/** Test where two locks are "passing over" to each other the lock ownership. */
@Test
public void twoLocksPassingOver() throws Exception {
final File lockFile = util.createTempFile();
final LockFile lf1 = new LockFile(lockFile, "lf1".getBytes());
final LockFile lf2 = new LockFile(lockFile, "lf2".getBytes());
try {
// lf1 will obtain lock, lf2 should fail
assertThat(lf1.lock(), is(true));
assertThat(lf2.lock(), is(false));
// verify who holds the lock
assertThat(lf1.readBytes(), equalTo(lf1.getPayload()));
// pass over the lock
lf1.release();
assertThat(lf2.lock(), is(true));
// verify who holds the lock
assertThat(lf2.readBytes(), equalTo(lf2.getPayload()));
// repeating same step should be idempotent
assertThat(lf1.lock(), is(false));
assertThat(lf2.lock(), is(true));
// verify who holds the lock
assertThat(lf2.readBytes(), equalTo(lf2.getPayload()));
} finally {
// cleanup
lf1.release();
lf2.release();
}
}
@Override
public Integer call() throws Exception {
for (int i = 0; i < attempts; i++) {
barrier.await(); // start together
try {
if (lockFile.lock()) {
locked++;
// verify that content of the file equals to our payload, as we own the lock
assertThat(lockFile.readBytes(), equalTo(lockFile.getPayload()));
}
barrier
.await(); // wait for others to attempt, and the one won should hold the lock during
// that
} catch (Exception e) {
// If an exception gets thrown, hang on to it so that it can be reported by the test
// Unconventional, but it seems the cyclic barrier rules out normal approach of getting
// the exception from Future.get()
this.caughtException = e;
} finally {
lockFile.release(); // the one locked should release for next attempt
}
}
return locked;
}