[AXIOM-390] Memory leak in UIDGenerator

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Invalid
• Affects Version/s: 1.2.12
• Component/s: API
• Environment: Tomcat 7.0.21, Axis2 1.6.1 with Axiom 1.2.12
• Assignee: Unassigned
• Reporter: Detlef Günther
• Created: 16/Sep/11 06:48
• Updated: 18/Sep/11 19:10
• Resolved: 18/Sep/11 19:10

Description

Shutting down tomcat produces a list of error messages for each request of a web service:

16.09.2011 08:36:16 org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SCHWERWIEGEND: The web application [/datatransfer] created a ThreadLocal with key of type [org.apache.axiom.util.UIDGenerator$1] (value [org.apache.axiom.util.UIDGenerator$1@252a78ee]) and a value of type [long[]] (value [[J@7696452]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.

Problem seems to be ThreadLocal, which cannot bee cleaned up after processing the request. Eliminating ThreadLocal solves the problem:

public final class UIDGenerator {
// private static final long startTimeXorOperand;
private static final long threadIdXorOperand;
private static final long seqXorOperand;

static

{ Random rand = new Random(); threadIdXorOperand = rand.nextLong(); // startTimeXorOperand = rand.nextLong(); seqXorOperand = rand.nextLong(); }

private final static AtomicLong seqValue = new AtomicLong(0);

private UIDGenerator() {
}

private static void writeReverseLongHex(long value, StringBuilder buffer) {
for (int i = 0; i < 64; i += 4)

{ int n = (int) (value >> i) & 0xF; buffer.append((char) (n < 10 ? '0' + n : 'a' + n - 10)); }

}

/**

• Generate a unique ID as hex value and add it to the given buffer. Note that
• with respect to the triplet, the order of nibbles is reversed, i.e. the
• least significant nibble of the sequence is written first. This makes
• comparing two IDs for equality more efficient.
• @param buffer
  */
  private static void generateHex(StringBuilder buffer) { writeReverseLongHex(seqValue.incrementAndGet() ^ seqXorOperand, buffer); writeReverseLongHex(Thread.currentThread().getId() ^ threadIdXorOperand, buffer); }

...