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From "Jaakko Laine (JIRA)" <>
Subject [jira] Commented: (CASSANDRA-617) gossiper scalability
Date Wed, 09 Dec 2009 15:07:18 GMT


Jaakko Laine commented on CASSANDRA-617:

As for the fixes...

(1) I think the easiest way would be to give Gossiper a chance to send multiple Syn messages
per round. If it cannot send "enough" (enough being certain threshold percentage) digests
compared to how many endpoints there are in all, it could send multiple Syn messages to the
same host. Gossiper messages are independent of each other, so they can be handled separately.
The downside would be that there is potentially quite a number of endpoint states to handle
per one round. However, since current way is for all nodes to know about all other nodes,
this will put a cap to scalability at some point in any case. (No idea at what point, though).

(2a) Depends on (1). If we can send multiple messages per round, then this one goes away.
(2b) Multiple messages will also solve this. However, if we stick to one message per round,
we might consider guaranteeing certain chunk of packet for both purposes.

(3a) When handling Syn message with only one digest (the sending node), include random endpoint
state information in the reply as much as there is room. This way a new node does not need
to wait for syn message from the seed to start gathering information about other nodes.
(3b) Might not be a big issue, but in order to squeeze more endpoint states to gossip messages,
perhaps it would be good idea to reduce the number of "move" states from four separate states
to one. This would decrease the total amount of data in Gossiper "cloud" potentially by tens
of percents. Would speed up the process of new node gathering node info.

> gossiper scalability
> --------------------
>                 Key: CASSANDRA-617
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.5
>            Reporter: Jaakko Laine
>             Fix For: 0.5
>         Attachments: averages.png, spread_100.png, spread_50.png, spread_90.png
> Improve gossiper scalability.

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