DevOps Pipeline Automation with Google Cloud Build and Triggers

December 22, 2021

DevOps is a set of practices or stages that every application goes through before and after deployment which ensures continuous integration and deployment (CI/CD) of the application. The CI/CD pipeline automates the process for the deployment of code changes to the specified type of environment.

The Software Development Life Cycle (SDLC) in conjunction with the operations cycle makes the development and operations (known as DevOps).

Docker packages applications as Docker images and stores them into containers with their configurations defined within the DockerFile.

Both the Google Cloud Platform’s (GCP) Cloud Build and Container Registry are used to build and manage the built docker images.

Table of contents


To follow along with this tutorial with ease, one should have the following:

  • Have a basic understanding of Git repository and programming languages like Python.
  • Have installed Python.
  • Have installed an IDE or code editor, preferably Visual Studio Code.
  • A basic understanding of Docker.
  • A basic understanding of Flask.


In this tutorial, we will be learning how to automate DevOps pipelines using the GCP Cloud Build.

By reading this article, you will gain experience in:

  • Defining the stages of DevOps pipelines.
  • Making a repository for the application.
  • Creating a Python application.
  • Cloud Shell usages for testing.
  • Building the Docker images.
  • Using GCP Container Registry to manage images.
  • Processing automation with triggers.
  • Build changes testing.

Define the stages of DevOps pipelines

There are different stages involved in building pipelines from development to production.

The picture below describes all the pre-defined stages:

DevOps Stages

Let’s understand more about each stage:


Without a proper plan, no one can successfully develop an application. An adequate plan must be put in place before embarking on the journey of development.

This is the stage where the justifications shall be given to technology stacks and other things required.


Developers embark on the coding part after the requirements have been set in stage one. They will work on the application by collaborating through a single source of a repository.


In this stage, the application developed shall be packaged and built into images using the choice of a package manager like Docker.

The application will also be shipped into containers with the configurations file required for its start-up.


A series of tests will run through the application for better performance. Developers perform various types of application testing like unit testing, smoke testing, integration testing, and so on.

Other tests can be accomplished by the testers and quality assurance engineers. Selenium is the most popular continuous testing framework used in the industry.


This is where the stage of continuous integration begins. This stage will be repeated countless times whenever there is any update in the application.

The popular tools used for this are Jenkins, GitHub Actions, Team City, and many more.


An application that passed the continuous integration stage will proceed to the deployment stage. Staging will be the first thing before deployment using tools like Ansible, Puppet, or Chef.


The actual deployment starts in this stage using tools like terraform etc. The refined application will then be deployed and its operations will be monitored.


The deployed application will be monitored in terms of performance. Logs will be generated while it is monitored.

All of these CI/CD stages can be done via the cloud.

In this tutorial, we will learn more about these pipelines by building a simple application. By building, you will understand the development and operation parts of the DevOps architecture.

Make a repository for the application

First, you will create a free trial account on the Google Cloud Platform console. This free account will run through the span of a year with a sum of the amount for billing purposes.

Click on this link to create a new account.

Having successfully created a new account, you will be redirected to the dashboard page as shown:

Cloud Console Dashboard

Before any resources can be consumed in the cloud, a project must be created.

You can create the project by clicking on the dropdown menu in the navigation bar. Then, tap on the New Project button inside the pop-up page.

Note that every project created is under an organization. A project has both name and an automatically generated unique ID.

Furthermore, we will make use of the cloud source repository provided.

The cloud source repository acts as a store for the development code. This service is very similar to that of platforms like Github, Gitlab, Bitbucket, and more.

Eventually, you will create a build trigger that starts a continuous integration pipeline when code is pushed to it.

To create a repository in the source, follow the steps below:

  • In the cloud console menu, click Source Repositories.
  • Click on the button Add repository.
  • Select Create a new repository and click Continue.
  • Name the repository as devops-repo.
  • Select your current project ID from the list.
  • And, click Create.

The image below shows the created repository. Refresh the page to verify the codes that were uploaded.

Source Repository

  • Return to the cloud console dashboard, and click Activate Cloud Shell in the top menu bar.

