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From Otis Gospodnetic <otis.gospodne...@gmail.com>
Subject Re: SolrCloud Leaders
Date Mon, 22 Apr 2013 14:34:58 GMT
If the current leader dies, somebody's got to take over.

Otis
--
Solr & ElasticSearch Support
http://sematext.com/





On Mon, Apr 22, 2013 at 9:41 AM, Furkan KAMACI <furkankamaci@gmail.com> wrote:
> Hi Jack;
>
> You said: "An hour from now some other replica may be the leader"
>
> What is the criteria to change a leader of a shard?
>
> 2013/4/15 Jack Krupansky <jack@basetechnology.com>
>
>> All nodes are replicas in SolrCloud since there are no masters. It's a
>> fully distributed model. A leader is also a replica. A leader is simply a
>> replica which was elected to be a leader, for now. An hour from now some
>> other replica may be the leader.
>>
>> It is indeed misleading and inaccurate to suggest that "leader" and
>> "replicas" are disjoint.
>>
>> Once again, I think you are confusing SolrCloud with the older Solr
>> master/slave/replication.
>>
>> Every node in SolrCloud can do indexing. That's the same as saying that
>> every replica in SolrCloud can do indexing.
>>
>> Although we do need to be clear that a given replica will only index
>> documents for the shard(s) to which it belongs.
>>
>>
>> -- Jack Krupansky
>>
>> -----Original Message----- From: Furkan KAMACI
>> Sent: Monday, April 15, 2013 9:38 AM
>> To: solr-user@lucene.apache.org
>> Subject: Re: SolrCloud Leaders
>>
>> Here writes something:
>>
>> https://support.lucidworks.com/entries/22180608-Solr-HA-DR-overview-3-x-and-4-0-SolrCloud-and
>>
>> says:
>>
>> Both leaders and replicas index items and perform searches.
>>
>> How replicas index items?
>>
>>
>> 2013/4/15 Furkan KAMACI <furkankamaci@gmail.com>
>>
>>  Does leaders may response search requests (I mean do they store indexes)
>>> at when I run SolrCloud at first and after a time later?
>>>
>>>
>>> 2013/4/15 Jack Krupansky <jack@basetechnology.com>
>>>
>>>  When the cluster is fully operational, yes. But if part of the cluster is
>>>> down or split and unable to communicate, or leader election is in
>>>> progress,
>>>> the actual count of leaders will not be indicative of the number of
>>>> shards.
>>>>
>>>> Leaders and shards are apples and oranges. If you take down a cluster, by
>>>> definition it would have no leaders (because leaders are running code),
>>>> but
>>>> shards are the files in the index on disk that continue to exist even if
>>>> the code is not running. So, in the extreme, the number of leaders can be
>>>> zero while the number of shards is non-zero on disk.
>>>>
>>>> -- Jack Krupansky
>>>>
>>>> -----Original Message----- From: Furkan KAMACI
>>>> Sent: Monday, April 15, 2013 8:21 AM
>>>> To: solr-user@lucene.apache.org
>>>> Subject: SolrCloud Leaders
>>>>
>>>>
>>>> Does number of leaders at a SolrCloud is equal to number of shards?
>>>>
>>>>
>>>
>>>
>>

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