Prochestra

Prochestra is a small Python module for calling a set of processes with inter-dependencies in a series. It is meant to be used for assembling a set of process calls into one single call, e.g. in a cronjob.

A process call can have a number of dependencies. In a way, that it will not be executed, if one of its dependencies failed, or exited with return code other than 0, respectively. The return code of Prochestra is 0, if every subprocess call returned 0; otherwise it is 1.

The output of all processes is written to the stdout, one single logfile, or dismissed.

The process calls and its dependencies are defined in a JSON or YAML file.

Installation

Prochestra is published on PyPI:

pip install prochestra

Usage

A definition for three process calls with one dependency relationship could look like this:

jobs:
- id: j1
  cmd: "batchjob1"
  args: ["-c" "/usr/local/etc/someconfig"]
- id: j2
  cmd: "batchjob2"
- id: j3
  cmd: "batchjob3"
  dependencies:
  - j1

The processes are called in the given order. The jobs j1 and j2 are executed no matter what. But, job j3 is executed only, if the job j1 returned with exit code 0.

To run the job list, saved as jobs.yaml, run:

prochestra jobs.yaml

To find out all possible command line arguments for Prochestra, print the help text like this:

prochestra --help

Alternative Usage

If you download the project directly instead of using PIP for installation, you can run the scripts bin/prochestra (Bash) or bin\prochestra.cmd (Windows CMD) directly, or put bin on your PATH.

Another alternative is to run Prochestra as a module:

python -m prochestra myjobs.json

And finally you can use the classes JobList and Prochestra from the prochestra module in your own Python code if you want to dynamically generate job lists:

from prochestra import Prochestra, JobList

job_list = {'jobs': [
    {'id': 'j1', 'cmd': 'python', 'args': ['-c', 'print("Hello World 1"); exit(1)']},
    {'id': 'j2', 'cmd': 'python', 'args': ['-c', 'print("Hello World 2")'], 'dependencies': ['j1']},
    {'id': 'j3', 'cmd': 'python', 'args': ['-c', 'print("Hello World 3")']},
  ]}
runner = Prochestra()
result = runner.run(JobList(job_list))
if not result:
    print('At least one process failed.')

License

This project is released under the MIT license.

Copyright © 2017 by Tobias Kiertscher <dev@mastersign.de>.