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From Gary Gregory <garydgreg...@gmail.com>
Subject Re: Log4j2 RollingFileAppender deadlock issue
Date Sat, 04 Jul 2015 07:45:42 GMT
So the simplest thing to so would for PatternConverter to implement a
stop() method to clear the ThreadLocal (extending AbstractLifeCycle might
be too heavy for now)

The tricky part is how to connect the dots from an appender stopping all
the way to the PatternConverter. Unless we go the route of the registry.

Gary

On Thu, Jul 2, 2015 at 10:34 AM, Gary Gregory <garydgregory@gmail.com>
wrote:

> Or the org.apache.logging.log4j.core.pattern.AbstractPatternConverter
> could extend org.apache.logging.log4j.core.AbstractLifeCycle and clearing
> the ThreadLocale would be done in stop(). The stop would have to be called
> at the right time of course.
>
> Gary
>
> On Thu, Jul 2, 2015 at 6:18 AM, Remko Popma <remko.popma@gmail.com> wrote:
>
>> Yes, that could still work: We could use a ThreadLocal containing a
>> custom class which holds the lastTimestamp, cachedDateString as well as a
>> SimpleDateFormat instance.
>>
>> As Jess pointed out, we would also need a way to clear the ThreadLocal
>> when the LoggerContext is stopped (to prevent memory leaks in web apps).
>> This may be the third usage of ThreadLocals in log4j2 now, so it may be
>> worth creating a reusable mechanism for this.
>> One idea would be to have a ThreadLocal registry in the LoggerContext,
>> where the LoggerContext is responsible for cleaning up all registered
>> ThreadLocals in its stop() method.
>>
>> Thoughts?
>>
>> Remko..
>> Sent from my iPhone
>>
>> On 2015/07/02, at 22:00, Gary Gregory <garydgregory@gmail.com> wrote:
>>
>> What about storing a SimpleDateFormat in a ThreadLocal?
>>
>> But, more importantly and aside from SimpleDateFormat not being
>> thread-safe [1], I thought we used synchronized to keep
>> the lastTimestamp and cachedDateString ivar perfectly matched up:
>>
>>     public void format(final LogEvent event, final StringBuilder output) {
>>         final long timestamp = event.getTimeMillis();
>>
>>         synchronized (this) {
>>             if (timestamp != lastTimestamp) {
>>                 lastTimestamp = timestamp;
>>                 cachedDateString = formatter.format(timestamp);
>>             }
>>         }
>>         output.append(cachedDateString);
>>     }
>>
>> But #2, lastTimestamp and cachedDateString are not volatile, so do we
>> really care?
>>
>> Gary
>>
>> [1] Javadoc: Date formats are not synchronized.
>>  * It is recommended to create separate format instances for each thread.
>>  * If multiple threads access a format concurrently, it must be
>> synchronized
>>  * externally.
>>
>>
>> On Thu, Jul 2, 2015 at 5:34 AM, Ralph Goers <ralph.goers@dslextreme.com>
>> wrote:
>>
>>> 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 <garydgregory@gmail.com>
>>> *Date:* 2015-07-02 17:35
>>> *To:* Log4J Developers List <log4j-dev@logging.apache.org>
>>> *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 <garydgregory@gmail.com>
>>>>> *Date:* 2015-07-02 16:55
>>>>> *To:* Log4J Developers List <log4j-dev@logging.apache.org>
>>>>> *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 <log4j-dev@logging.apache.org>
>>>>>> *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 <garydgregory@gmail.com>
>>>>>> *Date:* 2015-07-02 15:57
>>>>>> *To:* Log4J Developers List <log4j-dev@logging.apache.org>
>>>>>> *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
>>>>>> <http://www.manning.com/bauer3/>
>>>>>> JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
>>>>>> Spring Batch in Action <http://www.manning.com/templier/>
>>>>>> Blog: http://garygregory.wordpress.com
