Overview

Tiny Python context manager implementing a simple command protocol over pipes (e.g no deep binding/integration required) The data is serialized as json and arbitrary payload can be attached to the commands (and returned in the responses). Use it whenever you want to use python code to drive a project that is not python, typically to automate testing or maybe prepare some input, coordinate with remote systems, mock a quick REST front-end, etc. The manager will spawn the specified subprocess and read/write to its stdin/stdout. Any unexpected process exit will raise an exception and commands can be issued either in blocking mode or with a timeout.

The receiving process (e.g what's being "driven") must of course do its part and read its stdin. Any json snippet terminated by \n should be considered and a response potentially written back (still as json) to its stdout. The command layout is as follows:

{
    "tag": <unique integer sequence>
    "cmd": <arbitrary label>
    "ext": <optional free-form json object>
}

The "ext" sub-object represents some optional free-form payload, both from the request and response point of view. The response must include the same tag plus the "ext" sub-object (which may be then set to whatever payload you wish to return back). A few simple use-cases:

    try: 
      with driven('/usr/local/bin/my-stuff') as proxy:
        proxy.ask('do something')
        reply = proxy.ask('configure', ext={'foo': 'bar'})
        if proxy.ask('shutdown', timeout=5.0) is None:
          raise Exception('unable to terminate gracefully within 5 seconds')
    except BadExit:
      print 'abnormal process exit' 

You can simply install this package via pip/git:

$ pip install git+https://github.com/opaugam/spika 

Samples

A trivial Go snippet is provided to illustrate how the stuff works in conjunction with a tiny control script. Just build and try it out:

$ cd samples/go
$ go build snippet.go
$ python runme.py

Support

Contact olivier.paugam@autodesk.com for more information about this project.