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From Ralph Goers <ralph.go...@dslextreme.com>
Subject Re: Log4j2 RollingFileAppender deadlock issue
Date Thu, 02 Jul 2015 12:34:46 GMT
The date pattern converter will be locking because it uses SimpleDateFormat to format the date.
 This can be changed in Java 8, but the only alternative until then is to use the Joda Time
library and we have been reluctant to be reliant on third party libraries for such core components.


Sent from my iPad

> On Jul 2, 2015, at 3:44 AM, "bit1129@163.com" <bit1129@163.com> wrote:
> 
> Thanks Gary.
> 
> Limit number of threads can help alleviate the problem, but can't make it disappear.
Especially when it happens during midnight when the workload will far below the average than
the day,but we have no such problems happens during day.
> 
> I didn't dive into the code to see what it is doing within the synchronized block,which
takes so much time.
> 
> I still think there should be something that is problematic in log4j.
> 
> bit1129@163.com
>  
> From: Gary Gregory
> Date: 2015-07-02 17:35
> To: Log4J Developers List
> Subject: Re: Re: Log4j2 RollingFileAppender deadlock issue
> and let's be clear, unlike the subject of this thread, there is no deadlock here, at
least not in the thread dump you shared; the application appears hung but is in fact slowed
down to a crawl. IMO that is ;-)
> 
> Gary
> 
>> On Thu, Jul 2, 2015 at 2:34 AM, Gary Gregory <garydgregory@gmail.com> wrote:
>> The more threads you run to service additional requests is making the problem worse
IMO. This likely causes swapping out the wazoo. I would bind the thread pool to try to avoid

>> 
>> 
>> in service.
>> 
>> Gary
>> 
>>> On Thu, Jul 2, 2015 at 2:25 AM, bit1129@163.com <bit1129@163.com> wrote:
>> 
>>> Thanks Gary. 
>>> So, it's abnormal for so many (2000+)threads to wait for the lock. The workload
of our application is not very high. So, It is kind of too long for the <0x0000000772fe2860>
owner thread to unlock it.
>>> 
>>> 6k threads in total is abnormal, as we are using *unlimited* thread pool in our
code to do HTTP requests to other services when responding user's request. Since the threads
of the thread pool is waiting for the lock, so the thread pool has to kick off new threads
when we throw tasks to it.
>>> 
>>> 
>>> 
>>> 
>>> bit1129@163.com
>>>  
>>> From: Gary Gregory
>>> Date: 2015-07-02 16:55
>>> To: Log4J Developers List
>>> Subject: Re: Re: Log4j2 RollingFileAppender deadlock issue
>>> Wow, > 6k threads? Is that normal for your application?
>>> 
>>> I do see two locks on two DatePatternConverter instances, and both are working:
>>> 
>>> "resin-port-7280-7309" daemon prio=10 tid=0x00002ba94d16e000 nid=0x69e6 runnable
[0x00002bab56be5000]
>>>    java.lang.Thread.State: RUNNABLE
>>> 	at java.lang.AbstractStringBuilder.<init>(AbstractStringBuilder.java:64)
>>> 	at java.lang.StringBuffer.<init>(StringBuffer.java:96)
>>> 	at java.text.Format.format(Format.java:157)
>>> 	at org.apache.logging.log4j.core.pattern.DatePatternConverter$PatternFormatter.format(DatePatternConverter.java:50)
>>> 	at org.apache.logging.log4j.core.pattern.DatePatternConverter.format(DatePatternConverter.java:251)
>>> 	- locked <0x00000007a2cecaa0> (a org.apache.logging.log4j.core.pattern.DatePatternConverter)
>>> 	at org.apache.logging.log4j.core.pattern.PatternFormatter.format(PatternFormatter.java:36)
>>> 	at org.apache.logging.log4j.core.layout.PatternLayout.toSerializable(PatternLayout.java:189)
>>> ...
>>> "DataChannel-1-thread-802" prio=10 tid=0x00002ba8c0022800 nid=0x1fbc runnable
[0x00002ba983230000]
>>>    java.lang.Thread.State: RUNNABLE
>>> 	at java.lang.StringBuffer.toString(StringBuffer.java:561)
>>> 	- locked <0x0000000772fe2860> (a java.lang.StringBuffer)
>>> 	at java.text.Format.format(Format.java:157)
>>> 	at org.apache.logging.log4j.core.pattern.DatePatternConverter$PatternFormatter.format(DatePatternConverter.java:50)
>>> 	at org.apache.logging.log4j.core.pattern.DatePatternConverter.format(DatePatternConverter.java:251)
>>> 	- locked <0x00000007a2cecc08> (a org.apache.logging.log4j.core.pattern.DatePatternConverter)
>>> 	at org.apache.logging.log4j.core.pattern.PatternFormatter.format(PatternFormatter.java:36)
>>> 	at org.apache.logging.log4j.core.layout.PatternLayout.toSerializable(PatternLayout.java:189)
>>> 
>>> Lots (> 2k) of threads are waiting on these two locks.
>>> 
>>> So that is all 'normal' in the sense that I do not see a deadlock, this is more
of a starvation scenario.
>>> 
>>> --
>>> 
>>> Tangent for us Log4j devs:
>>> 
>>> It sure is lame that java.text.Format still uses a StringBuffer internally instead
of a StringBuilder, which would be faster.
>>> 
>>> Looking at reusing Commons Lang's FastDateParser would not help since it does
not add StringBuilder version of the StringBuffer APIs.
>>> 
>>> Gary
>>> 
>>> 
>>>> On Thu, Jul 2, 2015 at 1:26 AM, bit1129@163.com <bit1129@163.com> wrote:
>>>> Sorry, looks that I forgot to attach the thread dump file. 
>>>> 
>>>> bit1129@163.com
>>>>  
>>>> From: bit1129@163.com
>>>> Date: 2015-07-02 16:25
>>>> To: log4j-dev
>>>> Subject: Re: Re: Log4j2 RollingFileAppender deadlock issue
>>>> Thanks Gary for the reply.
>>>> The log related stuff is:
>>>> 
>>>> <log4j2.version>2.0.2</log4j2.version> 
>>>> <log4j.version>1.2.16</log4j.version>
>>>> <slf4j.version>1.7.7</slf4j.version>
>>>> 
>>>> I have the thread dump in question ,and attach it in the attachment.
>>>> 
>>>> Thanks you!
>>>> 
>>>> bit1129@163.com
>>>>  
>>>> From: Gary Gregory
>>>> Date: 2015-07-02 15:57
>>>> To: Log4J Developers List
>>>> Subject: Re: Log4j2 RollingFileAppender deadlock issue
>>>> Hello,
>>>> 
>>>> What version of Log4j are you using?
>>>> 
>>>> Can you post the whole thread dump? You can capture it from VisualVM (jvisualvm)
which ships with the JDK).
>>>> 
>>>> Gary
>>>> 
>>>>> On Wed, Jul 1, 2015 at 10:36 PM, bit1129@163.com <bit1129@163.com>
wrote:
>>>>> 
>>>>> Hi,log4j developers,
>>>>> 
>>>>> I am using log4j2 to do log. Recently I have encountered an RollingFileAppender
deadlock issue from time to time which happens around 12:00 am ~03:00am. 
>>>>> When I dump the thread, there are lots of BLOCKED threads that waiting
for the lock 0x00000007a2cecaa0.
>>>>> 
>>>>> Following is my log4j configuration in log4j2.xml:
>>>>> 
>>>>> <RollingFile name="rolling" fileName="/data/logs/app/server.log" filePattern="/data/logs/app/server.log.%d{yyyy-MM-dd}">