>>>>>> Home: http://garygregory.com/
>>>>>> Tweet! http://twitter.com/GaryGregory
>>>>>>  [image: 提示图标] 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(07-02-13-34-56).jpg(1M) 极速下载
>>>>>> <http://preview.mail.163.com/xdownload?filename=Catch%2807-02-13-34-56%29.jpg&mid=xtbBEQQrgVD%2BdaYDbgAAsv&part=3&sign=455fc16698556220f55a79d0de214c25&time=1435824425&uid=bit1129%40163.com>
>>>>>> 在线预览
>>>>>> <http://preview.mail.163.com/preview?mid=xtbBEQQrgVD%2BdaYDbgAAsv&part=3&sign=455fc16698556220f55a79d0de214c25&time=1435824425&uid=bit1129%40163.com>
>>>>>>
>>>>>>
>>>>>>
>>>>>> ---------------------------------------------------------------------
>>>>>> To unsubscribe, e-mail: log4j-dev-unsubscribe@logging.apache.org
>>>>>> For additional commands, e-mail: log4j-dev-help@logging.apache.org
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> E-Mail: garydgregory@gmail.com | ggregory@apache.org
>>>>> Java Persistence with Hibernate, Second Edition
>>>>> <http://www.manning.com/bauer3/>
>>>>> JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
>>>>> Spring Batch in Action <http://www.manning.com/templier/>
>>>>> Blog: http://garygregory.wordpress.com
>>>>> Home: http://garygregory.com/
>>>>> Tweet! http://twitter.com/GaryGregory
>>>>>  [image: 提示图标] 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(07-02-16-25-44).jpg(1M) 极速下载
>>>>> <http://preview.mail.163.com/xdownload?filename=Catch%2807-02-13-3%2807-02-16-25-44%29.jpg&mid=1tbiqxUrgVUL5JhKtgAAsK&part=3&sign=23395f9d62f60d2dbad11e39911e54c8&time=1435827868&uid=bit1129%40163.com>
>>>>> 在线预览
>>>>> <http://preview.mail.163.com/preview?mid=1tbiqxUrgVUL5JhKtgAAsK&part=3&sign=23395f9d62f60d2dbad11e39911e54c8&time=1435827868&uid=bit1129%40163.com>
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> E-Mail: garydgregory@gmail.com | ggregory@apache.org
>>>> Java Persistence with Hibernate, Second Edition
>>>> <http://www.manning.com/bauer3/>
>>>> JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
>>>> Spring Batch in Action <http://www.manning.com/templier/>
>>>> 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
>>> <http://www.manning.com/bauer3/>
>>> JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
>>> Spring Batch in Action <http://www.manning.com/templier/>
>>> Blog: http://garygregory.wordpress.com
>>> Home: http://garygregory.com/
>>> Tweet! http://twitter.com/GaryGregory
>>>  [image: 提示图标] 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
>>> <http://preview.mail.163.com/xdownload?filename=Catch%2807-02-13-3%2807-02-17-13-37%29.jpg&mid=1tbiqwYrgVUL5JjPdwAAsd&part=3&sign=9f422144b7596ead1d7a91185a34196d&time=1435829869&uid=bit1129%40163.com>
>>> 在线预览
>>> <http://preview.mail.163.com/preview?mid=1tbiqwYrgVUL5JjPdwAAsd&part=3&sign=9f422144b7596ead1d7a91185a34196d&time=1435829869&uid=bit1129%40163.com>
>>>
>>>
>>
>>
>> --
>> E-Mail: garydgregory@gmail.com | ggregory@apache.org
>> Java Persistence with Hibernate, Second Edition
>> <http://www.manning.com/bauer3/>
>> JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
>> Spring Batch in Action <http://www.manning.com/templier/>
>> 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
> <http://www.manning.com/bauer3/>
> JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
> Spring Batch in Action <http://www.manning.com/templier/>
> 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
<http://www.manning.com/bauer3/>
JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
Spring Batch in Action <http://www.manning.com/templier/>
Blog: http://garygregory.wordpress.com
Home: http://garygregory.com/
Tweet! http://twitter.com/GaryGregory

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