Java Heap Retention in java.io.DeleteOnExitHook

Solution Verified - Updated

Environment

  • Red Hat JBoss Enterprise Application Platform
  • Red Hat JBoss Web Server (Tomcat)

Issue

Experiencing memory issues with java.io.DeleteOnExitHook. It is consistently a high consumer of memory in our heap.

Resolution

Minimize calls to File.deleteOnExit. Delete files (File.delete) once you are done with them in your application.

Root Cause

  • When you call File.deleteOnExit, the File's path is stored in the DeleteOnExitHook until the JVM terminates/exits. Here is example output from Eclipse Memory Analyzer's Dominator Tree:
Class Name                                               | Shallow Heap | Retained Heap | Percentage
-----------------------------------------------------------------------------------------------------
class java.io.DeleteOnExitHook @ 0x1c93f6dd0 System Class|            8 | 1,239,630,608 |     71.29%
'- java.util.LinkedHashSet @ 0x1c9653a20                 |           16 | 1,239,630,600 |     71.29%
   '- java.util.LinkedHashMap @ 0x1c9653a30              |           56 | 1,239,630,584 |     71.29%
      |- java.util.HashMap$Node[16777216] @ 0x29775f350  |   67,108,880 |    67,108,880 |      3.86%
      |- java.util.LinkedHashMap$Entry @ 0x1d16c41b0     |           40 |           184 |      0.00%
      |- java.util.LinkedHashMap$Entry @ 0x1d16c4318     |           40 |           184 |      0.00%
      |- java.util.LinkedHashMap$Entry @ 0x1d16c45e0     |           40 |           184 |      0.00%
      |- java.util.LinkedHashMap$Entry @ 0x1d16c47f8     |           40 |           184 |      0.00%
     Total: 5 of 6,502,001 entries; 6,501,996 more
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