int port = handler.reservePort();
        handler.start(15, { executed.set(true) })
        client.maybePingOwner(port, 15, "lock", 50000, null)
        poll { assert executed.get() }
    }

    def "reserving port is safely reentrant"() {
        when:
        int port = handler.reservePort()

        then:
        handler.reservePort() == port
    }

        return ImmutableList.copyOf(reservations)
    }

    @Override
    public int assignPort() {
        try {
            lock.lock()
            return reservePort()
        } finally {
            lock.unlock()
        }
    }

    @Override
    public void releasePort(int port) {
        if (port == null || port < MIN_PRIVATE_PORT || port > MAX_PRIVATE_PORT) {

    @Override
    public void start(long lockId, Consumer<FileLockReleasedSignal> whenContended) {}

    @Override
    public void stop(long lockId) {}

    @Override
    public int reservePort() {
        return -1;
    }

    @Override
    public boolean maybePingOwner(int port, long lockId, String displayName, long timeElapsed, FileLockReleasedSignal signal) {
        return false;
    }

@ServiceScope(Scope.Global.class)
public interface FileLockContentionHandler {
    void start(long lockId, Consumer<FileLockReleasedSignal> whenContended);

    void stop(long lockId);

    int reservePort();

    /**
     * Pings the lock owner with the give port to start the lock releasing
     * process in the owner. May not ping the owner if: