Neo4j::Rails Config

Configuration

You can set the location of the database in the config/application.rb file.
Example:

config.neo4j.storage_path = "#{config.root}/db/neo4j-#{Rails.env}"
config.neo4j.timestamps = false  # disable automatic timestamps on updated_at and created_at properties

Rails Console

The rails console will start up in read-only mode if you already have a running rails application since Neo4j does not allow write access to the database from several processes.

As a workaround you can use Neo4j HA which will replicate databases between processes.
To enable write access from a rails console using Neo4j HA:

1. add development dependencies to your Gemfile: neo4j-advanced and neo4j-enterprise (check license)
2. in your application/config.rb, add
   

   require 'neo4j/rails/ha_console/railtie' if Rails.env.development?

3. in config/application.rb : `config.neo4j.storage_path = … unless Rails.env.development?`

This will start a zookeeper process, configure the database location and configure Neo4j to use HA.
To shutdown the zookeeper:

Neo4j::Rails::HaConsole.shutdown_zookeeper

This is currently not released yet (use latest source from Github).

Deployment

• Installing JRuby – see RVM
• Tomcat/Trinidad
• “TorqueBox”
• Glassfish App Server

Trinidad needs the Java jar files in the lib folder.
There is a script for doing this:

neo4j-jars -local

Just type neo4j-jars for help

If you forget to add those jar files to your rails project you may get the following error message:

No index provider 'lucene' found

Backup

See Configuration & Backup

Add the following line in your config/application.rb file:

config.neo4j.online_backup_enabled = true

Then add the correct jar files to the lib folder:

neo4j-jars -backup

To perform the backup

require 'neo4j'
Neo4j.load_online_backup
Neo4j::OnlineBackup('localhost').incremental('/var/backup')

HA Cluster

See the example – https://github.com/andreasronge/neo4j/tree/master/example/ha-cluster

Example of a config/application.rb file:

config.neo4j['ha.db']=true
config.neo4j['ha.server_id']=1
config.neo4j['ha.server'] = 'localhost:6001'
config.neo4j['ha.coordinators] = 'localhost:2181,localhost:2182,localhost:2183'

Then add the correct jar files to the lib folder (when using a servlet container):

cd YOUR_RAILS_ROOT

neo4j-jars enterprise

Add the neo4j-advanced and neo4j-enterprise gems to your Gemfile.

Notice, if you are trying to create a new HA database you need to set the
configuration option `keep_logical_logs=true` and then create a transaction on the master, or copy the complete database to the new HA instance (I think …). Make sure the nioneo_logical.log.vXX files are available on the server db.

FAQ

java.lang.IllegalArgumentException: No cache type ‘soft’

You probably for forgot to run neo4j-jars command to copy the jar files to the lib folder.
This is normally needed for trinidad and warbler deployments.

I get “No index provider ‘lucene’ found”

See deployment above.

org.neo4j.kernel.impl.core.ReadOnlyDbException

You get this exception if there is already an neo4j db instance running.
Only one write instance of the database is possible. If there is already a write instance running then a read only db will be created.
Did you run the rails console before you did the first request to rails ?

Does neo4j have an Identity Map ?

Yes and it is enabled by default (in >= 2.0.0). Read more about it here: the identity map
and Neo4j::IdentityMap

Why can’t I update nested models: node.nested << x; node.nested.save ?

Because you have not enabled identity map, see above.
Let say you have the following class:

class Person < Neo4j::Rails::Model
  has_one(:nested)
end

node = Person.create
node.nested = Person.create
node.save

Then you can’t update the node.nested

node.nested[:some_property] = 'some value'
node.nested.nested << other_node
node.nested.save

Instead you must use a temporary variable, like this:

tmp = node.nested
tmp[:some_property] = 'some value'
tmp.nested << other_node
tmp.save

The reason is that the node.nested creates a new instance of a
wrapped node.

However, the following will work:

n = Person.create
n.nested = Person.create
n.nested[:name] = 'foo'
n.save

n.nested[:name] # => 'foo'

You do not need a temporary variable in this case since the relationship is not
persisted yet.