Question

Is it possible to reload Solr configuration without setting up Multicore or restarting the servlet container?

I would like to tweak some <analyzer> chains with the analysis tab in the admin, and tweak the parameters to my <requestHandler>, but having to restart the servlet container after every small change to schema.xml or solrconfig.xml is a bit of a pain and time consuming.

Answer 1

As best as I can tell, online reloading requires a Multicore configuration, which it turns out isn’t too hard:

Put this solr.xml into the solr home directory

<solr persistent="false" sharedLib="lib">
  <cores adminPath="/admin/cores" defaultCoreName="core0">
    <core name="core0" instanceDir="." />
  </cores>
</solr>

Restart the servlet container.

Hit a URL like this to reload the configuration:

http://localhost:8983/solr/admin/cores?action=RELOAD&core=core0

To remove the rest of the friction, you can set it up to automatically reload the configuration by running the following script within the conf directory.

get_on_fsevent.rb "http://localhost:8983/solr/admin/cores?action=RELOAD&core=core0"

get_on_fsevent.rb:

#!/usr/bin/env ruby
require 'rubygems'
require 'rb-fsevent'
require 'net/http'
require 'uri'

uri = URI.parse(ARGV.first)

fsevent = FSEvent.new
fsevent.watch Dir.pwd do |directories|
  puts "Detected change. Requesting #{ARGV.first}"
  puts Net::HTTP.get_response(uri)
end
fsevent.run