Barrier subscriptions overwrite each other

[krakowski]

Barriers seem to be implemented using dynamic message receivers, which block until a specific message arrives. Whenever someone creates two of them, the second overwrites the firsts subscription. In addition a semaphore is used, which results in blocking one of the available message handler threads.

dxram/src/main/java/de/hhu/bsinfo/dxram/lookup/overlay/OverlayPeer.java

Lines 813 to 844 in 70d6f34

	public BarrierStatus barrierSignOn(final int p_barrierId, final long p_customData, final boolean p_waitForRelease) {
	if (p_barrierId == BarrierID.INVALID_ID) {
	return null;
	}
	Semaphore waitForRelease = new Semaphore(0);
	MessageReceiver msg = null;
	final BarrierReleaseMessage[] releaseMessage = {null};
	if (p_waitForRelease) {
	msg = p_message -> {
	if (p_message != null) {
	if (p_message.getType() == DXRAMMessageTypes.LOOKUP_MESSAGES_TYPE) {
	switch (p_message.getSubtype()) {
	case LookupMessages.SUBTYPE_BARRIER_RELEASE_MESSAGE: {
	releaseMessage[0] = (BarrierReleaseMessage) p_message;
	if (releaseMessage[0].getBarrierId() == p_barrierId) {
	waitForRelease.release();
	}
	break;
	}
	default:
	break;
	}
	}
	}
	};
	// make sure to register the listener BEFORE sending the sign on to not miss the release message
	m_network.register(DXRAMMessageTypes.LOOKUP_MESSAGES_TYPE, LookupMessages.SUBTYPE_BARRIER_RELEASE_MESSAGE,
	msg);
	}