Neo4j doesn't autostart after deploying to heroku - heroku

Question

I'm trying to deploy a jruby rails app using the neo4j gem to Heroku. Running locally works fine but when I hit #new (//new) at Heroku's end, I get:
NoMethodError (undefined method `reference_node' for nil:NilClass):
After [some research][1], it seemed like my Neo4j server wasn't even running.
So I had to do
heroku run rails console
then
Neo4j.start
..in order to get my app working. But why doesn't Neo4j know to just wake up and start?
This is my Gemfile.lock:
GEM
remote: https://rubygems.org/
specs:
actionmailer (3.2.13)
actionpack (= 3.2.13)
mail (~> 2.5.3)
actionpack (3.2.13)
activemodel (= 3.2.13)
activesupport (= 3.2.13)
builder (~> 3.0.0)
erubis (~> 2.7.0)
journey (~> 1.0.4)
rack (~> 1.4.5)
rack-cache (~> 1.2)
rack-test (~> 0.6.1)
sprockets (~> 2.2.1)
activemodel (3.2.13)
activesupport (= 3.2.13)
builder (~> 3.0.0)
activerecord (3.2.13)
activemodel (= 3.2.13)
activesupport (= 3.2.13)
arel (~> 3.0.2)
tzinfo (~> 0.3.29)
activeresource (3.2.13)
activemodel (= 3.2.13)
activesupport (= 3.2.13)
activesupport (3.2.13)
i18n (= 0.6.1)
multi_json (~> 1.0)
arel (3.0.2)
builder (3.0.4)
coffee-rails (3.2.2)
coffee-script (>= 2.2.0)
railties (~> 3.2.0)
coffee-script (2.2.0)
coffee-script-source
execjs
coffee-script-source (1.6.2)
diff-lcs (1.2.4)
erubis (2.7.0)
execjs (1.4.0)
multi_json (~> 1.0)
hike (1.2.2)
i18n (0.6.1)
journey (1.0.4)
jquery-rails (2.2.1)
railties (>= 3.0, < 5.0)
thor (>= 0.14, < 2.0)
json (1.7.7-java)
mail (2.5.3)
i18n (>= 0.4.0)
mime-types (~> 1.16)
treetop (~> 1.4.8)
mime-types (1.23)
multi_json (1.7.2)
neo4j (2.2.3-java)
activemodel (>= 3.0.0, < 3.3)
neo4j-wrapper (= 2.2.3)
orm_adapter (>= 0.0.3)
railties (>= 3.0.0, < 3.3)
neo4j-community (1.8.1-java)
neo4j-core (2.2.3-java)
neo4j-community (>= 1.8.1, < 1.9)
neo4j-cypher (~> 1.0.0)
neo4j-cypher (1.0.0)
neo4j-wrapper (2.2.3-java)
neo4j-core (= 2.2.3)
orm_adapter (0.4.0)
polyglot (0.3.3)
puma (1.6.3-java)
rack (~> 1.2)
rack (1.4.5)
rack-cache (1.2)
rack (>= 0.4)
rack-ssl (1.3.3)
rack
rack-test (0.6.2)
rack (>= 1.0)
rails (3.2.13)
actionmailer (= 3.2.13)
actionpack (= 3.2.13)
activerecord (= 3.2.13)
activeresource (= 3.2.13)
activesupport (= 3.2.13)
bundler (~> 1.0)
railties (= 3.2.13)
railties (3.2.13)
actionpack (= 3.2.13)
activesupport (= 3.2.13)
rack-ssl (~> 1.3.2)
rake (>= 0.8.7)
rdoc (~> 3.4)
thor (>= 0.14.6, < 2.0)
rake (10.0.4)
rdoc (3.12.2)
json (~> 1.4)
rspec-core (2.13.1)
rspec-expectations (2.13.0)
diff-lcs (>= 1.1.3, < 2.0)
rspec-mocks (2.13.1)
rspec-rails (2.13.0)
actionpack (>= 3.0)
activesupport (>= 3.0)
railties (>= 3.0)
rspec-core (~> 2.13.0)
rspec-expectations (~> 2.13.0)
rspec-mocks (~> 2.13.0)
sass (3.2.8)
sass-rails (3.2.6)
railties (~> 3.2.0)
sass (>= 3.1.10)
tilt (~> 1.3)
sprockets (2.2.2)
hike (~> 1.2)
multi_json (~> 1.0)
rack (~> 1.0)
tilt (~> 1.1, != 1.3.0)
therubyrhino (2.0.2)
therubyrhino_jar (>= 1.7.3)
therubyrhino_jar (1.7.4)
thor (0.18.1)
tilt (1.3.7)
treetop (1.4.12)
polyglot
polyglot (>= 0.3.1)
tzinfo (0.3.37)
uglifier (2.0.1)
execjs (>= 0.3.0)
multi_json (~> 1.0, >= 1.0.2)
PLATFORMS
java
DEPENDENCIES
coffee-rails (~> 3.2.1)
jquery-rails
neo4j (>= 2.2.3)
puma
rails (= 3.2.13)
rspec-rails
sass-rails (~> 3.2.3)
therubyrhino
uglifier (>= 1.0.3)

Answer 1

This is most likely because Neo4j start-up is not (yet) thread-safe. Neo4j will actually start up the first time you hit your app. However, depending on the type of request(s), you could encounter the error described above from that point forward. Specifically, multiple requests to the app while Neo4j is starting up will result in errors until the app is restarted.
I submitted a fix for this (see here, here, and here) and it has been merged. However, it has not yet been included in an official gem release yet.
If you want to work around this issue for now, you have two options:
-Point to the neo4-core master branch
-Auto-start Neo4j on startup using the following monkey patch. This skirts around the thread-safety issue, because Rails won't accept any requests until Neo4j finishes starting up.
#config/initializers/neo4j.rb
require 'neo4j'
module Neo4j
class Railtie < ::Rails::Railtie
initializer "neo4j.db.start", :after => "neo4j.start" do |app|
Neo4j.start if app.config.neo4j.auto_start
end
end
end
#config/application.rb
config.neo4j.auto_start = true
Note that even with these fixes in place, I've still had trouble with the puma web server throwing strange exceptions. I would recommend torquebox-lite for production use - it's never fallen over for me.
UPDATE: Neo4j.rb v2.2.4 (released on May 19, 2013) includes this fix, so this patch will no longer be necessary after you upgrade.