[jboss-jira] [JBoss JIRA] (JGRP-1570) STABLE: desired_avg_gossip leads to long intervals between reception of STABILITY messages in large clusters

[Bela Ban (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-1570?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12754793#comment-12754793 ] 

Bela Ban commented on JGRP-1570:
--------------------------------

The previous 2 comments apply to STABLE2 (JGRP-1595). This current JIRA issue is only about changing the defaults (desired_avg_gossip and max_bytes), by not scaling them with the cluster size.
This is a simple change, but we need to investigate how this impacts:
* STABLE / STABILITY messages required for a stable round
* Performance
                
> STABLE: desired_avg_gossip leads to long intervals between reception of STABILITY messages in large clusters
> ------------------------------------------------------------------------------------------------------------
>
>                 Key: JGRP-1570
>                 URL: https://issues.jboss.org/browse/JGRP-1570
>             Project: JGroups
>          Issue Type: Feature Request
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 3.3
>
>
> The time computed for the sending of STABLE is desired_avg_gossip * cluster-size *2. While this is OK for small clusters, it may be too big for large clusters.
> On the other hand, if every member simply multicasts a STABLE message every (say) 30 seconds on average, then the number of messages sent grows with increasing cluster size.
> Investigate a way to set a lower and upper limit for the making and delivery of *STABILITY* messages, e.g. the goal is to receive 1 stability message every 60s.
> Besides increased traffic, however, this requires everyone to have a TCP connection to everybody else in the cluster in case of a TCP transport.
> A better solution might be to have only a dedicated member (the coord) periodically multicast a STABLE message. Everyone replies with a (unicast) STABLE message and when the coord has received STABLE replies from everyone, it multicasts a STABILITY message. This would only require a multicast from the coord to everyone, establishing TCP connections from the coord to everyone (usually already exists because of the VIEW-CHANGE multicast), but everyone would reuse the same TCP connection to send the reply.

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