Question

I created a library that would record events to MongoDB from my Rails application. I’m using version 1.4.0 of the mongo gem and Rails 3.0 w/Ruby 1.8.7. The relevant code is:

def new_event(collection, event)
  @conn = Mongo::Connection.new("localhost", 27017, :pool_size => 5, :pool_timeout => 5)
  @conn.db("event").collection(collection).insert(event)
  @conn.close
end

This has worked fine for recording new events as they happen on the site. However, I also need to backfill the db with old events. So I’m doing running a script that basically does this:

SomeModel.find_each do |model|
  Tracker.new.new_event("model_event", { ... info from model ... })
end

I’m trying to backfill something on the order of 50k events. As the script runs, I see this:

Tue Sep 27 23:45:20 [initandlisten] waiting for connections on port 27017
Tue Sep 27 23:46:20 [clientcursormon] mem (MB) res:12 virt:78 mapped:0
Tue Sep 27 23:48:49 [initandlisten] connection accepted from 127.0.0.1:51006 #1
Tue Sep 27 23:49:03 [conn1] remove event.application 103ms
Tue Sep 27 23:49:12 [conn1] remove event.listing 127ms
Tue Sep 27 23:49:20 [clientcursormon] mem (MB) res:37 virt:207 mapped:128
Tue Sep 27 23:51:44 [initandlisten] connection accepted from 127.0.0.1:48103 #2
Tue Sep 27 23:51:44 [conn2] end connection 127.0.0.1:48103
Tue Sep 27 23:51:44 [initandlisten] connection accepted from 127.0.0.1:48104 #3
Tue Sep 27 23:51:44 [conn3] end connection 127.0.0.1:48104
Tue Sep 27 23:51:44 [initandlisten] connection accepted from 127.0.0.1:48105 #4
Tue Sep 27 23:51:44 [conn4] end connection 127.0.0.1:48105
Tue Sep 27 23:51:44 [initandlisten] connection accepted from 127.0.0.1:48106 #5
Tue Sep 27 23:51:44 [conn5] end connection 127.0.0.1:48106

The ports (127.0.0.1:XXXXX) and (what I assume are) the Connection Pool #s keep incrementing, until eventually I get this exception from the ruby script:

Failed to connect to a master node at localhost:27017
/var/bundler/turtle/ruby/1.8/gems/mongo-1.4.0/lib/../lib/mongo/connection.rb:526:in `connect'
/var/bundler/turtle/ruby/1.8/gems/mongo-1.4.0/lib/../lib/mongo/connection.rb:688:in `setup'
/var/bundler/turtle/ruby/1.8/gems/mongo-1.4.0/lib/../lib/mongo/connection.rb:104:in `initialize'

Answer 1

Just found the solution. I needed to make the connection object a class variable so it was shared across all instances of the Tracker class.

@@conn = Mongo::Connection.new("localhost", 27017, :pool_size => 5, :pool_timeout => 5)
def self.new_event(collection, event)
  @@conn.db("event").collection(collection).insert(event)
end