RFR: 7164841: Improvements to the GC log file rotation

Yumin Qi yumin.qi at oracle.com
Mon Aug 26 10:01:40 PDT 2013


Bengt,

   Thanks for your comments.
   Yes, as you said, the purpose of rotating logs is primarily targeted 
for saving disk space. This bug is supplying  customers another option 
to prevent the previous gc logs from removed by restart app without 
making copy. Now with this pid and time stamp included in file name,  we 
have more options for users. It is up to user to make decision to or not 
to keep the logs. We cannot handle all the requests in JVM, but we can 
offer the choices for users I think. Any way, with either the previous 
rotating version, or the one I am working, the logs will not grow 
constantly without limit to blow storage out as long as users give 
enough attention.

   My concern is for no log rotation, should we still use time stamp in 
file name? I have one version for this, I hope get more comments for that.

   More comments are appreciated by sending to more wide audience, 
especially sustaining, they have more experience with customer request.

Thanks
Yumin



On 8/26/2013 4:47 AM, Bengt Rutisson wrote:
>
> Hi Yumin and Tao,
>
> I have not reviewed the code change but I have a comment inlined below.
>
> On 8/24/13 1:05 AM, Yumin Qi wrote:
>> Tao,
>>
>>   Thanks for your review.
>>
>> On 8/23/2013 3:33 PM, Tao Mao wrote:
>>> Hi,
>>>
>>> I reviewed most of the code and test-ran a build from it. It's a 
>>> very cool and important improvement.
>>>
>>> Thank you for putting together these on our wishlist for long.
>>>
>>> Below are some comments.
>>>
>>> 1. src/share/vm/runtime/arguments.cpp
>>>
>>> - 1853 "To enable GC log rotation, use -Xloggc:<filename> 
>>> -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=<num_of_files> 
>>> -XX:GCLogFileSize=<num_of_size>[k|K|m|M]\n"
>>> + 1853 "To enable GC log rotation, use -Xloggc:<filename> 
>>> -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=<num_of_files> 
>>> -XX:GCLogFileSize=<num_of_size>[k|K|m|M|g|G]\n"
>>>
>>> Please consider adding [g|G] to GCLogFileSize suggestion.
>>>
>>> I worked on a problem of enabling gc log limit over 2G 
>>> (JDK-7122222). So it seems that customers sometimes want gc logs to 
>>> be very large.
>>>
>> Sure, will add.
>>> 2. src/share/vm/runtime/arguments.hpp
>>>
>>> (1) with the current changeset, we only append date&time to 
>>> file_name w/ +UseGCLogFileRotation; if not, we won't have date&time 
>>> info.
>>>
>>> I think it would be useful to let both cases (w/ and w/o 
>>> UseGCLogFileRotation) have date&time in order to solve the 
>>> overwritten problem (e.g. JDK-8020667). In fact, having that, we 
>>> actually solve JDK-8020667.
>>>
>>> If you want to have that, basically you need to work on the 
>>> FileStream constructor methods fileStream().
>>>
>> I can change that, if no objection from others. This also will 
>> simplify the setting of file name here.
>
> I think appending a timestamp to the log file name is a nice idea, but 
> I think it is also a bit scary. There are users who restart their 
> applications regularly. With the suggested idea such users will now 
> risk filling up their disk space with log files. I imagine that that 
> will not be appreciated by everyone. Such a change should probably be 
> discussed more thoroughly than just in a review request.
>
> Thanks,
> Bengt
>
>
>>
>>> (2) Would it be better to rename method name reformat_filename() to 
>>> extend_filename()?
>>>
>>> (3) Typos and suggestion
>>> 537 // rotate file in names filename.0, filename.1, ..., 
>>> filename.<NumberOfGCLogFiles - 1>
>>> *=> extended_filename.0*
>>>
>>> 538 // filename contains pid and time when the fist file created. 
>>> The current filename is
>>> *=> *the*first *file created.
>>>
>>> 539 // gc_log_file_name + pid<pid> + 
>>> YYYY-MM-DD_HH-MM-SS.<i>.current, where i is current
