RFR: 7164841: Improvements to the GC log file rotation

[Tao Mao]

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.

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().

(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.

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?

4. Will you write jtreg tests for this functionality? It looks possible 
to write some tests, at least checking the format of log names.

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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