Add timed incremental rollout to Auto DevOps

Auto DevOps deployment strategies now supports timed incremental
rollout. We are deprecating the usage of INCREMENTAL_ROLLOUT_ENABLED
environment variable in Auto DevOps template.

The new behavior will be driven by the INCREMENTAL_ROLLOUT_MODE variable
that can either be manual (same as INCREMENTAL_ROLLOUT_ENABLED) or
timed.

Rollout deployments will be executed using a 5 minute delay between each
job.

1 files changed, 47 insertions, 19 deletions

diff --git a/doc/topics/autodevops/index.md b/doc/topics/autodevops/index.md
index b5a9e469965..0d1ba3e8f9a 100644
--- a/doc/topics/autodevops/index.md
+++ b/doc/topics/autodevops/index.md
@@ -239,14 +239,19 @@ project's **Settings > CI/CD > Auto DevOps**.
 
 The available options are:
 
-- **Continuous deployment to production** - enables [Auto Deploy](#auto-deploy)
-  by setting the [`STAGING_ENABLED`](#deploy-policy-for-staging-and-production-environments) and
-  [`INCREMENTAL_ROLLOUT_ENABLED`](#incremental-rollout-to-production) variables
-  to false.
-- **Automatic deployment to staging, manual deployment to production** - sets the
+- **Continuous deployment to production**: Enables [Auto Deploy](#auto-deploy)
+  with `master` branch directly deployed to production.
+- **Continuous deployment to production using timed incremental rollout**: Sets the
+  [`INCREMENTAL_ROLLOUT_MODE`](#timed-incremental-rollout-to-production) variable
+  to `timed`, and production deployment will be executed with a 5 minute delay between
+  each increment in rollout.
+- **Automatic deployment to staging, manual deployment to production**: Sets the
   [`STAGING_ENABLED`](#deploy-policy-for-staging-and-production-environments) and
-  [`INCREMENTAL_ROLLOUT_ENABLED`](#incremental-rollout-to-production) variables
-  to true, and the user is responsible for manually deploying to staging and production.
+  [`INCREMENTAL_ROLLOUT_MODE`](#incremental-rollout-to-production) variables
+  to `1` and `manual`. This means:
+
+  - `master` branch is directly deployed to staging.
+  - Manual actions are provided for incremental rollout to production.
 
 ## Stages of Auto DevOps
 
@@ -609,7 +614,7 @@ also be customized, and you can easily use a [custom buildpack](#custom-buildpac
 | `DB_MIGRATE`                 | From GitLab 11.4, this variable can be used to specify the command to run to migrate the application's PostgreSQL database. It runs inside the application pod. |
 | `STAGING_ENABLED`            | From GitLab 10.8, this variable can be used to define a [deploy policy for staging and production environments](#deploy-policy-for-staging-and-production-environments). |
 | `CANARY_ENABLED`             | From GitLab 11.0, this variable can be used to define a [deploy policy for canary environments](#deploy-policy-for-canary-environments). |
-| `INCREMENTAL_ROLLOUT_ENABLED`| From GitLab 10.8, this variable can be used to enable an [incremental rollout](#incremental-rollout-to-production) of your application for the production environment. |
+| `INCREMENTAL_ROLLOUT_MODE`| From GitLab 11.4, this variable, if present, can be used to enable an [incremental rollout](#incremental-rollout-to-production) of your application for the production environment.<br/>Set to: <ul><li>`manual`, for manual deployment jobs.</li><li>`timed`, for automatic rollout deployments with a 5 minute delay each one.</li></ul> |
 | `TEST_DISABLED`              | From GitLab 11.0, this variable can be used to disable the `test` job. If the variable is present, the job will not be created. |
 | `CODE_QUALITY_DISABLED`       | From GitLab 11.0, this variable can be used to disable the `codequality` job. If the variable is present, the job will not be created. |
 | `SAST_DISABLED`              | From GitLab 11.0, this variable can be used to disable the `sast` job. If the variable is present, the job will not be created. |
@@ -730,9 +735,8 @@ to use an incremental rollout to replace just a few pods with the latest code.
 This will allow you to first check how the app is behaving, and later manually
 increasing the rollout up to 100%.
 
-If `INCREMENTAL_ROLLOUT_ENABLED` is defined in your project (e.g., set
-`INCREMENTAL_ROLLOUT_ENABLED` to `1` as a secret variable), then instead of the
-standard `production` job, 4 different
+If `INCREMENTAL_ROLLOUT_MODE` is set to `manual` in your project, then instead
+of the standard `production` job, 4 different
 [manual jobs](../../ci/pipelines.md#manual-actions-from-the-pipeline-graph)
 will be created:
 
@@ -756,21 +760,45 @@ environment page.
 Below, you can see how the pipeline will look if the rollout or staging
 variables are defined.
 
-- **Without `INCREMENTAL_ROLLOUT_ENABLED` and without `STAGING_ENABLED`**
+Without `INCREMENTAL_ROLLOUT_MODE` and without `STAGING_ENABLED`:
+
+![Staging and rollout disabled](img/rollout_staging_disabled.png)
+
+Without `INCREMENTAL_ROLLOUT_MODE` and with `STAGING_ENABLED`:
 
-    ![Staging and rollout disabled](img/rollout_staging_disabled.png)
+![Staging enabled](img/staging_enabled.png)
 
-- **Without `INCREMENTAL_ROLLOUT_ENABLED` and with `STAGING_ENABLED`**
+With `INCREMENTAL_ROLLOUT_MODE` set to `manual` and without `STAGING_ENABLED`:
 
-    ![Staging enabled](img/staging_enabled.png)
+![Rollout enabled](img/rollout_enabled.png)
 
-- **With `INCREMENTAL_ROLLOUT_ENABLED` and without `STAGING_ENABLED`**
+With `INCREMENTAL_ROLLOUT_MODE` set to `manual` and with `STAGING_ENABLED`
+
+![Rollout and staging enabled](img/rollout_staging_enabled.png)
+
+CAUTION: **Caution:**
+Before GitLab 11.4 this feature was enabled by the presence of the
+`INCREMENTAL_ROLLOUT_ENABLED` environment variable.
+This configuration is deprecated and will be removed in the future.
+
+#### Timed incremental rollout to production **[PREMIUM]**
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ee/issues/7545) in GitLab 11.4.
+
+TIP: **Tip:**
+You can also set this inside your [project's settings](#deployment-strategy).
 
-    ![Rollout enabled](img/rollout_enabled.png)
+This configuration based on
+[incremental rollout to production](#incremental-rollout-to-production).
 
-- **With `INCREMENTAL_ROLLOUT_ENABLED` and with `STAGING_ENABLED`**
+Everything behaves the same way, except:
 
-    ![Rollout and staging enabled](img/rollout_staging_enabled.png)
+- It's enabled by setting the `INCREMENTAL_ROLLOUT_MODE` variable to `timed`.
+- Instead of the standard `production` job, the following jobs with a 5 minute delay between each are created:
+    1. `timed rollout 10%`
+    1. `timed rollout 25%`
+    1. `timed rollout 50%`
+    1. `timed rollout 100%`
 
 ## Currently supported languages