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From Flavio Junqueira <...@yahoo-inc.com>
Subject Re: Managing multi-site clusters with Zookeeper
Date Mon, 15 Mar 2010 23:13:04 GMT
On top of Ben's description, you probably need to set initLimit to  
several minutes to transfer 700MB (worst case). The value of  
syncLimit, however, does not need to be that large.


On Mar 15, 2010, at 7:24 PM, Benjamin Reed wrote:

> 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 :)
> thanx
> ben
> 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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