An example of deploying Perl applications with Fabric and Carton, with slides from a panel talk at pdx-pm.

Deploying Perl with Fabric and Carton¶

Carton, similar to Python’s pip or Node’s npm, allows for module version locking for more predictable deployments. Using the bundle mode, a local cache can be used for deployments, or using the standard deployment mode the carton.lock file will be used to install modules.

Combined with Carton, Fabric can be used to deploy exact copies of module dependencies to multiple servers, even in parallel. Fabric could also be used to rsync the local module cache for bundle installs.

Fabric and Carton Glue¶

Here is a working example of a Carton deployment using Fabric. Using App::local::lib::helper as the shell in the fabfile, bootstrap cpanminus and Carton and then deploy the application with Carton.

'''Deployment'''

from fabric.api import *
from fabric.contrib.project import rsync_project
from contextlib import contextmanager

import os.path

env.www_host = 'prod@server'
env.build_path = '/srv/www/site'
env.env_path = '/srv/www/envs/bootstrap'

@task
@hosts(env.www_host)
def bootstrap():
    '''Bootstrap environment'''
    if not exists(env.build_path):
        run('mkdir -p {build_path}'.format(**env))
    if not exists(env.env_path):
        run('mkdir -p {env_path}/{{lib,bin}}'.format(**env))
    with cd(env.env_path):
        env.cpanm = '{env_path}/bin/cpanm'.format(**env)
        if not exists(env.cpanm):
            run('curl -Lko {cpanm} "http://cpanmin.us"'.format(**env))
            run('chmod +x {cpanm}'.format(**env))
        run('{cpanm} -L . App::cpanminus'.format(**env))
        run('{cpanm} -L . App::local::lib::helper'.format(**env))
        run('{cpanm} -nL . carton'.format(**env))

@task
@hosts(env.www_host)
def deploy():
    '''Deploy master'''
    rsync_project(
        env.build_path,
        './',
        exclude=[
            '*.pyc',
            '.git',
            'local/',
        ]
    )
    with localenv():
        with cd(env.build_path):
            run('carton install')

@contextmanager
def localenv():
    '''Context manager for local::lib'''
    with settings(shell='{env_path}/bin/localenv /bin/sh -c'.format(**env)):
        yield

def exists(path):
    '''Same as the contrib.files.exists, only with a different test'''
    with settings(hide('everything'), warn_only=True):
        return not run('test -e "%s"' % path).failed
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