For the first time, you would have to set your project in the shell using the following command:

gcloud config set project 
  • If prompted, click Continue.
  • Enter the following commands in the cloud shell to create a new folder learning-devops, and clone the created repository created:
mkdir learning-devops
cd learning-devops
gcloud source repos clone devops-repo

Note: The cloned repository can be seen in the Source Repository section, under the navigation menu.

Create a Python application

We will create a Flask application for demonstration. The application will be good enough to test the pipeline that you are going to build.

Below is the set of instructions for the application:

  • In the cloud shell, click Open Editor to open the code editor.
  • Select the learning-devops > devops-repo folder in the explorer tree on the left.
  • Click New File and name it

Paste the following into the file you just created:

from flask import Flask, render_template, request

app = Flask(__name__)

def main():
    model = {"title": "Hello DevOps Fans."}
    return render_template('index.html', model=model)

if __name__ == "__main__":'', port=8080, debug=True, threaded=True)
  • Save your changes.
  • Right-click on the devops-repo folder and add a new folder called templates.
  • In that folder, add a new file called layout.html with the folling code:
<!doctype html>
<html lang="en">
    <div class="container">
        {% block content %}{% endblock %}
  • Also in the templates folder, add another file named index.html with the following code:
{% extends "layout.html" %}
{% block content %}
{% endblock %}

Here, we created a simple Flask application that renders an index.html with a title “Hello DevOps Fans.”.

  • In Python, the application dependencies are managed using the pip package manager.
  • Now, you will add a file that lists the requirements for this application.
  • In the devops-repo folder, create a new file requirements.txt with the below content:
  • In cloud shell, type the following code:
cd ~/learning-devops/devops-repo
git add --all
  • Then, commit and push these changes to the repository, after entering your credentials:
git config -g "your-mail-here"
git config -g "Your Name Here"

git commit -a -m "Initial Commit"
git push origin master

On refreshing the repositories page, you must see the same files that we created locally.

Cloud shell usages for testing

The application can be tested using Cloud Shell by following the below steps:

  • Back in Cloud Shell, make sure you are in your application’s root folder, and then install the Flask framework using pip:
cd ~/learning-devops/devops-repo
sudo pip3 install -r requirements.txt
  • To run the program, type:

Note: The server is configured to run on port 8080.

  • To see the program running, click Web Preview in the toolbar of Cloud Shell. Then, click Preview on port 8080.

The program would be displayed in a new browser tab as shown:

Result of deployment

  • To stop the program, return to the Cloud Console and press Ctrl+C in Cloud Shell.
  • In the code editor, expand the learning-devops/devops-repo folder in the explorer pane on the left, and open the file.
  • Change the title to something else as shown below:
def main():
    model={"title": "Whatever you want."}
    return render_template('index.html', model=model)
  • On the Code Editor toolbar under the File menu, click Save to save your changes.
  • Navigate to the Cloud Shell and commit the changes to the repository as shown:
cd ~/gcp-course/devops-repo
git commit -a -m "committing another changes"
  • Push your changes to the cloud using the following command:
git push origin master
  • Return to the Source Repositories page and refresh the repository to verify that your changes were uploaded.

Building the Docker images

The first step to using Docker is to create a file called DockerFile.

This file defines how a Docker container is made. It also describes and contains instructions for installing various dependencies required by the application.

The following are the set of commands required by our flask application inside the DockerFile:

  • In the Cloud shell code editor, expand the learning-devops/devops-repo folder. Click on New File and the name it DockerFile.
  • Specify the Python image as below at the topmost of the file.
FROM python:3.7
COPY . .

These lines copy the source code from the current folder into the /app folder.

RUN pip install gunicorn 
RUN pip install -r requirements.txt

This uses the pip package manager to install the requirements of the Python application into the container.

Gunicorn is a Python web server that will be used to run the web app.

CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 main:app

The environment variable sets the port as 80. The last line runs the web app using the gunicorn web server.

  • Ensure that the complete DockerFile looks as shown here:
FROM python:3.7
COPY . .
RUN pip install gunicorn 
RUN pip install -r requirements.txt
CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 main:app

Manage Docker images with Cloud Build and Container Registry

The Docker image would be created and stored in the registry. This image would then be wrapped up with the start-up commands in the container.

The Cloud Build is the infrastructure provided by the GCP for building Docker images. While the Container Registry stores the images built and can be accessed from there.

Note: The Docker image can also be stored in the Docker Hub.

