1) As explained in commit 697b16414a (gossip: Make gossip message
handling async), in each gossip round we can make talking to the 1-3
peer nodes in parallel to reduce latency of gossip round.
2) Gossip syn message uses one way rpc message, but now the returned
future of the one way message is ready only when message is dequeued for
some reason (sent or dropped). If we wait for the one way syn messge to
return it might block the gossip round for a unbounded time. To fix, do
not wait for it in the gossip round. The downside is there will be no
back pressure to bound the syn messages, however since the messages are
once per second, I think it is fine.
Message-Id: <ea4655f121213702b3f58185378bb8899e422dd1.1456991561.git.asias@scylladb.com>
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