EMPessimistic

Pessimistic child processes for EventMachine.

EventMachine provides both EM.popen and EM::DeferrableChildProcess, but none of them are particularly useful in the case of your process exiting with an error.

EMPessimistic provides popen3 and a DeferrableChildProcess that caters for failing child processes.

API Docs

EMPessimistic.popen3(cmd, handler=nil, *args)

Works like EM::popen. Additionally, it sends data from the process' stderr to the handler's receive_stderr method.

require "em_pessimistic"
require "eventmachine"

class LsHandler < EventMachine::Connection
  def initialize(*args)
    puts "Initializing command"
  end

  def receive_data(data)
    puts "Received stdout: #{data}"
  end

  def receive_stderr(data)
    puts "Received stderr: #{data}"
  end

  def unbind
    puts "All done"
    EM.stop
  end
end

EM.run do
  EMPessimistic.popen3("ls -l", LsHandler)
  EMPessimistic.popen3("ls -l /oh/noes", LsHandler)
end

EMPessimistic.::DeferrableChildProcess

Works mostly like EM::DeferrableChildProcess.

If the process spawned by EMPessimistic::DeferrableChildProcess.open exits cleanly, the returned deferrable will invoke the callback with three arguments - data, which is a string representing the process' stdout, error, which is a string representing the process' stderr and status, which is a Process::Status object.

If the process spawned by EMPessimistic::DeferrableChildProcess.open exits with an error, the returned deferrable will invoke the errback with three arguments - error, which is a string representing the process' stderrdata, which is a string representing the process' stderr and status, which is a Process::Status object.

# I suppose that EM has already been run.

child = EMPessimistic::DeferrableChildProcess.open(command)

child.callback do |data, err, status|
  # Your code here...
end

child.errback do |data, err, status|
  # Your code here...
end

Installing

em_pessimistic ships as a gem:

$ gem install em_pessimistic

Or in your Gemfile:

gem "em_pessimistic", "~> 0.1"

Contributing

Contributions are welcome. To get started:

$ git clone git://gitorious.org/gitorious/em_pessimistic.git
$ cd em_pessimistic
$ bundle install
$ rake

When you have fixed a bug/added a feature/done your thing, create a clone on Gitorious or a fork on GitHub and send a merge request/pull request, whichever you prefer.

Please add tests when adding/altering code, and always make sure all the tests pass before submitting your contribution.

License

The MIT License (MIT)

Copyright (C) 2012 Gitorious AS and 2013 Andrey Chergik

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.