title: JVM - What does "JOURNAL_FLUSHER" warning mean?
body: <p>I am running an application and after a while, the logs would display </p>
  
  <pre><code>15:31:41 [WARN] [15:31:41.002] [JOURNAL_FLUSHER] WARNING Journal flush operation took 3,678ms last 8 cycles average is 459ms
  15:33:53 [WARN] [15:33:43.878] [JOURNAL_FLUSHER] WARNING Journal flush operation took 4,872ms last 8 cycles average is 609ms
  15:34:48 [WARN] [15:34:40.084] [JOURNAL_FLUSHER] WARNING Journal flush operation took 4,941ms last 8 cycles average is 772ms
  15:35:13 [WARN] [15:35:13.051] [JOURNAL_FLUSHER] WARNING Journal flush operation took 12,299ms last 8 cycles average is 2,306ms
  15:38:19 [WARN] [15:38:13.718] [JOURNAL_FLUSHER] WARNING Journal flush operation took 2,366ms last 8 cycles average is 295ms
  15:39:01 [WARN] [15:38:53.897] [JOURNAL_FLUSHER] WARNING Journal flush operation took 8,651ms last 8 cycles average is 1,377ms
  </code></pre>
  
  <p>What exactly does this mean? After a while, the application grinds to a halt and throws a heap space error. Does this mean I have to increase the heap size or the permgen size? My application runs well on another computer, however, on this one it will get exponentially slower. I am not really asking how to fix this problem, but what this warning means. </p>