Memory leak in UIDGenerator
---------------------------
Key: AXIOM-390
URL: https://issues.apache.org/jira/browse/AXIOM-390
Project: Axiom
Issue Type: Bug
Components: API
Affects Versions: 1.2.12
Environment: Tomcat 7.0.21, Axis2 1.6.1 with Axiom 1.2.12
Reporter: Detlef Günther
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);
}
...
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