  • Return to Cloud Shell and navigate to the file below:
cd ~/learning-devops/devops-repo
  • The Cloud Shell with environment variable DEVSHELL_PROJECT_ID contains the current project ID. The project ID is required to store images in Container Registry.

Enter the following command to view your project ID:

  • Enter the following command to use Cloud Build to build your image:
gcloud builds submit --tag$DEVSHELL_PROJECT_ID/devops-image:v0.1 .

Notice the environment variable in the command. The image will be stored in Container Registry.

  • If asked to enable Cloud Build in your project, type Yes and let it build successfully.

Note: If you receive the error INVALID_ARGUMENT: unable to resolve source wait a few minutes and try again.

In Container Registry, the image name always begins with, followed by the project ID of the project you are working in, followed by the image name and the version.

The period at the end of the command represents the path to the Dockerfile: in this case, it shows the current directory.

  • Return to the Cloud Console and on the Navigation menu, click Container Registry. You must be able to see the built image on the list.
  • Now, navigate to the Cloud Build service, and your build should be listed in the history.
  • You will now try running this image from a GCP Compute Engine virtual machine.
  • Navigate to the Compute Engine service.
  • Click Create Instance to create a new virtual machine.
  • On the Create an instance page, specify the following, and leave the remaining settings as their defaults:
Property  - Value
Container - Deploy a container image to this VM instance
Container image -<your-project-id-here>/devops-image:v0.1 (change the project ID where indicated)
Firewall  - Allow HTTP traffic
  • Click Create.
  • Once the VM starts, create a browser tab and request this new VM’s external IP address. The program should work as before.
  • You will now save your changes to your Git repository.

In Cloud Shell, stage all the local changes, commit them, and push them to the repository as shown:

cd ~/learning-devops/devops-repo
git add --all
git commit -am "Added Docker Support"
git push origin master

Automate builds with Triggers

Here, we will make some changes to the application and then automate the build using the triggers. This helps to update application versions.

  • On the menu, navigate to Container Registry. At this point, you should have a folder named devops-image with at least one container in it.
  • On the Navigation menu, click Cloud Build. The builds history page should open up with at least one or more builds in the history.
  • Click the Triggers link on the left and then click on the Create trigger button.
  • Name the trigger devops-trigger.
  • Select your devops-repo Git repository.
  • Select .*(any branch) for the branch.
  • Choose Dockerfile for Build Configuration and select the default image.

Note: The image below describes the way your build configurations will be.


  • Accept the rest of the defaults, and click Create.
  • To test the trigger, click Run and then Run trigger.
  • Click the History link and you should see a build running.
  • Wait for the build to finish, and then click the link to it to see its details.
  • Scroll down and look at the logs. The output of the build here is what you would have seen if you were running it on your machine.
  • In the Container Registry, you should see a new folder devops-repo with the new image.
  • Return to the Cloud Shell code editor. Find the file in the learning-devops/devops-repo folder.
  • In the main() function, change the title property to This is from build trigger. as shown below:
def main():
    model={"title": "This is from build trigger."}
    return render_template('index.html', model=model)
  • Stage, commit, and push the changes:
cd ~/learning-devops/devops-repo
git add .
git commit -a -m "build trigger test"
git push origin master
  • Return to the Cloud Console and the Cloud Build service. You should see another build running.

Build changes testing

  • When the build completes, click on it to see its details.
  • Under execution details, copy the image link. The format should look something like<your-project-id>/devops-repoxx34345xx.
  • Go to the Compute Engine service. As you did earlier, create a new virtual machine to test this image.
  • Click on the box to deploy a container image to the virtual machine, and paste the copied image.
  • Select Allow HTTP traffic.
  • When the new machine is created, you can test your changes by requesting the virtual machine’s external IP address in your browser. Your new message would be displayed.

Note: You might have to wait for a few minutes after the VM is created for the Docker container to start.


In this tutorial, you built a continuous integration pipeline using the Google Cloud services like Cloud Source Repositories, Cloud Build, Build Triggers, and Container Registry.

You learned how the automation of pipelines works using the build triggers when there is an update in the code repository. You also learned about the basics commands with git and how to spin up the Flask server from the ground up.

You can find the full code here.

Happy coding!

Peer Review Contributions by: Srishilesh P S