Hemp 0.1.9

Tools for Fabric

Environment aware configuration and tools for Fabric.

Installation

pip install hemp

What is Hemp

Hemp is wrapper around Fabric that gives Fabric some environmental awareness and allows for use of configuration

files to set common or per-environment variables to be used in Fabric scripts.

Hemp is considered stable and production ready.

It is used internally by MobileCashout and has been

used to perform thousands of production deployments and uncountable amount of automation

tasks across multitude of platforms without any issues so far.

Usage

Hemp executable wraps Fabric and performs some subtle alterations to how Fabric is loaded and executed, namely,

loading default tasks and configuration files before Fabric execution.

The command line interface is not any different than Fabric itself, so, running your tasks

as usual and replacing fab with hemp should work out of the box.

Differences from Fabric

Fabfile location

By default, Fabric will load fabfile.py from current working directory or any of the parent directories.

Hemp extends this functionality to include fabfile.py located in $HOME of the current user.

This allows you to define your custom, shared utilties and tasks in one file, and use them without specifying the file

location explicitly when using Hemp.

Hemp files

Hemp loads configuration from Hemp configuration files called hemp.yml. They are loaded, by default, from $HOME

of the current user and current working directory.

If hemp.yml if found both at home directory of the user and current working directory, both files are loaded and

their contents merged recursively with contents of the hemp.yml located in current working directory taking precedence.

Default stages

By default, specifying a stage requires stage config to be loaded before any other tasks are executed. It can be done

by invoking hemp with one of the predefined stage tasks or a custom one, passing the name as an argument to on task.

Consider these samples:

hemp development [task]

hemp on:development [task]

will ultimately result in development stage to be used.

Sample environment configuration

hemp:
  environments:
    staging:
      roles:
        web: ['web0.host.com']
        db: ['web0.host.com']
    production:
      roles:
        web: ['web1.host.com', 'web2.host.com', 'web3.host.com', 'web4.host.com']
        db: ['web1.host.com']
    development:
      roles:
        web: ['web5.host.lan']
        db: ['web5.host.lan']
# [...]

Loading the hosts and roledefs

When invoked with one of the stage tasks or on task, Hemp will load appropriate configs to Fabric’s env dictionary.

For example, loading staging stage will populate env with fallowing values:

env.hosts = ['web0.host.com']
env.roledefs['web'] = ['web0.host.com']
env.roledefs['db'] = ['web0.host.com']

Host and role definition merging

Instead of overwriting, Hemp will merge whatever values there are already located in env dictionary, both for hosts

and role definitions.

Additional env settings

All root keys of the hemp.yml file will be loaded into Fabric’s env dictionary. For example, having configuration like

hosts: ['a.com', 'b.com']
hemp: [
    # ...
]

will result in env.hosts to be populated with a.com and b.com

License

Licensed under terms and conditions of Apache 2.0 license.