[jboss-jira] [JBoss JIRA] (JGRP-2281) MERGE3 blocks unnecessarily in discovery when non-multicast transport is used

[Bela Ban (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-2281?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13597497#comment-13597497 ] 

Bela Ban commented on JGRP-2281:
--------------------------------

New event {{FIND_MBRS_ASYNC}} was created with arg {{Consmer<PingData>}}. The arg is a callback that's invoked whenever a discovery response is received

> MERGE3 blocks unnecessarily in discovery when non-multicast transport is used
> -----------------------------------------------------------------------------
>
>                 Key: JGRP-2281
>                 URL: https://issues.jboss.org/browse/JGRP-2281
>             Project: JGroups
>          Issue Type: Enhancement
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 4.0.13
>
>
> When MERGE3 uses TCP, it cannot multicast its INFO message, and therefore uses the discovery protocol (e.g. MPING) to fetch the targets to send the INFO message to.
> Since we don't know how many responses to expect, we simply block for {{(min_interval + max_interval /2) ms}}. This is bad, as it delays the sending of INFO messages, which results in a partial merge as we're likely not to get responses from *all* members. This delays a full merge, e.g. when we have many singleton subclusters. A heavily split cluster will therefore likely require more merge rounds than necessary when using TCP, compared to (e.g.) UDP.
> h4. Solution:
> * The discovery process should be _reactive_ rather than blocking: instead of waiting for N seconds, we simply pass a function to the discovery protocol that gets invoked whenever a response has been received
> * When the function gets invoked, it sends an INFO to the respective member
> * This prevents 1 thread from blocking for N seconds
> See \[1\] for details.
> \[1\] https://github.com/belaban/JGroups/pull/389



--
This message was sent by Atlassian JIRA
(v7.5.0#75005)