Deploy when GitHub is unavailable
Public GitHub (application code)
Many of the Git repositories which make up GOV.UK are hosted on public GitHub. We may need to deploy changes at any time, and GitHub.com is a Software as a Service (SaaS) product which is not guaranteed to be available.
If GitHub is unavailable, we lose:
- Access to our primary code repository
- The ability to authenticate with Jenkins, as it makes use of GitHub groups
We mirror all our repositories to AWS CodeComit every two hours using the
govuk-repo-mirror scripts. This is run from the
Mirror_Repositories CI job
In the event of Github being down, we can deploy the code from AWS CodeCommit repos. This requires help from a GOV.UK AWS admin.
Deploying from AWS CodeCommit
Use the normal deployment job but check the box to deploy from AWS CodeCommit.
Making changes to code in AWS CodeCommit before deployment
GOV.UK AWS admin users can give access to developers who need to make changes to the code before deployment. This may be necessary if we need to work in private, for example to fix a security vulnerability without disclosing it to the public. To do this, push to a new branch on AWS CodeCommit and then deploy that code.
Authenticating with Jenkins
If GitHub.com is down, we will not be able to log in to Jenkins.
In this scenario, Jenkins security should be disabled to enable deployment:
- SSH to the Jenkins Deploy instance:
- Disable Puppet:
govuk_puppet -r "Emergency Jenkins deploy" --disable
- Edit the Jenkins configuration file:
sudo vim /var/lib/jenkins/config.xml
- Restart Jenkins:
sudo service jenkins restart
- Browse to the Jenkins UI and begin the deployment process
- When completed, enable and run Puppet on the instance:
govuk_puppet --enable && govuk_puppet --test
Note that once security is disabled, anyone on GDS trusted IPs will be able to deploy to that environment. This will bypass protection for Production - do not leave Production without security for any longer than necessary.
See the Jenkins documentation for further details.
Simulating a GitHub outage on 2ndline
You can game an outage of GitHub.com by modifying your local hosts file.
sudo vi /etc/hosts
Don’t forget to remove it afterwards!
More about Deployment
- Add a deployment dashboard for an application
- Block apps from being deployed
- Deploy an application to GOV.UK
- Deploy fixes for a security vulnerability
- Deploy Puppet
- Fall back to the static mirrors
- Handle encrypted hieradata
- Monitor your app during deployment
- Restart an application
- Retire an application
- Run a rake task
- Set up a new Rails app
- Set up Heroku review apps for pull requests
- Switch an app off