Multi-process access in Heroku environment causes PubNub initialization to occasionally fail

[rafalyesware]

As noted in assaf/uuid#28 and assaf/uuid#6, the UUID gem has multi-process access issues in certain environments (in our case, running push workers in Heroku via Resque or Resque-Pools).

About 2,000 times during a 24-hour period, we see the following crash of the push worker:

Exception: NoMethodError
Error: undefined method `unpack' for nil:NilClass
/app/vendor/bundle/ruby/2.0.0/gems/uuid-2.3.7/lib/uuid.rb:377:in `read_state'
/app/vendor/bundle/ruby/2.0.0/gems/uuid-2.3.7/lib/uuid.rb:333:in `block in next_sequence'
/app/vendor/bundle/ruby/2.0.0/gems/uuid-2.3.7/lib/uuid.rb:367:in `block in open_lock'
/app/vendor/bundle/ruby/2.0.0/gems/uuid-2.3.7/lib/uuid.rb:364:in `open'
/app/vendor/bundle/ruby/2.0.0/gems/uuid-2.3.7/lib/uuid.rb:364:in `open_lock'
/app/vendor/bundle/ruby/2.0.0/gems/uuid-2.3.7/lib/uuid.rb:332:in `next_sequence'
/app/vendor/bundle/ruby/2.0.0/gems/uuid-2.3.7/lib/uuid.rb:263:in `initialize'
/app/vendor/bundle/ruby/2.0.0/bundler/gems/ruby-d159a072b272/lib/pubnub/client.rb:60:in `new'
/app/vendor/bundle/ruby/2.0.0/bundler/gems/ruby-d159a072b272/lib/pubnub/client.rb:60:in `initialize'
/app/vendor/bundle/ruby/2.0.0/bundler/gems/ruby-d159a072b272/lib/pubnub.rb:57:in `new'
/app/vendor/bundle/ruby/2.0.0/bundler/gems/ruby-d159a072b272/lib/pubnub.rb:57:in `new'
/app/app/classes/send_push.rb:50:in `connection'
/app/app/classes/send_push.rb:24:in `call'
/app/app/classes/send_push.rb:15:in `call'
/app/app/workers/push_worker.rb:46:in `perform'
/app/app/workers/push_worker.rb:28:in `perform'

It would be great if the PubNub gem didn't depend on an inheretly-multi-process-unsafe gem for UUID by default (uuidtools seems like a nice alternative, SecureRandom.uuid is a possibility as well).

[blazeroot]

Thanks for notice @rafalyesware, i'm checking it and i will apply fix asap.

[rafalyesware]

Thanks @blazeroot. FWIW, all the Ruby UUID gems seem to have some failing or another... I don't know if you really need a UUID or just a large unique value, but if you can do without a proper UUID the Mongo ObjectID seems like a great choice (c.f. http://docs.mongodb.org/manual/reference/object-id/) for multi-host / multi-process environments.

[geremyCohen]

@blazeroot FWIW, we don't need EXACTLY per the UUID-spec, just a UUID-like pattern that has an equivalent duplicates collision domain within its own alogrithm, and UUID's.

[blazeroot]

Fixed and tested. @rafalyesware please use master branch of pubnub and let me know if that helps.
ps. SecureRandom doesn't exist in 1.8 and we want pubnub to be compatible with ruby1.8.

[rafalyesware]

You guys are all right! 👍 Will try to pull this in to our code ASAP, thanks!

[rafalyesware]

@blazeroot Pulled the latest gem off master and it is working as promised. Thanks for the quick turnaround!

[blazeroot]

@rafalyesware No problem! I'm happy to hear that!