· neo4j

neo4j.rb HA: NameError: cannot load Java class org.neo4j.graphdb.factory.HighlyAvailableGraphDatabaseFactory

neo4.rb is a JRuby gem that allows you to create an embedded neo4j database and last week I was working out how to setup a neo4j 1.8.2 HA cluster using the gem.

There is an example showing how to create a HA cluster using neo4j.rb so I thought I could adapt that to do what I wanted.

I had the following Gemfile:

source 'http://rubygems.org'

gem 'neo4j', '2.2.4'

gem 'neo4j-community', '1.8.2'
gem 'neo4j-advanced', '1.8.2' 
gem 'neo4j-enterprise', '1.8.2'

And the following code copied from the example to start up the cluster:

require "rubygems"
require "bundler"
require 'fileutils'
require 'neo4j'

def start(machine_id)
  # override this default config with this machine configuration
  Neo4j.config['enable_ha'] = true
  Neo4j.config['ha.server_id'] = machine_id
  Neo4j.config['ha.server'] = "localhost:600#{machine_id}"
  Neo4j.config['ha.pull_interval'] = '500ms'
  Neo4j.config['ha.discovery.enabled'] = false
  other_machines = [1,2,3].map{|id| "localhost:500#{id}"}.join(',')
  puts "ha.initial_hosts: #{other_machines}"
  Neo4j.config['ha.initial_hosts'] = other_machines
  Neo4j.config['ha.cluster_server'] = "localhost:500#{machine_id}"

  Neo4j.config[:storage_path] = "db/neo#{machine_id}"

As per the example's instructions I started up an irb session and tried to start up an instance:

$ bundle exec install
$ bundle exec irb
irb(main):001:0> require 'myapp'
=> true
irb(main):002:0> start 1
ha.initial_hosts: localhost:5001,localhost:5002,localhost:5003
I, [2013-06-09T17:23:09.110000 #33848]  INFO -- : starting Neo4j in HA mode, machine id: 1 at localhost:6001 db /Users/markhneedham/projects/neo4j-rb-ha/db/neo1
NameError: cannot load Java class org.neo4j.graphdb.factory.HighlyAvailableGraphDatabaseFactory
	from org/jruby/javasupport/JavaClass.java:1225:in `for_name'
	from org/jruby/javasupport/JavaUtilities.java:34:in `get_proxy_class'
	from file:/Users/markhneedham/.rbenv/versions/jruby-1.7.1/lib/jruby.jar!/jruby/java/java_package_module_template.rb:4:in `const_missing'
	from /Users/markhneedham/.rbenv/versions/jruby-1.7.1/lib/ruby/gems/shared/gems/neo4j-core-2.2.4-java/lib/neo4j-core/database.rb:188:in `start_ha_graph_db'
	from /Users/markhneedham/.rbenv/versions/jruby-1.7.1/lib/ruby/gems/shared/gems/neo4j-core-2.2.4-java/lib/neo4j-core/database.rb:62:in `start'
	from org/jruby/ext/thread/Mutex.java:149:in `synchronize'
	from /Users/markhneedham/.rbenv/versions/jruby-1.7.1/lib/ruby/gems/shared/gems/neo4j-core-2.2.4-java/lib/neo4j-core/database.rb:53:in `start'
	from /Users/markhneedham/.rbenv/versions/jruby-1.7.1/lib/ruby/gems/shared/gems/neo4j-core-2.2.4-java/lib/neo4j/neo4j.rb:41:in `start'
	from /Users/markhneedham/projects/neo4j-rb-ha/myapp.rb:21:in `start'
	from (irb):2:in `evaluate'
	from org/jruby/RubyKernel.java:1066:in `eval'
	from org/jruby/RubyKernel.java:1392:in `loop'
	from org/jruby/RubyKernel.java:1174:in `catch'
	from org/jruby/RubyKernel.java:1174:in `catch'
	from /Users/markhneedham/.rbenv/versions/jruby-1.7.1/bin/irb:13:in `(root)'

A quick scan of the neo4j code indicated that the class HighlyAvailableGraphDatabaseFactory didn't actually exist in any of the neo4j 1.8.2 jars and Max then pointed out the neo4j.rb change log which indicated that the clustering example was based around a neo4j 1.9 cluster.

If we want to create a neo4j 1.8 cluster then we need to tweak the settings a bit.

The instructions are available from an earlier revision of the neo4j.rb repository but I've cloned the repository and created a 1.8HA tag for future reference.

Essentially we'd need to revert back to the '2.2.1' version of the neo4j.rb gem and then run a script to startup some Zookeeper instances before following a similar process as described at the beginning of this post.

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