public synchronized void unlock() {
        LOGGER.trace("Releasing lock on {}", file.getAbsolutePath());
        if (flock != null) {
            try {
                flock.release();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }
Unlock the lock if it is held
server-common/src/main/java/org/apache/kafka/server/util/FileLock.java