| [Creating and using CI/CD pipelines](pipelines.md) | Understand, visualize, create, and use CI/CD pipelines. |
| [CI/CD Variables](variables/README.md) | How environment variables can be configured and made available in pipelines. |
| [Where variables can be used](variables/where_variables_can_be_used.md) | A deeper look into where and how CI/CD variables can be used. |
| [User](../user/permissions.md#gitlab-cicd-permissions) and [job](../user/permissions.md#job-permissions) permissions | Learn about the access levels a user can have for performing certain CI actions. |
| [CI/CD Variables](variables/README.md) | Configuring and using environment variables in pipelines. |
| [Where variables can be used](variables/where_variables_can_be_used.md) | Where and how CI/CD variables can be used. |
| [User](../user/permissions.md#gitlab-cicd-permissions) and [job](../user/permissions.md#job-permissions) permissions | User access levels for performing certain CI actions. |
| [Job artifacts](../user/project/pipelines/job_artifacts.md) | Using the output of jobs. |
| [Cache dependencies in GitLab CI/CD](caching/index.md) | Speed up pipelines using caching. |
| [Using Git submodules with GitLab CI](git_submodules.md) | How to run your CI jobs when using Git submodules. |
| [Pipelines for merge requests](merge_request_pipelines/index.md) | Create pipelines specifically for merge requests. |
| [Using SSH keys with GitLab CI/CD](ssh_keys/README.md) | Use SSH keys in your build environment. |
| [Triggering pipelines through the API](triggers/README.md) | Use the GitLab API to trigger a pipeline. |
| [Pipeline schedules](../user/project/pipelines/schedules.md) | Trigger pipelines on a schedule. |
| [Connecting GitLab with a Kubernetes cluster](../user/project/clusters/index.md) | Integrate one or more Kubernetes clusters to your project. |
| [ChatOps](chatops/README.md) | Trigger CI jobs from chat, with results sent back to the channel. |
| [Interactive web terminals](interactive_web_terminal/index.md) | Open an interactive web terminal to debug the running jobs. |
| [Review Apps](review_apps/index.md) | Configure GitLab CI/CD to preview code changes in a per-branch basis. |
| [Optimizing GitLab for large repositories](large_repositories/index.md) | Useful tips on how to optimize GitLab and GitLab Runner for big repositories. |
| [Deploy Boards](https://docs.gitlab.com/ee/user/project/deploy_boards.html)**[PREMIUM]** | Check the current health and status of each CI/CD environment running on Kubernetes. |
| [GitLab CI/CD for external repositories](https://docs.gitlab.com/ee/ci/ci_cd_for_external_repos/index.html)**[PREMIUM]** | Get the benefits of GitLab CI/CD combined with repositories in GitHub and BitBucket Cloud. |
> - [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/21971) in GitLab 8.12. Further additions were made in GitLab 8.13 and 8.14.
> - Inspired by [Heroku's Review Apps](https://devcenter.heroku.com/articles/github-integration-review-apps), which itself was inspired by [Fourchette](https://github.com/rainforestapp/fourchette).
For a video introduction to Review Apps, see [8.14 Webcast: Review Apps & Time Tracking Beta (EE) - GitLab Release](https://www.youtube.com/watch?v=CteZol_7pxo).
## Overview
Review Apps are a collaboration tool that takes the hard work out of providing an environment to showcase product changes.
## Introduction
Review Apps:
- Provide an automatic live preview of changes made in a feature branch by spinning up a dynamic environment for your merge requests.
Reviewing anything, from performance to interface changes, becomes much easier with a live environment and so Review Apps can make a large impact on your development flow.
In the above example:
## What are Review Apps?
- A Review App is built every time a commit is pushed to`topic branch`.
- The reviewer fails two reviews before passing the third review.
- Once the review as passed, `topic branch` is merged into `master` where it's deploy to staging.
- After been approved in staging, the changes that were merged into `master` are deployed in to production.
A Review App is a mapping of a branch with an [environment](../environments.md). The following is an example of a merge request with an environment set dynamically.
### How Review Apps work
A Review App is a mapping of a branch with an [environment](../environments.md).
Access to the Review App is made available as a link on the [merge request](../../user/project/merge_requests.md) relevant to the branch.
The following is an example of a merge request with an environment set dynamically.
In this example, you can see a branch was:
In this example, a branch was:
- Successfully built.
- Deployed under a dynamic environment that can be reached by clicking on the **View app** button.
## How do Review Apps work?
The basis of Review Apps in GitLab is [dynamic environments](../environments.md#configuring-dynamic-environments), which allow you to dynamically create a new environment for each branch.
Access to the Review App is made available as a link on the [merge request](../../user/project/merge_requests.md) relevant to the branch. Review Apps enable you to review all changes proposed by the merge request in live environment.
## Use cases
Some supported use cases include the:
- Simple case of deploying a simple static HTML website.
- More complicated case of an application that uses a database. Deploying a branch on a temporary instance and booting up this instance with all required software and services automatically on the fly is not a trivial task. However, it is possible, especially if you use Docker or a configuration management tool like Chef, Puppet, Ansible, or Salt.
Review Apps usually make sense with web applications, but you can use them any way you'd like.
## Implementing Review Apps
Implementing Review Apps depends on your:
- Technology stack.
- Deployment process.
### Prerequisite Knowledge
To get a better understanding of Review Apps, review documentation on how environments and deployments work. Before you implement your own Review Apps:
1. Learn about [environments](../environments.md) and their role in the development workflow.
1. Learn about [CI variables](../variables/README.md) and how they can be used in your CI jobs.
1. Explore the [`environment` syntax](../yaml/README.md#environment) as defined in `.gitlab-ci.yml`. This will become a primary reference.
1. Additionally, find out about [manual actions](../environments.md#configuring-manual-deployments) and how you can use them to deploy to critical environments like production with the push of a button.
1. Follow the [example tutorials](#examples). These will guide you through setting up infrastructure and using Review Apps.
### Configuring dynamic environments
Configuring Review Apps dynamic environments depends on your technology stack and infrastructure.
For more information, see [dynamic environments](../environments.md#configuring-dynamic-environments) documentation to understand how to define and create them.
### Creating and destroying Review Apps
Creating and destroying Review Apps is defined in `.gitlab-ci.yml` at a job level under the `environment` keyword.
## Configuring Review Apps
For more information, see [Introduction to environments and deployments](../environments.md).
Review Apps are built on [dynamic environments](../environments.md#configuring-dynamic-environments), which allow you to dynamically create a new environment for each branch.
### Adding Review Apps to your workflow
The process of adding Review Apps in your workflow is as follows:
The process of configuring Review Apps is as follows:
1. Set up the infrastructure to host and deploy the Review Apps.
1.[Install](https://docs.gitlab.com/runner/install/) and [configure](https://docs.gitlab.com/runner/commands/) a Runner to do deployment.
1. Set up a job in `.gitlab-ci.yml` that uses the [predefined CI environment variable](../variables/README.md)`${CI_COMMIT_REF_NAME}` to create dynamic environments and restrict it to run only on branches.
1. Optionally, set a job that [manually stops](../environments.md#stopping-an-environment) the Review Apps.
After adding Review Apps to your workflow, you follow the branched Git flow. That is:
### Examples
1. Push a branch and let the Runner deploy the Review App based on the `script` definition of the dynamic environment job.
1. Wait for the Runner to build and deploy your web application.
1. Click on the link that provided in the merge request related to the branch to see the changes live.
## Limitations
Check the [environments limitations](../environments.md#limitations).
## Examples
The following are example projects that use Review Apps with:
The following are example projects that demonstrate Review App configuration:
