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From Per Steffensen <st...@designware.dk>
Subject Re: Exposing Solr routing to SolrJ client
Date Mon, 12 Mar 2012 13:39:46 GMT
Mark Miller skrev:
> Hey Per,
>
> A couple things:
>
> 1. Distributed realtime get is coming - I know Yonik was looking at this recently but
got caught up in some other things.
>   
Fantistic! I believe, if the client becomes "routing aware", it is only 
necessary when you are sending more than one id (using "ids") in your 
realtime-get request, and even then the distribution (to several Solr 
servers and merging of results from those) could happen in the client 
(or not, if you dont think that is appropriate).
> 2. There is a Solrj client that is aware of the cluster state - its called CloudSolrServer.
You give it the zookeeper address rather than a node's address. Currently it doesn't send
directly to the leader, but this is planned
Nice! So you plan to solve the "two hop" problem (as ElasticSearch calls 
it) that I was mentioning! 
http://www.elasticsearch.org/guide/reference/java-api/client.html
>  - it's a little tricky due to lack of access to the Schema for hashing, but likely coming
soon - there is a JIRA issue for it. Clients in other languages should be able to do the same
thing.
>   
But can I do realtime-get from a SolrJ client already, then? You say 
that CloudSolrServer does not go directly to leader yet, and if I am 
correct when I claim that realtime-get (/get) requests are not routed on 
serverside to leader, then I will still not be able to do realtime-get 
using CloudSolrServer. Am I correct that I cant do it yet, even using 
CloudSolrServer?

BTW, congratulations and thanks, for the terrific work you guys are 
doing on Solr(Cloud)! Hope to get to contribute "versioning" (for 
optimistic locking) and a "unique key" feature that allows the operation 
to fail if the document already exists (instead of just automatically 
deleting what is already there).
> - Mark
>
> On Mar 12, 2012, at 5:26 AM, Per Steffensen wrote:
>
>   
>> Hi
>>
>> I believe Solr(Cloud) is doing some internal routing of update-requests to make sure
documents are stored in the correct core/shard decided by Solrs internal routing algoritm
(I believe it basically finds out who is the leader-shard for a given document, using shared
information in ZK, info about the collection and hash(document.id)). All nice and cool.
>>
>> I also believe realtime-gets are not forwarded internally in Solr through this routing
algorithm, and that it therefore is "impossible" to do realtime-gets from a client, because
you dont know which core/shard to contact directly, again because you dont know the routing
alogrithm. If Im wrong, it would be very helpfull with a few directions on how to do realtime-gets
from a client to a Solr servers system containing many shards and collection. If Im right,
I think it would be very nice if the the routing algorithm was somehow exposed to the client
(in code reachable from SolrJ) so that you can get to do realtime-gets from a SolrJ-based
client - if it should be done automatically for you of if the client using SolrJ explicitly
needs to call some code to get info about the core to contact, is not so important for now.
>>
>> Such a solution would also make it possible to get rid of another performance related
"problem", that most update-requests has to be transported among JVMs twice to reach their
destination. First from client to some "random" Solr server, and then from this Solr server
to the Solr server holding the core involved in the update. If routing information was available
for the client it could make sure to route its updates directly to the core (the one currently
playing the role as leader-shard for the shard to which the routing algorithm maps the document)
involved in the update.
>>
>> ElasticSearch has a solution to this problem by the usage of "Node Client" (instead
of just "Transport Client"), where a node client is basically a real node in the system that
just doesnt store document, but which have all the logic and shared information like e.g.
routing algorithm available - http://www.elasticsearch.org/guide/reference/java-api/client.html.
It certainly doesnt have to be like that with Solr clients, but it would be nice if somehow
routing logic where available to the SolrJ so that it can send its updates (and realtime-gets)
directly to the correct destination.
>>
>> Hope to get some comments on this issue.
>>
>> Regards, Per Steffensen
>>
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>>     
>
> - Mark Miller
> lucidimagination.com
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