject: Re: ConcurrentModificationException ???? Linux
>
>
> You might have better luck replacing the entire widget component.
>
> -Adrian
>
> On 5/26/2011 12:47 AM, SkipDever wrote:
>> I am wondering if I can just move all the
>> /framework/widget/src/org/ofbiz/widget/form*.java from 10.04 into my build
>> and have some chance of it building? Fortunately, I have not modified any
>> of this code.
>>
>> Skip
>>