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Deployment

Deploy Puppet

Deploying a branch

Before merging your PR, it’s recommended that you deploy the change to Integration in order to test it works on real infrastructure. Go to the Deploy_Puppet job in Jenkins and click ‘Build with Parameters’. The TAG field should contain the name of the branch you wish to deploy.

Deploying a release

You can deploy Puppet to Staging and Production using the following steps:

  1. Deploy a newer version of govuk-puppet to staging by using the ‘Deploy to Staging (Carrenza)’ and ‘Deploy to Staging (AWS)’ buttons in the Release app after clicking on the release tag and reviewing the changes listed.
  2. You will either need to wait 30 minutes or read about convergence. You should monitor Icinga and Smokey, and test anything you’re concerned about.
  3. Repeat the above steps for Production.

Puppet is automatically deployed to integration by a combination of the integration-puppet-deploy job on Jenkins CI and Deploy Puppet job on Jenkins Deploy jobs.

WARNING

If you’re deploying a change to hiera.yml or hiera_aws.yml, you will need to restart the Puppet server on the Puppet Master machine, otherwise these changes will not be picked up.

To restart the server, run sudo service puppetserver restart.

Convergence

The deployment only pushes the new code to the Puppet Master. Each node runs a Puppet agent every 30 minutes (via cron), so it may be some time before the release takes effect. This has an implication on how quickly you can go from staging to production.

If you’d rather not wait and you’re able to safely determine from the diff what classes of machines the change will affect, you can use Fabric to force a run of Puppet. For example:

fab $environment class:frontend_lb class:backend_lb puppet

This will run in serial across the nodes so there is a reduced chance of downtime caused by a service restarting on all nodes of a given class at the same time. You should still be careful though, because some services take longer to restart than others.

Preventing service restarts

It may occassionally be neccessary to trick Puppet into not restarting a service, if it is a single point of failure and doing so would cause a brief outage, e.g. MySQL.

WARNING

This is not a “normal” procedure. You should only do this if you need to and you MUST have some plan for restarting the service in the near future so that it’s not inconsistent with its configuration.

  1. Disable normal Puppet runs on the affected nodes:
   fab $environment class:mysql_master puppet.disable:'Preventing service restart'
  1. Change the file content to match what Puppet wants it to be. If it’s a plain file you can probably apply the diff from git using sudo patch source.diff dest. If it’s a template then you may need to refer to an existing environment or figure it out yourself.
  2. Verify that Puppet won’t change the file or notify the service by running it in noop mode. You will need to provide a different lock path to bypass the disable:
   govuk_puppet --noop --test --agent_disabled_lockfile=/tmp/puppet.noop
  1. If you’re happy with the results then re-enable Puppet and run it again:
   fab $environment class:mysql_master puppet.enable puppet
  1. Schedule a time to actually restart the service if necessary.
This page was last reviewed on 25 August 2020. It needs to be reviewed again on 25 February 2021 by the page owner #govuk-developers .
This page was set to be reviewed before 25 February 2021 by the page owner #govuk-developers. This might mean the content is out of date.