Docker Containers and Azure – An Introduction

The Problem

I wanted to start using Docker Containers on Azure as I had been using them locally for ages and found them very useful. I had progressed to using Docker Compose for multi-container apps and even for single-container apps as the compose-file contained all the information needed to run the container rather than remember port-mappings, volumes etc for the docker run command.

However….the documentation for containers on Azure is confusing. It’s simple to get a container up and running but it’s not so simple to understand what/where/why. Hence this article

The problem is compounded by there being many ways to do the same thing (a common MS theme) so it is possible to run Docker containers from the Docker CLI, they can also be run from the Azure CLI (an installable add-in) and can also be configured and run from the Azure Portal web-interface.

In addition, there are “different” ways to run Docker containers within Azure itself, they can be run as part of “App Services” as a Web-Application (see below) or can be run as an Azure Container Instance (ACI).

And…to complicate matters, Docker Compose from the Docker CLI was supported although that support was removed in December 2023. And (2)……Docker Compose multiple containers are tricky to run in any event as “App Services Web Applications” do not support port-mapping and only expose ports 80 and 443, so, if you have, say, a web front-end and webapi in the same Compose file using ports 8080 and 8082 you are stuffed.

Confused. Well I was and hopefully this article will make you less so

TLDR;

In case you don’t want to read the below

Watch An Introduction to Containers in Azure
Read Deploying containers from the Docker CLI, it does what it says on the tin
Read Deploying containers from the Azure CLI. It does what it says on the tin
Read Deploying Multi-conainers using Docker Compose and this Tutorial. They does what it says on the tin. Unfortunately, Docker no longer supports Compose with Azure
Read Container Groups in Azure and Deployinga multi-container group using a YAML File for an alternative to Docker Compose. NB I haven’t worked out how to do this yet

Useful information

Docker Compose from Docker CLI no longer supported
“Web Apps” do not support port-mapping. They only expose ports 80 and 443 – this makes multi-container apps exposing enpoints almost impossible in one Compose file.
Azure Container Instances support port mapping

ToDo (for me, then I’ll update this article)

YAML multi-container deployment and port mapping(s).
Kubernetes deployment
Where there is a supported way to deploy Docker Compose with multiple endpoints

Docker CLI

Docker Context

First read Deploying containers from the Docker CLI

Using Azure from the Docker CLI requires a “Docker Context” be set up which contains all the details for Azure. The context can be “used” and the the user can return to the local “default” context

docker context list

NAME TYPE DESCRIPTION DOCKER ENDPOINT KUBERNETES ENDPOINT ORCHESTRATOR
default moby Current DOCKER_HOST based configuration npipe:////./pipe/docker_engine
desktop-linux moby Docker Desktop npipe:////./pipe/dockerDesktopLinuxEngine
myacicontext * aci myresourcegroup

# Use Azure 
docker context use myacicontext


docker run -p 80:80 mcr.microsoft.com/azuredocs/aci-helloworld

# Use local docker
docker context use default

Single Containers

First read Deploying containers from the Docker CLI

docker context use myacicontext
docker run -p 80:80 mcr.microsoft.com/azuredocs/aci-helloworld

This runs the container as an Azure Container Instance (ACI). Port remapping cannot be done but port-numbers can be exposed.

Compose Files

First Read Deploying Multi-conainers using Docker Compose and this Tutorial

docker context use myacicontext 
docker compose up

This creates and Azure App Services WebApp. Port remapping cannot be done. The Webapp exposes only ports 80 and 443 (I believed mapped internally to 80 and 443). A compose file cotnaining multiple containers exposing multiple endpoints will be tricky to get working (i.e. it won’t work I think)

Azure CLI

Running a Container

FirstRead Deploying containers from the Azure CLI

Create an Azure Resource Group

az group create --name myResourceGroup --location uksouth

Run the container

az container create --resource-group myResourceGroup 
    --name mycontainer 
    --image mcr.microsoft.com/azuredocs/aci-helloworld 
    --dns-name-label aci-demo 
    --ports 8000

This creates an Azure Container Instance (ACI) and exposes port 8000 (port remapping is not supported).

Compose FIle

First read Deploying Multi-conainers using Docker Compose and this Tutorial.

Create an Azure Resource Group

az group create --name myResourceGroup --location uksouth

Create an App Service Plan (this examples uses linux). The “sku” I think can be set to F1 (i.e. free service)

az appservice plan create --name myAppServicePlan --resource-group myResourceGroup --sku S1 --is-linux

Create webapp with the compose file as the “source” (example taken from MS uses WordPress)

az webapp create --resource-group myResourceGroup --plan myAppServicePlan --name <app-name> --multicontainer-config-type compose --multicontainer-config-file docker-compose-wordpress.yml

This creates an Azure App Services WebApp. Port remapping is not supported. Only ports 80 and 443 are exposed.

Azure Portal Interface

TBA

Summary

Method	Command	Creates	Notes
Docker cli	docker run	ACI	No port mapping, multiple ports can be exposed
Docker cli docker compose	docker compose up	Azure WebApp	No port mapping, only ports 80,443 exposed
Azure cli (container)	az container create	ACI	No port mapping, multiple ports can be exposed
Azure cli (compose)	az webapp create	WebApp	No port mapping, only ports 80,443 exposed

Docker CLI and Compose Information Message

From the Docker CLI when using a Docker Context for Azure and you do

docker compose up

You get the following message

Docker Compose's integration for ECS and ACI will be retired in November 2023. Learn more: https://docs.docker.com/go/compose-ecs-eol/

What that means, I think, is that Docker have stopped supported Compose from the Docker CLI. I’m not sure if you can use/is-supported Docker Compose from the azure CLI

DRNJ