Getting error 'another command is already in progress' for async requests

[quezacoatl]

I frequently get 'another command is already in progress' when performing asynchrous requests simultaneously. Am I doing something wrong?

I do something like this:

EM.run do
    df1 = pg.query_defer('select * from foo')
    df2 = pg.query_defer('select * from foo')
    df1.callback { |result|
      puts Array(result).inspect
    }
    df1.errback {|ex|
      raise ex
    }
    df2.callback { |result|
      puts Array(result).inspect
    }
    df2.errback {|ex|
      raise ex
    }
  end

/home/rubyuser/.rvm/gems/ruby-2.1.1/gems/eventmachine-1.0.3/lib/em/deferrable.rb:158:in `call'
/home/rubyuser/.rvm/gems/ruby-2.1.1/gems/eventmachine-1.0.3/lib/em/deferrable.rb:158:in `set_deferred_status'
/home/rubyuser/.rvm/gems/ruby-2.1.1/gems/eventmachine-1.0.3/lib/em/deferrable.rb:198:in `fail'
/home/rubyuser/.rvm/gems/ruby-2.1.1/gems/em-pg-client-0.3.2/lib/pg/em.rb:491:in `async_autoreconnect!'
/home/rubyuser/.rvm/gems/ruby-2.1.1/gems/em-pg-client-0.3.2/lib/pg/em.rb:568:in `block in exec_prepared_defer'

[royaltm]

You can't run concurrent parallel operations on the single PG::EM::Client connection instance. Neither you couldn't do it on a single PG::Connection.

What you need is a connection pool, which fortunately is included in this gem:

require 'pg/em/connection_pool'

pg = PG::EM::ConnectionPool.new(size: 10, dbname: 'foo')

where size: is a maximum number of allowed connections per pool, and the other options are passed directly to connection instances.

Then your example should work.

See "Connection Pool" chapter in README.md for some more examples.

[quezacoatl]

Ok, I see. Thank you very much!