>>> 540 // rotation file number. After it reaches max file size, the 
>>> file will be saved and
>>> 541 // renamed with .current removed from its tail.
>>>
>> Will change that.
>>> 3. For your point 5), I don't quite get it. In my test-run, I tried 
>>> to change file permission to unreadable and unwritable, but VM would 
>>> later change the permission back anyway.
>>>
>>> So could you bring up some use cases of that functionality to give 
>>> more details?
>>>
>> Changing file permission will not stop the file create, in this 
>> rotation, the file opened/saved/removed/renamed -> then repeat. What 
>> I have done is change the while directory to read only, then the 
>> create failed so rotation stopped.
>>
>>> 4. Will you write jtreg tests for this functionality? It looks 
>>> possible to write some tests, at least checking the format of log 
>>> names.
>>>
>> Good suggestion, I will add one.
>>
>>> Thanks.
>>> Tao
>>>
>>> On 8/23/13 7:53 AM, Yumin Qi wrote:
>>>> Could I get  a GC staff review the change? Need more reviewers to 
>>>> push this in.
>>>>
>>>> Thanks
>>>> Yumin
>>>>
>>>> On 8/21/2013 3:43 PM, Yumin Qi wrote:
>>>>> Hi, all
>>>>>
>>>>>   This is second version after feedback from first round.
>>>>>   The changes are:
>>>>>
>>>>>   1) file name will be based on gc log file name 
>>>>> (-Xloggc:filename), pid (process id) and time when the first 
>>>>> rotation file created:
>>>>>        <filename>-pid<pid>-YYYY-MM-DD_HH-MM-SS
>>>>>   2) If rotate in same file, file name is as in 1), if rotate in 
>>>>> multiple files, .<i> will append to above file name.
>>>>>   3) every time file rotated, file name and time when file created 
>>>>> will be logged to head/tail, this is same as first version.
>>>>>   4) current file has name 
>>>>> <filename>-pid<pid>-YYYY-MM-DD_HH-MM-SS.<i>.current
>>>>>        This is similar to first version.
>>>>>        By adapting such name format we will never loss logs in 
>>>>> case apps stops and restart, the log files will not be overwritten 
>>>>> since time stamp in file names.
>>>>>    5) If open file failed, turn off gc log rotation.
>>>>>         If due to some reason, file operation failed (such as 
>>>>> permission changed etc), with log file opened, logging still 
>>>>> works, but at
>>>>>         saving and renaming, the file operation will fail, this 
>>>>> will lead not all files saved.
>>>>>
>>>>> http://cr.openjdk.java.net/~minqi/7164841/webrev01
>>>>>
>>>>>      Tested with jtreg, JPRT.
>>>>>
>>>>> Thanks
>>>>> Yumin
>>>>>
>>>>> On 8/15/2013 8:35 AM, Yumin Qi wrote:
>>>>>> Hi,
>>>>>>
>>>>>>   Can I have your review for this small changes?
>>>>>> http://cr.openjdk.java.net/~minqi/7164841/webrev00/ 
>>>>>> <http://cr.openjdk.java.net/%7Eminqi/7164841/webrev00/>
>>>>>>
>>>>>>    This is for a enhancement to add head/tail message to the 
>>>>>> logging files to assist reading GC output.
>>>>>>    1. modified prompt message if invalid arguments used for log 
>>>>>> rotating;
>>>>>>    2. add time and file name message to log file head/tail.
>>>>>>    3. for easily identify which log file is current, use file 
>>>>>> name like <filename>.n.current, after it reaches maximum size, 
>>>>>> rename it to <filename>.n
>>>>>>         On Windows, there is no F_OK (existing test) definition, 
>>>>>> F_OK is defined as "0" and for _access of VC++, it just describes:
>>>>>>
>>>>>> modevalue
>>>>>>
>>>>>>
>>>>>>
>>>>>> Checks file for
>>>>>>
>>>>>> 00
>>>>>>
>>>>>>
>>>>>>
>>>>>> Existence only
>>>>>>
>>>>>> 02
>>>>>>
>>>>>>
>>>>>>
>>>>>> Write-only
>>>>>>
>>>>>> 04
>>>>>>
>>>>>>
>>>>>>
>>>>>> Read-only
>>>>>>
>>>>>> 06
>>>>>>
>>>>>>
>>>>>>
>>>>>> Read and write
>>>>>>
>>>>>>
>>>>>> http://msdn.microsoft.com/en-us/library/1w06ktdy.aspx
>>>>>> The definition are consistent with unistd.h.
>>>>>>
>>>>>>     Test: JPRT and jtreg.
>>>>>>
>>>>>>    Thanks
>>>>>>    Yumin
>>>>>
>>>>
>>
>>
>



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