Commit d53bb7c1 authored by Marcel Amirault's avatar Marcel Amirault

Merge branch 'sselhorn-redo-ci-concepts' into 'master'

Edited for style and clarity

See merge request gitlab-org/gitlab!54396
parents 40bc1771 77f700f0
......@@ -10,7 +10,7 @@ type: index
# GitLab CI/CD **(FREE)**
GitLab CI/CD is a tool built into GitLab for software development
through the [continuous methodologies](introduction/index.md#introduction-to-cicd-methodologies):
through the [continuous methodologies](introduction/index.md):
- Continuous Integration (CI)
- Continuous Delivery (CD)
......@@ -57,7 +57,7 @@ the following documents:
- [Get started with GitLab CI/CD](quick_start/index.md).
- [Fundamental pipeline architectures](pipelines/pipeline_architectures.md).
- [GitLab CI/CD basic workflow](introduction/index.md#basic-cicd-workflow).
- [GitLab CI/CD basic workflow](introduction/index.md#gitlab-cicd-workflow).
- [Step-by-step guide for writing `.gitlab-ci.yml` for the first time](../user/project/pages/getting_started/pages_from_scratch.md).
If you're migrating from another CI/CD tool, check out our handy references:
......
......@@ -6,122 +6,112 @@ description: "An overview of Continuous Integration, Continuous Delivery, and Co
type: concepts
---
# Introduction to CI/CD concepts **(FREE)**
# CI/CD concepts **(FREE)**
This document introduces the concepts of Continuous Integration,
Continuous Delivery, Continuous Deployment, and GitLab CI/CD.
With the continuous method of software development, you continuously build,
test, and deploy iterative code changes. This iterative process helps reduce
the chance that you develop new code based on buggy or failed previous versions.
With this method, you strive to have less human intervention or even no intervention at all,
from the development of new code until its deployment.
The three primary approaches for the continuous method are:
- [Continuous Integration](#continuous-integration)
- [Continuous Delivery](#continuous-delivery)
- [Continuous Deployment](#continuous-deployment)
NOTE:
Out-of-the-box management systems can decrease hours spent on maintaining toolchains by 10% or more.
Watch our ["Mastering continuous software development"](https://about.gitlab.com/webcast/mastering-ci-cd/)
webcast to learn about continuous methods and how the GitLab built-in CI can help you simplify and scale software development.
webcast to learn about continuous methods and how built-in GitLab CI/CD can help you simplify and scale software development.
> - <i class="fa fa-youtube-play youtube" aria-hidden="true"></i>&nbsp;Learn how to [configure CI/CD](https://www.youtube.com/embed/opdLqwz6tcE).
> - [Make the case for CI/CD in your organization](https://about.gitlab.com/compare/github-actions-alternative/).
> - <i class="fa fa-youtube-play youtube" aria-hidden="true"></i>&nbsp;Learn how [Verizon reduced rebuilds](https://about.gitlab.com/blog/2019/02/14/verizon-customer-story/)
> from 30 days to under 8 hours with GitLab.
## Introduction to CI/CD methodologies
The continuous methodologies of software development are based on
automating the execution of scripts to minimize the chance of
introducing errors while developing applications. They require
less human intervention or even no intervention at all, from the
development of new code until its deployment.
It involves continuously building, testing, and deploying code
changes at every small iteration, reducing the chance of developing
new code based on bugged or failed previous versions.
There are three main approaches to this methodology, each of them
to be applied according to what best suits your strategy.
### Continuous Integration
## Continuous Integration
Consider an application that has its code stored in a Git
repository in GitLab. Developers push code changes every day,
multiple times a day. For every push to the repository, you
can create a set of scripts to build and test your application
automatically, decreasing the chance of introducing errors to your app.
automatically. These scripts help decrease the chances that you introduce errors in your application.
This practice is known as [Continuous Integration](https://en.wikipedia.org/wiki/Continuous_integration);
for every change submitted to an application - even to development branches -
it's built and tested automatically and continuously, ensuring the
introduced changes pass all tests, guidelines, and code compliance
standards you established for your app.
This practice is known as [Continuous Integration](https://en.wikipedia.org/wiki/Continuous_integration).
Each change submitted to an application, even to development branches,
is built and tested automatically and continuously. These tests ensure the
changes pass all tests, guidelines, and code compliance
standards you established for your application.
[GitLab itself](https://gitlab.com/gitlab-org/gitlab-foss) is an
example of using Continuous Integration as a software
development method. For every push to the project, there's a set
