Lost connection to MySQL server during query error with Rails3, octopus replication gem

Question

I just upgrade my web service from Rails 2.3.8 to Rails 3.0.3

It's almost working well.

I has one problem, Lost connection error is occurred when the service is deployed with capistrano. About 3 times occurred every deployment. The service use octopus gem from https://github.com/tchandy/octopus for database replication with 1 master database and 2 slave database.

Mysql::Error: Lost connection to MySQL server during query: SELECT regions.* FROM regions WH ...

The problem is not occurred when octopus is not used with single database. But replication is needed for traffic.

Please, give me any advise. Thank you.

Answer 1

I'm the creator of Octopus.

Can you add this to your shards.yml file?

verify_connection: true

Also, if that don't work, try to configure rails to automatic reconnect:

http://guides.rubyonrails.org/2_3_release_notes.html#reconnecting-mysql-connections

Obs: this will work only with mysql adapter, not mysql2.

Answer 2

If your using Phusion Passenger and PassengerSpawnMethod smart.

# config/initializers/phusion_passenger.rb
if defined?(PhusionPassenger)
  PhusionPassenger.on_event(:starting_worker_process) do |forked|
    if forked
      # the following is *required* for Rails + "PassengerSpawnMethod smart".
      if defined?(ActiveRecord::Base)
        # force reconnect to "master" connection.
        ActiveRecord::Base.connection_pool.disconnect!

        # force reconnect to our octopus "slave" pools. This may include the "master" pool above.
        if defined?(Octopus)
          ActiveRecord::Base.connection_proxy.instance_variable_get(:@shards).each { |name, pool| pool.disconnect! }
        end
      end
    end
  end
end

This with:

# database.yml and shards.yml
reconnect: true