protected void forwardToCoord(long seqno, Message msg) {
if (is_coord) {
forward(msg, seqno, false);
return;
}
if (!running || flushing) {
forward_table.put(seqno, msg);
return;
}
if (!ack_mode) {
forward_table.put(seqno, msg);
forward(msg, seqno, false);
return;
}
send_lock.lock();
try {
forward_table.put(seqno, msg);
while (running && !flushing) {
ack_promise.reset();
forward(msg, seqno, true);
if (!ack_mode || !running || flushing) break;
Long ack = ack_promise.getResult(500);
if ((Objects.equals(ack, seqno)) || !forward_table.containsKey(seqno)) break;
}
} finally {
send_lock.unlock();
}
}
/**
* Sends all messages currently in forward_table to the new coordinator (changing the dest field).
* This needs to be done, so the underlying reliable unicast protocol (e.g. UNICAST) adds these
* messages to its retransmission mechanism<br>
* Note that we need to resend the messages in order of their seqnos ! We also need to prevent
* other message from being inserted until we're done, that's why there's synchronization.<br>
* Access to the forward_table doesn't need to be synchronized as there won't be any insertions
* during flushing (all down-threads are blocked)
*/
protected void flushMessagesInForwardTable() {
if (is_coord) {
for (Map.Entry<Long, Message> entry : forward_table.entrySet()) {
Long key = entry.getKey();
Message msg = entry.getValue();
Buffer buf;
try {
buf = Util.streamableToBuffer(msg);
} catch (Exception e) {
log.error(Util.getMessage("FlushingBroadcastingFailed"), e);
continue;
}
SequencerHeader hdr = new SequencerHeader(SequencerHeader.WRAPPED_BCAST, key);
Message forward_msg = new Message(null, buf).putHeader(this.id, hdr);
if (log.isTraceEnabled())
log.trace(local_addr + ": flushing (broadcasting) " + local_addr + "::" + key);
down_prot.down(new Event(Event.MSG, forward_msg));
}
return;
}
// for forwarded messages, we need to receive the forwarded message from the coordinator, to
// prevent this case:
// - V1={A,B,C}
// - A crashes
// - C installs V2={B,C}
// - C forwards messages 3 and 4 to B (the new coord)
// - B drops 3 because its view is still V1
// - B installs V2
// - B receives message 4 and broadcasts it
// ==> C's message 4 is delivered *before* message 3 !
// ==> By resending 3 until it is received, then resending 4 until it is received, we make sure
// this won't happen
// (see https://issues.jboss.org/browse/JGRP-1449)
while (flushing && running && !forward_table.isEmpty()) {
Map.Entry<Long, Message> entry = forward_table.firstEntry();
final Long key = entry.getKey();
Message msg = entry.getValue();
Buffer buf;
try {
buf = Util.streamableToBuffer(msg);
} catch (Exception e) {
log.error(Util.getMessage("FlushingBroadcastingFailed"), e);
continue;
}
while (flushing && running && !forward_table.isEmpty()) {
SequencerHeader hdr = new SequencerHeader(SequencerHeader.FLUSH, key);
Message forward_msg =
new Message(coord, buf).putHeader(this.id, hdr).setFlag(Message.Flag.DONT_BUNDLE);
if (log.isTraceEnabled())
log.trace(
local_addr
+ ": flushing (forwarding) "
+ local_addr
+ "::"
+ key
+ " to coord "
+ coord);
ack_promise.reset();
down_prot.down(new Event(Event.MSG, forward_msg));
Long ack = ack_promise.getResult(500);
if ((Objects.equals(ack, key)) || !forward_table.containsKey(key)) break;
}
}
}