Limitations

Log Files Rotation

In order for gcpc to receive GC log files continuously and without gaps, they have to be rotating. You can control such behavior with -XX:+UseGCLogFileRotation and -XX:NumberOfGCLogFiles=N, where N is a max number of files. The example of directory structure with rotating logs:

$ ls -la
total 604
drwxr-xr-x 2 gcs gcs   4096 Apr 16 15:35 .
drwxr-xr-x 3 gcs gcs   4096 Apr  4 22:43 ..
-rw-rw-r-- 1 gcs gcs 131290 Apr 12 22:12 gc.log.0
-rw-rw-r-- 1 gcs gcs 131512 Apr 14 09:59 gc.log.1
-rw-rw-r-- 1 gcs gcs 131180 Apr 14 10:00 gc.log.2
-rw-rw-r-- 1 gcs gcs  88910 Apr 16 15:36 gc.log.3.current

In that case gcpc will known that gc.log.3.current file is currently being written, while gc.log.0, gc.log.1 and gc.log.2 can be already uploaded and processed.

Datestamps Required

Yes, basically GCPlot Connector ecosystem can't work with GC log files with timestamps-only, which are reset to zero with every new file. In that case it's extremely hard to match each log with each other and show you a continuous and correct report.

If you have such problem, just add -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps flags to your JVM on startup.

Here is an example of log file with timestamps-only:

0.000: [GC [1 CMS-initial-mark: 0K(12288K)] 281K(16320K), 0.0053399 secs]
0.006: [CMS-concurrent-mark-start]
0.057: [CMS-concurrent-mark: 0.051/0.051 secs]
0.057: [CMS-concurrent-preclean-start]
0.057: [CMS-concurrent-preclean: 0.000/0.000 secs]

And this is with datestamps presented as well:

2015-07-02T20:53:00.436+0200: 0.260: [GC (Allocation Failure) [PSYoungGen: 24571K->4081K(28672K)] 24571K->22186K(94208K), 0.0199218 secs] [Times: user=0.02 sys=0.02, real=0.02 secs]
2015-07-03T06:58:33.016+0200: 75416.800: [GC (GCLocker Initiated GC) [PSYoungGen: 616448K->6515K(650240K)] 1041014K->431081K(1705472K), 0.0239463 secs] [Times: user=0.09 sys=0.00, real=0.03 secs] 
2015-07-03T09:35:15.452+0200: 84819.235: [GC (Last ditch collection) [PSYoungGen: 0K->0K(678400K)] 575536K->575536K(2076672K), 0.0193629 secs] [Times: user=0.06 sys=0.01, real=0.01 secs]

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