The Rolling Pin

A tool for rolling changes out to servers.

To roll stuff out, select a group of hosts to affect:

• a master list of hosts is collected by the "host source" which is pluggable.
• aliased hostname glob expressions specify which hosts to pay attention to (-h)
• the list may be truncated by starting after (--startat) or stopping before (--stopbefore) specified hosts

And what commands you'd like to run:

• components to deploy get built on configurable build servers then deployed to individual hosts (-d)
• restart services (-r)
• arbitrary other commands may be specified as long as the remote end knows how to execute them (-c)

The rollout will then begin:

• rollouts are executed by the "transport" which is pluggable and defaults to ssh.
• hosts are "enqueued" one at a time with an optional delay between them (--sleeptime)
• multiple hosts can be worked on in parallel (--parallel)
• after a number of hosts have completed their work, the rollout can pause to allow sanity checking before continuing on (--pauseafter)

If configured, graphite will be sent a metric of the form events.deploy.{component} for each component deployed.

The rolling pin also features integration with Harold.

Setup

To install:

https://github.com/reddit/rollingpin.git
python setup.py install

Next, copy example.ini to /etc/rollingpin.ini or ~/.rollingpin.ini, modifying the hostsource to suit your environment.

For example, to set up an alias and deploy to 3 static hosts:

[hostsource]
provider = mock
hosts = host1 host2 host3

[aliases]
myhosts = host*

The hosts you are deploying to must have a local deploy script ready to be executed. You can use example-deploy.py as a starting point.

Once your deploy script is in place, update your configuration with its path:

[transport]
command = /usr/local/bin/deploy

When deploying, the deploy script will be called with the desired command on the command line.

For instance:

rollout -h myhosts -c foo

will call:

sudo /usr/local/bin/deploy foo

on the hosts matched by the myhosts alias.

Development

A Vagrantfile is included which sets up a testing environment that uses a mock hostsource and transport so that you can simulate deploys to non-existent hosts.

# launch the environment
host$ vagrant up
host$ vagrant ssh

# "deploy" to the full list of servers
rollingpin$ rollout test

# "deploy" to smaller subsets of servers
rollingpin$ rollout test -h common
rollingpin$ rollout test -h medium
rollingpin$ rollout test -h rare
rollingpin$ rollout test -h singular

# run the test suite
rollingpin$ cd rollingpin/
rollingpin$ python setup.py test

You can also run the test and lint suites in a Docker container:

docker build . -t rollingpin:test && docker run --rm rollingpin:test