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From Jonathan Rochkind <>
Subject Re: communication protocol between master and slave
Date Wed, 25 May 2011 18:21:34 GMT
I'm pretty sure it's over HTTP, although I don't know the details of the 

The slave will download any index files that have changed on master. A 
Solr index is split up amongst a number of seperate files on disk.  
There's no way for slave to get a delta beyond getting a complete index 
file if and only if it's changed --- index files that haven't changed 
won't be downloaded, index files that are new will be downloaded. (I 
think 'new' is basically the same as 'changed', I am not sure if index 
files are ever actually changed, rather than new ones being created and 
old ones (after a merge/optimize operation) being deleted).

One side effect of this is if an 'optimize' is run on master, then 
typically all index files will have to be downloaded. (Likewise if an 
optimize is run on slave, next replication all index files will be 
downloaded. There's generally no good reason to run an optimize on 
slave, or otherwise do anything to change the index at all on slave).

On 5/25/2011 1:11 PM, antoniosi wrote:
> Hi,
> I am just curious what is the communication protocol that a slave node get
> the index update from the master node in a replication settings? Is it
> through TCP? I assume it only gets the delta?
> Thanks very much in advance.
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