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https://issues.apache.org/jira/browse/CASSANDRA-9206?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14500571#comment-14500571
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Jason Brown commented on CASSANDRA-9206:
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Actually, if all we really care about doing is increasing the fanout from a
fixed 1 to 2 nodes per gossip round (to aid in convergence), we could just
select two peers at random, rather than always selecting one random peer plus
one seed (as per the change in this ticket). This way seeds do not get the
extra load, and we still achieve the increased gossip sessions via a larger
fanout.
> Remove seed gossip probability
> ------------------------------
>
> Key: CASSANDRA-9206
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9206
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Brandon Williams
> Assignee: Brandon Williams
> Fix For: 2.1.5
>
> Attachments: 9206.txt
>
>
> Currently, we use probability to determine whether a node will gossip with a
> seed:
> {noformat}
> double probability = seeds.size() / (double)
> (liveEndpoints.size() + unreachableEndpoints.size());
> double randDbl = random.nextDouble();
> if (randDbl <= probability)
> sendGossip(prod, seeds);
> {noformat}
> I propose that we remove this probability, and instead *always* gossip with a
> seed. This of course means increased traffic and processing on the seed(s),
> but even a 1000 node cluster with a single seed will only put ~1000 messages
> per second on the seed, which is virtually nothing. Should it become a
> problem, the solution is simple: add more seeds. Since seeds will also
> always gossip with each other, this effectively gives us a poor man's
> spanning tree, with the only cost being removing a few lines of code, and
> should greatly improve our gossip convergence time, especially in large
> clusters.
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