[jboss-jira] [JBoss JIRA] (JGRP-1961) TCP_NIO2: message bundling can lead to corruption of msgs sent asynchronously

[Bela Ban (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-1961?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13105943#comment-13105943 ] 

Bela Ban edited comment on JGRP-1961 at 9/6/15 11:05 AM:
---------------------------------------------------------

Hmm, how about we push the copy logic into {{WriteBuffers}} which could be configured to enable/disable copying on an unsuccessful write: if a {{write(b1,b2,b3,b4)}} was unsuccessful and only wrote {{b1}}, {{b2}} and *parts of* {{b3}}, but not {{b4}}, then null {{b1}} and {{b2}} and *copy* {{b3}} and {{b4}}, leaving {{position}} and {{limit}} of {{b3}} and {{b4}} intact.
Hmm, what happens if the next write also fails ? How do we prevent an additional copy ?


was (Author: belaban):
Hmm, how about we push the copy logic into {{WriteBuffers}} which could be configured to enable/disable copying on an unsuccessful write: if a {{write(b1,b2,b3,b4)}} was unsuccessful and only wrote {{b1}}, {{b2}} and *parts of* {{b3}}, then null {{b1}} and {{b2}} and *copy* {{b3}} and {{b4}}, leaving {{position}} and {{limit}} of {{b3}} and{{b4}} intact.
Hmm, what happens if the next write also fails ? How do we prevent an additional copy ?

> TCP_NIO2: message bundling can lead to corruption of msgs sent asynchronously
> -----------------------------------------------------------------------------
>
>                 Key: JGRP-1961
>                 URL: https://issues.jboss.org/browse/JGRP-1961
>             Project: JGroups
>          Issue Type: Bug
>    Affects Versions: 3.6.5
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>            Priority: Critical
>             Fix For: 3.6.6
>
>
> When a message is sent with a message bundler (in {{TP}}), the output buffer in {{TP.BaseBundler}} is reused for all messages of a given bundle (say {{m1}} and {{m2}}).
> This works for {{TCP}} because a write _blocks_ and - when it returns - we're guaranteed that the buffer has been copied into an OS buffer (TCP's send window).
> However, this is different with {{TCP_NIO2}}: *an async write always returns immediately, irrespective of whether the data was written completely, partially, or not at all !*
> If a write only writes a part of its data, on returning from the write, the message bundler reuses the output buffer and can thus overwrite and corrupt buffers that are in transit, waiting to be written.
> A quick check where buffers were copied fixed the problem.
> TODO: see where we need to copy data when using a bundler. Possibly only copy if a write didn't write all of the data.



--
This message was sent by Atlassian JIRA
(v6.4.11#64026)