[jboss-jira] [JBoss JIRA] (JGRP-2462) TransferQueueBundler: drop messages if queue is full
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https://issues.redhat.com/browse/JGRP-2462?page=com.atlassian.jira.plugin...
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Bela Ban commented on JGRP-2462:
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{quote}
Wouldn't you also have to implement explicit congestion notification as well, at least
from the transport to xFC, for RED/Blue to work?
{quote}
This could quickly become too complex... The xFC protocol at the sender still subtracts
the credits for a message M even if M ends up getting dropped by RED, so when the sender
runs out of credits, it will block until new credits have been received. This is similar
to TCP in which dropped packets slow down the sender.
{quote}
Also, would you have a single RED/Blue instance or all the members, or would each member
get a separate instance, so that when a node is really slow, messages can still be sent
normally to other nodes? I was thinking of JGRP-2463 and the coordinator having more load
with RELAY2.
{quote}
For now, I'll experiment with a single {{RED}} instance for _all_ members.
TransferQueueBundler: drop messages if queue is full
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Key: JGRP-2462
URL: https://issues.redhat.com/browse/JGRP-2462
Project: JGroups
Issue Type: Feature Request
Reporter: Bela Ban
Assignee: Bela Ban
Priority: Major
Fix For: 4.2.2, 5.0.0.Alpha4
When a bundler (like {{TransferQueueBundler}}) has a full queue, the senders will block.
This can happen for example when the TCP {{send}} blocks due to a full send-window.
Retransmission requests and responses compound the problem when the TQB's queue is
full.
Therefore, in addition to blocking, we should add an option to _drop_ packets when the
queue is full. Investigate whether we could use some priority based scheme, which drops
non-important messages first.
Also investigate whether senders can selectively be unblocked when the queue is full, to
either drop or add their messages. This could be done for example by removing elements
from the queue, using the aformentioned filter.
Look at random early detection )\[1\]) for inspiration.
\[1\] https://en.wikipedia.org/wiki/Random_early_detection
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