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Zookeeper >> mail # user >> More sync questions


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Re: More sync questions
Hi Jordan, exists is a read operation, check processRequest in  
FinalRequestProcessor.

-Flavio

On Nov 23, 2011, at 7:53 PM, Jordan Zimmerman wrote:

> Flavio, what I saw in the code (bear in mind I've only casually  
> looked at
> the code) is that getData, getChildren, etc. use the local server's  
> view.
> exists() appears to follow the same path as create(), etc. in that  
> it goes
> through the leader.
>
> -JZ
>
> On 11/23/11 10:23 AM, "Flavio Junqueira" <[EMAIL PROTECTED]> wrote:
>
>> In the way I understood the question, Jordan seems to have observed
>> that sync() is not affecting exists (correct me if I'm wrong,  
>> please).
>> If that's the case, then I believe we have a bug.
>>
>> -Flavio
>>
>> On Nov 23, 2011, at 6:01 PM, Patrick Hunt wrote:
>>
>>> On Thu, Nov 10, 2011 at 10:29 PM, Jordan Zimmerman
>>> <[EMAIL PROTECTED]> wrote:
>>>> A while back I asked about sync() and got responses that said it's
>>>> only needed for reads (getData, getChildren). I was looking through
>>>> the source and it appears that this does _not_ apply to exsists().
>>>> Am I reading that correctly? i.e. will exists() always return an
>>>> accurate (in terms of the leader) view of a node's metadata?
>>>
>>> No, sync applies to any read. We call it "slow read" in some cases
>>> because it forces the follower to get up to date with the leader.
>>>
>>> Keep in mind that any read from any server is never "accurate" at
>>> least in the sense that you likely mean it. e.g. the state of
>>> leadership may change btw the time the server responds to your  
>>> exists
>>> call and the time it takes for TCP/OS to propagate the response to
>>> your client.
>>> http://en.wikipedia.org/wiki/Fallacies_of_Distributed_Computing
>>>
>>> Patrick
>>
>> flavio
>> junqueira
>>
>> research scientist
>>
>> [EMAIL PROTECTED]
>> direct +34 93-183-8828
>>
>> avinguda diagonal 177, 8th floor, barcelona, 08018, es
>> phone (408) 349 3300    fax (408) 349 3301
>>
>

flavio
junqueira

research scientist

[EMAIL PROTECTED]
direct +34 93-183-8828

avinguda diagonal 177, 8th floor, barcelona, 08018, es
phone (408) 349 3300    fax (408) 349 3301

NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB