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From Benjamin Reed <br...@yahoo-inc.com>
Subject Re: Managing multi-site clusters with Zookeeper
Date Mon, 15 Mar 2010 18:24:10 GMT
it is a bit confusing but initLimit is the timer that is used when a 
follower connects to a leader. there may be some state transfers 
involved to bring the follower up to speed so we need to be able to 
allow a little extra time for the initial connection.

after that we use syncLimit to figure out if a leader or follower is 
dead. a peer (leader or follower) is considered dead if syncLimit ticks 
goes by without hearing from the other machine. (this is after the 
initial connection has been made.)

please open a jira to made the text a bit more explicit. feel free to 
add suggestions :)


On 03/15/2010 04:17 AM, Michael Bauland wrote:
> Hi Patrick,
> I'm also setting up a Zookeeper ensemble across three different
> locations and I've got some questions regarding the parameters as
> specified on the page you mentioned:
>> That's controlled by the "tickTime"/synclimit/initlimit/etc.. see more
>> about this in the admin guide: http://bit.ly/c726DC
> - What's the difference between initLimit and syncLimit? For initLimit
> it says this is the time "to allow followers to connect and sync to a
> leader," and syncLimit is the time "to allow followers to sync with
> ZooKeeper". To me this sounds very similar, since "Zookeeper" in the
> second definition probably means the Zookeeper leader, doesn't it?
> - When I connect with a client to the Zookeeper ensemble I provide the
> three IP addresses of my three Zookeeper servers. Does the client then
> choose one of them arbitrarily or will it always try to connect to the
> first one first? I'm asking since I would like to have my clients first
> try to connect to the local Zookeeper server and only if that fails (for
> whatever reason, maybe it's down) it should try to connect to one of the
> servers on a different physical location.
>> You'll want to increase from the defaults since those are typically for
>> high performance interconnect (ie within colo). You are correct though,
>> much will depend on your env. and some tuning will be involved.
> Do you have any suggestions for the parameters? So far I left tickTime
> at 2 sec and increased initLimit and syncLimit to 30 (i.e., one minute).
> Our sites are connected with 1Gbit to the Internet, but of course we
> have no influence on what's in between. The data managed by zookeeper is
> quite large (snapshots are 700 MByte, but they may increase in the future).
> Thanks for your help,
> Michael

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