[jboss-jira] [JBoss JIRA] (JGRP-1675) CreditRequest in FlowControl is not OOB
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https://issues.jboss.org/browse/JGRP-1675?page=com.atlassian.jira.plugin....
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Radim Vansa commented on JGRP-1675:
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Seems that increasing the credit amount to high value is a workaround for the issue. The
problem is that the load was really high in our test - like 15k messages per second - and
if something (e.g. GC) breaks in, many messages are buffered in socket. When we start
processing them again, we process some of them, sending the responses and decreasing the
FC credits really fast. Then, the OOB tp is temporarily depleted (before we get the
replenish) and the other messages get discarded - the fact is that the request is much
smaller than the response, therefore the requestor can send many requests before reaching
the FC credit limit but the amount of responses that can be sent is much lower.
This results in the sudden loss of many messages allowing situation described in comments
above.
CreditRequest in FlowControl is not OOB
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Key: JGRP-1675
URL: https://issues.jboss.org/browse/JGRP-1675
Project: JGroups
Issue Type: Bug
Affects Versions: 3.4
Reporter: Radim Vansa
Assignee: Bela Ban
Fix For: 3.4
I have recently observed a repeated situation where many (or all) threads have been stuck
waiting for credits in FlowControl protocol.
The credit request was not handled on the other node as this is non-oob message and some
(actually many of them - cause unknown) messages before the request have been lost -
therefore the request was waiting for them to be re-sent.
However, these have not been re-sent properly as the retransmission request was not
received - all OOB threads were stuck in the FlowControl protocol as these handled some
other request and tried to send a response - but the response could not be sent until
FlowControl gets the credits.
The probability of such situation could be lowered by tagging the credit request to be
OOB - then it would be handled immediately. If the credit replenish message would then be
processed in regular OOB pool, this could get already depleted by many requests, but
setting up the internal thread pool would solve the problem.
Other consideration would be to allow releasing thread from FlowControl (let it send the
message even without credits) if it waits there for too long.
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