>>>>> <PatternLayout pattern="[%-5level] [%d{yyyy-MM-dd HH:mm:ss}] [%C{1}:%M:%L]
%m%n" /> 
>>>>> <Policies> 
>>>>> <TimeBasedTriggeringPolicy /> 
>>>>> </Policies> 
>>>>> <DefaultRolloverStrategy max="30"/> 
>>>>> </RollingFile>
>>>>> 
>>>>> Is this a bug or there is some misconfiguration in my configuration.
Is there a way that I can work around this? It happens in our production environment.
>>>>> 
>>>>> <Catch(07-02-13-3(07-02-17-52-37).jpg>
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> bit1129@163.com
>>>> 
>>>> 
>>>> 
>>>> -- 
>>>> E-Mail: garydgregory@gmail.com | ggregory@apache.org 
>>>> Java Persistence with Hibernate, Second Edition
>>>> JUnit in Action, Second Edition
>>>> Spring Batch in Action
>>>> Blog: http://garygregory.wordpress.com 
>>>> Home: http://garygregory.com/
>>>> Tweet! http://twitter.com/GaryGregory
>>>>  邮件带有附件预览链接,若您转发或回复此邮件时不希望对方预览附件,建议您手动删除链接。
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>>>> 
>>>> 
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>>> 
>>> 
>>> 
>>> -- 
>>> E-Mail: garydgregory@gmail.com | ggregory@apache.org 
>>> Java Persistence with Hibernate, Second Edition
>>> JUnit in Action, Second Edition
>>> Spring Batch in Action
>>> Blog: http://garygregory.wordpress.com 
>>> Home: http://garygregory.com/
>>> Tweet! http://twitter.com/GaryGregory
>>>  邮件带有附件预览链接,若您转发或回复此邮件时不希望对方预览附件,建议您手动删除链接。
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>>> 极速下载 在线预览
>> 
>> 
>> 
>> 
>> -- 
>> E-Mail: garydgregory@gmail.com | ggregory@apache.org 
>> Java Persistence with Hibernate, Second Edition
>> JUnit in Action, Second Edition
>> Spring Batch in Action
>> Blog: http://garygregory.wordpress.com 
>> Home: http://garygregory.com/
>> Tweet! http://twitter.com/GaryGregory
> 
> 
> 
> -- 
> E-Mail: garydgregory@gmail.com | ggregory@apache.org 
> Java Persistence with Hibernate, Second Edition
> JUnit in Action, Second Edition
> Spring Batch in Action
> Blog: http://garygregory.wordpress.com 
> Home: http://garygregory.com/
> Tweet! http://twitter.com/GaryGregory
>  邮件带有附件预览链接,若您转发或回复此邮件时不希望对方预览附件,建议您手动删除链接。
> 共有 1 个附件
> Catch(07-02-13-3(07-02-17-13-37).jpg(1M)
> 极速下载 在线预览

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