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From Jeff Widman <j...@jeffwidman.com>
Subject Why are ephemeral nodes written to disk?
Date Tue, 09 Jan 2018 20:38:31 GMT
Ephemeral nodes only exist for the life of the client session.

As far as I understand, by definition, a client session ends when the
entire zookeeper ensemble goes down.

So I would expect that ephemeral nodes are only written to memory, not
disk. The ephemeral nodes would be sync'd across machines as a client
session can span multiple connections if a single zk server fails, but once
the ensemble is down there is no need to recover the ephemeral nodes from
disk.

However, when I looked at a zookeeper ensemble that is 99% ephemeral nodes,
I see a bunch of disk I/O from the zookeeper processes. So it appears that
ephemeral nodes are still written to disk...

Why is this?

-- 

*Jeff Widman*
jeffwidman.com <http://www.jeffwidman.com/> | 740-WIDMAN-J (943-6265)
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