When you try and run rake solr:start or rake solr:stop it uses Kernel.fork to spawn of a child process. However in JRuby this is disabled by default due to concurrency issues. And this prevents your solr rake tasks from running under a JRuby environment…
The Problem
When you try and run rake solr:start or rake solr:stop it uses Kernel.fork to spawn of a child process.
However in JRuby this is disabled by default due to concurrency issues. There is an option to enabling fork (jruby -J-Djruby.fork.enabled=true)
within JRuby but it is experimental and as the warning says, “WARNING: fork is highly unlikely to be safe or stable on the JVM.” as it can cause all sorts of weird and wonderful side-effects.
The Solution
The solution therefore is to simply alter the solr:start and solr:stop tasks to use Kernel.exec instead.
To do this find the solr rake tasks usually in {RAILS_ROOT}/vendor/acts_as_solr/lib/tasks/solr.rake. In the start task all that is required is to comment out the start of the fork block. so you only have the exec method call,
This will not start the solr process in the background. To do so you just have to add “&” at the end of the exec command, which causes the jar file to run in background mode.
