[jboss-jira] [JBoss JIRA] Commented: (JGRP-774) STATE_TRANSFER: state transfer broken for large states

[Bela Ban (JIRA)]

    [ http://jira.jboss.com/jira/browse/JGRP-774?page=comments#action_12415582 ] 
            
Bela Ban commented on JGRP-774:
-------------------------------

Okay, the cause is this (A is the state provider, B the requester):
- A gets the unicast GET-STATE request
- This acquires a lock on the AckReceiverWindow for B
- The GET-STATE request is passed up
- The app provides the state and sends it back to B *in the same thread*
- Since the state is large, FRAG2 breaks it into smaller fragments messages)
- One of those messages gets blocked in FC.down() (above UNICAST), as we're out of credits
- B sends new credits to A, but A will *not* receive them as those credits (as *OOB* message) have to pass through UNICAST first
- However, UNICAST won't let the CREDIT message pass as the original GET-STATE request stilll holds the lock for B's AckReceiverWindow !

SOLUTION:
- OOB requests should *never* have to acquire the lock on an AckreceiverWindow; we simply add the request to the AckReceiverWindow, pass up the message, and then return
- This way, OOB messages will never block on other (unrelated) messages in UNICAST

TODO: apply the same code changes to NAKACK (see sub-issue)

> STATE_TRANSFER: state transfer broken for large states
> ------------------------------------------------------
>
>                 Key: JGRP-774
>                 URL: http://jira.jboss.com/jira/browse/JGRP-774
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bela Ban
>         Assigned To: Bela Ban
>            Priority: Critical
>             Fix For: 2.7, 2.6.3
>
>
> To reproduce:
> Shell #1:
> jt LargeState -provider -size 10000000 -props udp.xml
> Shell #2:
> jt LargeState -props udp.xml
> This fails with a state around 10MB, smaller states pass.
> Note that this only fails for STATE_TRANSFER, if we switch to STREAMING_STATE_TRANSFER, it passes !

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