of scripts the code is checked against.
[GitLab itself](https://gitlab.com/gitlab-org/gitlab) is an
example of a project that uses Continuous Integration as a software
development method. For every push to the project, a set
of checks run against the code.
### Continuous Delivery
## Continuous Delivery
[Continuous Delivery](https://continuousdelivery.com/) is a step
beyond Continuous Integration. Your application is not only
built and tested at every code change pushed to the codebase,
but, as an additional step, it's also deployed continuously, though
the deployments are triggered manually.
beyond Continuous Integration. Not only is your application
built and tested each time a code change is pushed to the codebase,
the application is also deployed continuously. However, with continuous
delivery, you trigger the deployments manually.
This method ensures the code is checked automatically but requires
Continuous Delivery checks the code automatically, but it requires
human intervention to manually and strategically trigger the deployment
of the changes.
### Continuous Deployment
## Continuous Deployment
[Continuous Deployment](https://www.airpair.com/continuous-deployment/posts/continuous-deployment-for-practical-people)
is also a further step beyond Continuous Integration, similar to
is another step beyond Continuous Integration, similar to
Continuous Delivery. The difference is that instead of deploying your
application manually, you set it to be deployed automatically. It does
not require human intervention at all to have your application
deployed.
application manually, you set it to be deployed automatically.
Human intervention is not required.
## Introduction to GitLab CI/CD
## GitLab CI/CD
[GitLab CI/CD](../quick_start/index.md) is a powerful tool built into GitLab that allows you
to apply all the continuous methods (Continuous Integration,
Delivery, and Deployment) to your software with no third-party
application or integration needed.
[GitLab CI/CD](../quick_start/index.md) is the part of GitLab that you use
for all of the continuous methods (Continuous Integration,
Delivery, and Deployment). With GitLab CI/CD, you can test, build,
and publish your software with no third-party application or integration needed.
<i class="fa fa-youtube-play youtube" aria-hidden="true"></i>
For an overview, see [Introduction to GitLab CI](https://www.youtube.com/watch?v=l5705U8s_nQ&t=397) from a recent GitLab meetup.
For an overview, see [Introduction to GitLab CI/CD](https://www.youtube.com/watch?v=l5705U8s_nQ&t=397) from an April 2020 GitLab meetup.
### Basic CI/CD workflow
### GitLab CI/CD workflow
Consider the following example for how GitLab CI/CD fits in a
common development workflow.
GitLab CI/CD fits in a common development workflow.
Assume that you have discussed a code implementation in an issue
and worked locally on your proposed changes. After you push your
commits to a feature branch in a remote repository in GitLab,
the CI/CD pipeline set for your project is triggered. By doing
so, GitLab CI/CD:
You can start by discussing a code implementation in an issue
and working locally on your proposed changes. Then you can push your
commits to a feature branch in a remote repository that's hosted in GitLab.
The push triggers the CI/CD pipeline for your project. Then, GitLab CI/CD:
- Runs automated scripts (sequentially or in parallel) to:
- Build and test your app.
- Preview the changes per merge request with Review Apps, as you
would see in your `localhost`.
- Build and test your application.
- Preview the changes in a Review App, the same as you
would see on your `localhost`.
After you're happy with your implementation:
After the implementation works as expected:
- Get your code reviewed and approved.
- Merge the feature branch into the default branch.
- GitLab CI/CD deploys your changes automatically to a production environment.
- And finally, you and your team can easily roll it back if something goes wrong.
If something goes wrong, you can roll back your changes.
![GitLab workflow example](img/gitlab_workflow_example_11_9.png)
GitLab CI/CD is capable of doing a lot more, but this workflow
exemplifies the ability of GitLab to track the entire process,
without the need for an external tool to deliver your software.
And, most usefully, you can visualize all the steps through
the GitLab UI.
This workflow shows the major steps in the GitLab process.
You don't need any external tools to deliver your software and
you can visualize all the steps in the GitLab UI.
### A deeper look into the CI/CD workflow
If we take a deeper look into the basic workflow, we can see
If you look deeper into the workflow, you can see
the features available in GitLab at each stage of the DevOps
lifecycle, as shown in the illustration below.
lifecycle.
![Deeper look into the basic CI/CD workflow](img/gitlab_workflow_example_extended_v12_3.png)
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