Unit 1: Introduction to GitLab

Valentin DespaMarch 2, 2022About 6 min

Unit 1: Introduction to GitLab 관련

GitLab CI/CD can automatically build, test, deploy, and monitor your applications. We just published a full course on the freeCodeCamp.org YouTube channel that will teach you how to use GitLab CI. Valentin Despa developed this course. Valentin is an ...

DevOps with GitLab CI Course

Welcome

This course is for people new to DevOps who want to use GitLab to build, test and deploy their software
You will get hands-on experience building pipelines with GitLab CI and deploying software to AWS

Valentin Despa | @vdespa

Learn more about agile software development using tools such as Postman for API testing, Gitlab CI for supporting your DevOps cycle.

Your first GitLab project

we will be using GitLab.com in this course
create a free GitLab.com account
by default, you will get a free trial, and your account will be downgraded to a free one after 30 days
change the theme: [Profile] > [Preferences] > [Syntax highlighting theme] > [Monokai]
Enable Render whitespace characters in the Web IDE
GitLab CI pipelines are defined in a file called .gitlab-ci.yml

test:
  script: echo "Hello world"

to run your pipeline using the GitLab.com infrastructure, you need to verify your account with a credit card
validation troubleshooting:
- Validation is stuck. Nothing happens. If the interface is stuck or loading after 2-3 minutes of waiting, open a new tab and return to your main project page. If you don't see the message that you need to validate your account, it could mean that the validation was successful.

📚 Resources

Your first pipeline

when we build and ship software, we need to follow a series of steps
we define the GitLab CI pipeline using YAML
a job can execute one or multiple commands
mkdir build - creates a new folder called build
touch file.txt - creates a new file called file.txt
>> is called a redirection operator and appends the output from a previous command to a file
cat can be used for displaying the contents of a file
use Linux Alpine for this job because it is a very lightweight distribution
if no stage is defined in the job config, the test stage will be assigned
a pipeline is composed of a series of jobs organized in stages

Pipeline after this lecture

.gitlab-ci.yml

build laptop:
  image: alpine
  script: 
    - echo "Building a laptop"
    - mkdir build
    - touch build/computer.txt
    - echo "Mainboard" >> build/computer.txt
    - cat build/computer.txt
    - echo "Keyboard" >> build/computer.txt
    - cat build/computer.txt

Help, my pipeline is not working

here are some common mistakes that lead to errors in the jobs:
- no space after -, like -echo "Foo"
- bad indentation
- forgetting to add column : after stages: , build: , script:

📚 Resources

Top 10 Most Common Errors In GitLab CI Pipelines

What is YAML?

you need to know some YAML basics to write GitLab CI pipelines
YAML is somewhat similar to JSON or XML
XML, JSON and YAML, and human-readable data interchange formats
YAML is being often used for storing configurations

What is a shell?

we typically run commands such as echo, touch, mkdir, cat and so on through a command-line interface or CLI
to automate the building & releasing of software, we rely on tools that have no UI, so we need to use the CLI

📚 Resources

How to setup a Linux environment on Windows

GitLab architecture

at a minimum, the GitLab architecture contains the GitLab Server (also known as the coordinator) and a GitLab Runner
the GitLab server manages the execution of the pipeline and its jobs and stores the results
when a job needs to be executed, the GitLab server will find a runner to run the job
a runner is a simple program that executes a job
a working GitLab CI setup must have at least one runner, but there are often more of them to help distribute the load
there can also be specific runners that have a particular software or hardware configuration (this is outside of the scope of this course)
this is a simplified overview of the steps involved when a job is executed:
- the GitLab server (coordinator) locates a GitLab Runner and sends instructions for running the job
- the GitLab Runner will pull the Docker image specified in the job configuration (or the default image if no Docker image is specified)
- the GitLab Runner will start the Docker container
- the GitLab Runner will get the files stored in the Git repository
- the GitLab Runner run the commands from the script keyword inside the Docker container
- the GitLab Runner report back to the GitLab server (coordinator) the results of the job execution
- the GitLab Runner will terminate the Docker container

Docker in 100 Seconds

📚 Resources

What is Docker

Pipeline stages

by default, a job will be assigned to the Test stage
if two or more jobs belong to the same stage, they will be executed in parallel
the stages: keyword allows us to define the stages of the pipeline
the keyword stage: allows us to associate a job with a stage

Pipeline after this lecture

.gitlab-ci.yml

stages:
  - build
  - test

build laptop:
  image: alpine
  stage: build
  script: 
    - echo "Building a laptop"
    - mkdir build
    - touch build/computer.txt
    - echo "Mainboard" >> build/computer.txt
    - cat build/computer.txt
    - echo "Keyboard" >> build/computer.txt

test laptop:
  image: alpine
  stage: test
  script:
    - test -f build/computer.txt

Why do pipelines fail?

CLI programs indicate if their execution was successful or not by returning an exit code
an exit code 0 will indicate that a program has been executed successfully
any other exit code, which can be from 1 to 255, indicates failure
if GitLab detects a non-zero exit code, the job execution stops
Highly important tip: reading the job logs from top to bottom is KEY to understanding WHY a job has failed

Job artifacts

every job is executed in a separate container, so by default, no files are shared
to save the build results, we need to define the file(s) or folders as artifacts
in GitLab, we do this by using the artifacts keyword:

build laptop:
  ...
  artifacts:
    paths:
      - build

Pipeline after this lecture

.gitlab-ci.yml

stages:
  - build
  - test

build laptop:
  image: alpine
  stage: build
  script: 
    - echo "Building a laptop"
    - mkdir build
    - touch build/computer.txt
    - echo "Mainboard" >> build/computer.txt
    - cat build/computer.txt
    - echo "Keyboard" >> build/computer.txt
  artifacts:
    paths:
      - build

test laptop:
  image: alpine
  stage: test
  script:
    - test -f build/computer.txt

Testing the build

our goal is to automate both the build process and the test process
currently, we are only testing the content of the file by downloading the job artifacts or by using the cat command
to automate the testing process, we will use the grep command
grep allows us to search for a specific string in a file.

        - grep "Display" build/computer.txt

tests play a very important role in automation
you need to "test" the tests, to ensure that they will fail if needed

Variables

we prefer to use variables instead of repeating a string in the pipeline configuration
variables can be defined in scripts or using the variables: keyword
to reference the variable, we use the dollar sign before it

variables:
  BUILD_FILE_NAME: laptop.txt

variables can be defined locally in the job or globally for all jobs
when using spaces or some special characters, you may need to put the entire value between quotes

What is DevOps

DevOps is not a standard and does not have an universally agreed definition
DevOps is not a standard or a tool, but a set of practices
DevOps uses automation to that help us build successful Products
DevOps requires a different mindset and works really well with Agile & Scrum

📚 Resources

Introduction to Agile & Scrum