139 lines
6.4 KiB
Markdown
139 lines
6.4 KiB
Markdown
---
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stage: Release
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group: Release
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info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
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type: concepts, howto
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---
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# Incremental rollouts with GitLab CI/CD **(FREE)**
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When rolling out changes to your application, it is possible to release production changes
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to only a portion of your Kubernetes pods as a risk mitigation strategy. By releasing
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production changes gradually, error rates or performance degradation can be monitored, and
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if there are no problems, all pods can be updated.
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GitLab supports both manually triggered and timed rollouts to a Kubernetes production system
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using Incremental Rollouts. When using Manual Rollouts, the release of each tranche
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of pods is manually triggered, while in Timed Rollouts, the release is performed in
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tranches after a default pause of 5 minutes.
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Timed rollouts can also be manually triggered before the pause period has expired.
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Manual and Timed rollouts are included automatically in projects controlled by
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[Auto DevOps](../../topics/autodevops/index.md), but they are also configurable through
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GitLab CI/CD in the `.gitlab-ci.yml` configuration file.
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Manually triggered rollouts can be implemented with your [Continuous Delivery](../introduction/index.md#continuous-delivery)
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methodology, while timed rollouts do not require intervention and can be part of your
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[Continuous Deployment](../introduction/index.md#continuous-deployment) strategy.
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You can also combine both of them in a way that the app is deployed automatically
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unless you eventually intervene manually if necessary.
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We created sample applications to demonstrate the three options, which you can
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use as examples to build your own:
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- [Manual incremental rollouts](https://gitlab.com/gl-release/incremental-rollout-example/blob/master/.gitlab-ci.yml)
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- [Timed incremental rollouts](https://gitlab.com/gl-release/timed-rollout-example/blob/master/.gitlab-ci.yml)
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- [Both manual and timed rollouts](https://gitlab.com/gl-release/incremental-timed-rollout-example/blob/master/.gitlab-ci.yml)
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## Manual Rollouts
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It is possible to configure GitLab to do incremental rollouts manually through `.gitlab-ci.yml`. Manual configuration
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allows more control over the this feature. The steps in an incremental rollout depend on the
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number of pods that are defined for the deployment, which are configured when the Kubernetes
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cluster is created.
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For example, if your application has 10 pods and a 10% rollout job runs, the new instance of the
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application is deployed to a single pod while the rest of the pods show the previous instance of the application.
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First we [define the template as manual](https://gitlab.com/gl-release/incremental-rollout-example/blob/master/.gitlab-ci.yml#L100-103):
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```yaml
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.manual_rollout_template: &manual_rollout_template
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<<: *rollout_template
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stage: production
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when: manual
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```
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Then we [define the rollout amount for each step](https://gitlab.com/gl-release/incremental-rollout-example/blob/master/.gitlab-ci.yml#L152-155):
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```yaml
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rollout 10%:
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<<: *manual_rollout_template
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variables:
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ROLLOUT_PERCENTAGE: 10
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```
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When the jobs are built, a **play** button appears next to the job's name. Select **play**
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to release each stage of pods. You can also rollback by running a lower percentage job. Once 100%
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is reached, you cannot roll back using this method. It is still possible to roll back by redeploying
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the old version using the **Rollback** button on the environment page.
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A [deployable application](https://gitlab.com/gl-release/incremental-rollout-example) is
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available, demonstrating manually triggered incremental rollouts.
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## Timed Rollouts
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Timed rollouts behave in the same way as manual rollouts, except that each job is defined with a
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delay in minutes before it deploys. Clicking the job reveals the countdown.
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It is possible to combine this functionality with manual incremental rollouts so that the job
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counts down and then deploys.
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First we [define the template as timed](https://gitlab.com/gl-release/timed-rollout-example/blob/master/.gitlab-ci.yml#L86-89):
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```yaml
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.timed_rollout_template: &timed_rollout_template
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<<: *rollout_template
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when: delayed
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start_in: 1 minutes
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```
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We can define the delay period using the `start_in` key:
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```yaml
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start_in: 1 minutes
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```
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Then we [define the rollout amount for each step](https://gitlab.com/gl-release/timed-rollout-example/blob/master/.gitlab-ci.yml#L97-101):
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```yaml
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timed rollout 30%:
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<<: *timed_rollout_template
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stage: timed rollout 30%
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variables:
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ROLLOUT_PERCENTAGE: 30
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```
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A [deployable application](https://gitlab.com/gl-release/timed-rollout-example) is
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available, [demonstrating configuration of timed rollouts](https://gitlab.com/gl-release/timed-rollout-example/blob/master/.gitlab-ci.yml#L86-95).
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## Blue-Green Deployment
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NOTE:
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As of GitLab 13.7, teams can leverage an Ingress annotation and [set traffic weight](../../user/project/canary_deployments.md#how-to-change-the-traffic-weight-on-a-canary-ingress-deprecated)
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as an alternative approach to the blue-green deployment strategy documented here.
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Also sometimes known as A/B deployment or red-black deployment, this technique is used to reduce
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downtime and risk during a deployment. When combined with incremental rollouts, you can
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minimize the impact of a deployment causing an issue.
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With this technique there are two deployments ("blue" and "green", but any naming can be used).
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Only one of these deployments is live at any given time, except during an incremental rollout.
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For example, your blue deployment can be currently active on production, while the
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green deployment is "live" for testing, but not deployed to production. If issues
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are found, the green deployment can be updated without affecting the production
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deployment (currently blue). If testing finds no issues, you switch production to the green
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deployment, and blue is now available to test the next release.
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This process reduces downtime as there is no need to take down the production deployment
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to switch to a different deployment. Both deployments are running in parallel, and
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can be switched to at any time.
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An [example deployable application](https://gitlab.com/gl-release/blue-green-example)
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is available, with a [`.gitlab-ci.yml` CI/CD configuration file](https://gitlab.com/gl-release/blue-green-example/blob/master/.gitlab-ci.yml)
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that demonstrates blue-green deployments.
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