Introduction

Managing an applicatio’s dependencies and technology stack across cloud and hosted environments is always a challenge. While developing the application, multiple environment-dependent bugs get introduced in the software lifecycle. Containerization can be one of the effective ways to cater to this issue. It is simply a process of packing dependencies and libraries along with the application.

Docker

Docker is a Linux-based, open-source containerized platform used for building, running, and packaging applications using containers. Unlike Virtual Machines (VM), Docker containers are lightweight, requires less memory, and provide OS-level Virtualization. Moreover, these containers are faster and treat easy to manage application components such as microservices.

In this article, we will explore deploying containerized apps on hosted servers and Azure App Services. We will also briefly introduce and work with different container registries like Docker Hub, Azure Container Registry (ACR) to host container images. We will also cover the CI/CD (continuous integration and continuous deployment) process.

CI/CD of the containerized app for hosted servers

We have source code hosted on Azure Repos, a ubuntu 16.04 Linux Server, and Azure DevOps pipelines for CI/CD. For deploying apps on the hosted server, we need to install an Azure pipeline agent on the server.

DevOps Pipelines

Azure DevOps uses build pipelines for continuous integration and, release pipelines are used for continuous deployments.

Build Pipelines

For the build pipeline, go to the pipelines, specify the repository and branch of source code, select build agent to create the pipeline, and add appropriate tasks. We will build and push docker images to a container registry, i.e., Docker Hub or ACR, copy release yml files, and publish artifacts for release pipelines in the building process.

Source Code & Agent

The user must specify the repository and branch where the “Source code” is available. Azure allows multiple platforms for source control, such as Azure Repos, GitHub, Bitbucket, or any other version control platform. In the build pipeline, deployment agents can be changed or edited in “Get Sources” and “Build Pipelines.”

Build Services

It is a Docker Compose task, which will build Docker image services provided in the “docker-compose.yml” while binding with the configuration of “Dockerfile

The user must provide the appropriate configuration according to needs. Here are the basic configurations for this build services task:

Push Services

This Docker Compose task will push the images built in the previous step to the provided container registry, here we are using “Docker Hub”

The user must create a “Service Connection” to provide the appropriate access to the container registry. This will allow the, pipelines to push the images.

Creating Service Connection

To create “Service Connection” go to “project settings, Service Connections, and add “New service connection”..” Then select “Docker Registry” and add the username and password as shown below:

Copy Release File

We will copy “docker-compose.yaml” for release automation via this task.

Copy Release File

The “Publish Artifact” task involves publishing the build artifacts to the release pipeline to deploy the docker containers.

Release Pipelines

Azure DevOps allows continuous deployment using release pipelines. Just like build pipelines, we must specify the deployment agent in release pipelines too. As we will deploy the application on a hosted server, we will use hosted agents installed as a pre-requisite.

We will connect the release pipeline with its appropriate build pipeline using the Publish artifacts, and stages will be used to pull docker images and spin up the appropriate containers at the hosted destination.

Here are the deployment steps of release pipelines, as shown below:

Copy Release File

In this step, we will copy the “docker-compose.yml” from build artifacts to the appropriate path., tThis file will be used to pull and spin up containers based on the configuration.

Deployment

This bash script task will allow Docker to login into the container registry, stop and remove previously deployed containers, pull the docker images from the container registry and spin up the containers based on the “docker-compose.yml” file.

Verify Deployment

This is a simple task just for test the deployment;, one can see the running containers just by using the ps command as

Post-Deployment

In this section, we will briefly overview Docker Hub images, DevOps pipeline logs, and the hosted application in this section.

Docker Images

Docker images will be created and pushed to the “Docker Hub” [3] repository in the build pipelines. On every successful build, the Docker images will be pushed to the registry.

Pipeline Logs

The user can see the pipeline logs by going to the build or release pipelines accordingly. Moreover, to test deployment verification, a separate task has been added. By clicking the logs, verification of deployment can be confirmed.

Hosted Application

In this scenario, we have a “php” based website, which we will deploy as a containerized app on the hosted server. After successful completion of build and release pipelines, it will be deployed successfully.