# CI Setup for application

Let’s say we have a Node.js API that retrieves a list of books in a database. We can create a pipeline that pushes our code through three phases: build, test and deploy. A **pipeline** is a group of steps that are grouped by similar characteristics. With those phases our pipeline is defined by three types:

* **Project Pipeline**
* **Continuous Integration Pipeline**
* **Deploy Pipeline**

The **Project Pipeline** installs dependencies, runs linters and any scripts that deal with the code. The **Continuous Integration Pipeline** runs automated tests and builds a distributed version of the code. Finally, the **Deploy Pipeline** deploys code to a designated cloud provider and environment.

The steps that the three pipelines execute are called **jobs**. When you group a series of jobs by those characteristics it is called **stages.** Jobs are the basic building block for pipelines. They can be grouped together in stages and stages can be grouped together into pipelines. Here’s an example hierarchy of jobs, stages, and pipelines:

```
A.) Build
 i. Install NPM Dependencies
 ii. Run ES-Linter
 iii. Run Code-Minifier
B.) Test
 i. Run unit, functional and end-to-end test.
 ii. Run pkg to compile Node.js application
C.) Deploy
 i. Production
 1.) Launch EC2 instance on AWS
 ii. Staging
 1.) Launch on local development server
```

In this hierarchy, all three components are considered three different pipelines. The main bullets — build, test, and deploy are **stages** and each bullet under those sections are jobs. Let’s break this out into a GitLab CI/CD `yaml`file.

#### Using GitLab CI/CD <a href="#id-3c70" id="id-3c70"></a>

To use GitLab CI/CD, create a file called `.gitlab-ci.yml` at the root of the project in your GitLab repository and add the following `yaml`:

```
image: node:10.5.0
stages:
 — build
 — test
 — deploy
before_script:
 — npm install
```

As I mentioned earlier, GitLab CI/CD uses Runners to execute pipelines. We can define which operating system and predefined libraries we would want our Runner to be based off by using the `image` directive. In our instance, we will be using the latest version of Node.js for our Runner. The `stages`directive allows us to predefine a stage for the entire configuration. Jobs will be executed based off of the order listed in the `stages` directive. To learn more about stages you can view it [here](https://docs.gitlab.com/ee/ci/yaml/#stages). The `before_script` directive is used to run a command before all jobs.

Now let’s start with our job dedicated to the **Build** stage. We are going to call this job `build-min-code`. In this job we want it to install dependencies and minify the code. We can start this off with using the `script` directive. The `script`directive is a shell script that gets executed within the Runner. Then we are going to assign this job to the “build” stage. To assign a job to a stage, use the `stage`directive.

```
build-min-code:
  stage: build
  script:
    - npm install
    - npm run minifier
```

Now we have a job associated with our **Build** stage and we are going to do that for our **Test** stage. Our test job is going to be called `run-unit-test`and we are going to use the npm script in our API to run a test `npm test`.

```
run-unit-test:
  stage: test
  script:
    - npm run test
```

Finally, we are going to add a job to handle our **Deploy** stage: `deploy-production`, `deploy-staging`. In this instance, we are going to have two different jobs for deployment (staging and production). These jobs will reflect the same layout as our previous jobs but with a small change. Currently, all of our jobs are **automatically** set to be triggered on any code push or branch. We do not want to have that for when we deploy our code to staging and production. To prevent that from happening we use the `only` directive. The `only` directive defines the names of branches and tags for which the job will run. The job will look like the following:

```
deploy-staging:
 stage: deploy
 script:
   — npm run deploy-stage
 only:
   — develop
deploy-production:
 stage: deploy
 script:
   — npm run deploy-prod
 only:
   — master   
   
```

In our `deploy-staging` job, the Runner will only execute it if there was a change to the `develop` branch and for `deploy-production` the `master`branch. Here is a screenshot below that shows a code push made to the `master` branch.

![](https://cdn-images-1.medium.com/max/1600/1*_cdL-GKdhQs3UhCvDQU4ZQ.png)

From this image all three stages and jobs are triggered with the exception of `deploy-staging` since the code push was to the`master` branch. GitLab CI/CD comes with an intuitive interface to help show what jobs and stages are running and what errors are occurring in the midst of the build. Below is the final version of the `.gitlab-ci.yaml` file. If you wish to test this out yourself, here is the [link](https://gitlab.com/zh-examples/gitlabci-demo) to the example application.

```
image: node:10.5.0

stages:
  - build
  - test
  - deploy

before_script:
  - echo 'hello world'

build-dev-code:
  stage: build
  script:
    - npm install
  only:
    - develop

test-dev-code:
  stage: test
  script:
    - npm run test
  only:
    - develop

deploy-dev:
  stage: deploy
  script:
    - npm run deploy-dev
  only:
    - develop


build-qa-code:
  stage: build
  script:
    - npm install
  only:
    - master

test-qa-code:
  stage: test
  script:
    - npm run test
  only:
    - master

deploy-qa:
  stage: deploy
  script:
    - npm run deploy-qa
  only:
    - master    
```
