Apache Solr Reference Guide Covering Apache Solr 6.0

master/slave shard.
For high availability you can use a load balancer to set up a virtual IP for each shard's set of slaves. If you are
new to load balancing, HAProxy ( http://haproxy.1wt.eu/ ) is a good open source software load-balancer. If a slave
server goes down, a good load-balancer will detect the failure using some technique (generally a heartbeat
system), and forward all requests to the remaining live slaves that served with the failed slave. A single virtual IP
should then be set up so that requests can hit a single IP, and get load balanced to each of the virtual IPs for the
search slaves.
With this configuration you will have a fully load balanced, search-side fault-tolerant system (Solr does not yet
support fault-tolerant indexing). Incoming searches will be handed off to one of the functioning slaves, then the
slave will distribute the search request across a slave for each of the shards in your configuration. The slave will
issue a request to each of the virtual IPs for each shard, and the load balancer will choose one of the available
slaves. Finally, the results will be combined into a single results set and returned. If any of the slaves go down,
they will be taken out of rotation and the remaining slaves will be used. If a shard master goes down, searches
can still be served from the slaves until you have corrected the problem and put the master back into production.
Merging Indexes
If you need to combine indexes from two different projects or from multiple servers previously used in a
distributed configuration, you can use either the IndexMergeTool included in lucene-misc or the CoreAdminH
andler.
To merge indexes, they must meet these requirements:
The two indexes must be compatible: their schemas should include the same fields and they should
analyze fields the same way.
The indexes must not include duplicate data.
Optimally, the two indexes should be built using the same schema.
Using IndexMergeTool
To merge the indexes, do the following:
1.
2.
Make sure that both indexes you want to merge are closed.
Issue this command:
java -cp $SOLR/server/solr-webapp/webapp/WEB-INF/lib/lucene-core-VERSION.jar:$
SOLR/server/solr-webapp/webapp/WEB-INF/lib/lucene-misc-VERSION.jar
org/apache/lucene/misc/IndexMergeTool
/path/to/newindex
/path/to/old/index1
/path/to/old/index2
This will create a new index at /path/to/newindex that contains both index1 and index2.
3. Copy this new directory to the location of your application's solr index (move the old one aside first, of
course) and start Solr.
Using CoreAdmin
The MERGEINDEXES command of the CoreAdminHandler can be used to merge indexes into a new core – either
from one or more arbitrary indexDir directories or by merging from one or more existing srcCore core names.
See the CoreAdminHandler section for details.
Apache Solr Reference Guide 6.0
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