ACI integration Compose features

Compose - Azure Container Instances mapping

This document outlines the conversion of an application defined in a Compose file to ACI objects. At a high-level, each Compose deployment is mapped to a single ACI container group. Each service is mapped to a container in the container group. The Docker ACI integration does not allow scaling of services.

Compose fields mapping

The table below lists supported Compose file fields and their ACI counterparts.

Legend:

• ✓: Implemented
• n: Not yet implemented
• x: Not applicable / no available conversion

Logs

Container logs can be obtained for each container with docker logs <CONTAINER> . The Docker ACI integration does not currently support aggregated logs for containers in a Compose application, see https://github.com/docker/compose-cli/issues/803.

Exposing ports

When one or more services expose ports, the entire ACI container group will be exposed and will get a public IP allocated. As all services are mapped to containers in the same container group, only one service cannot expose a given port number. ACI does not support port mapping, so the source and target ports defined in the Compose file must be the same.

When exposing ports, a service can also specify the service domainname field to set a DNS hostname. domainname will be used to specify the ACI DNS Label Name, and the ACI container group will be reachable at . .azurecontainer.io. All services specifying a `domainname` must set the same value, as it is applied to the entire container group. `domainname` must be unique globally in .azurecontainer.io

Persistent volumes

Docker volumes are mapped to Azure file shares. Only the long Compose volume format is supported meaning that volumes must be defined in the volume section. Volumes are defined with a name, the driver field must be set to azure_file , and driver_options must define the storage account and file share to use for the volume. A service can then reference the volume by its name, and specify the target path to be mounted in the container.

services:
    myservice:
        image: nginx
        volumes:
        - mydata:/mount/testvolumes

volumes:
  mydata:
    driver: azure_file
    driver_opts:
      share_name: myfileshare
      storage_account_name: mystorageaccount

The short volume syntax is not allowed for ACI volumes, as it was designed for local path bind mounting when running local containers. A Compose file can define several volumes, with different Azure file shares or storage accounts.

Credentials for storage accounts will be automatically fetched at deployment time using the Azure login to retrieve the storage account key for each storage account used.

Secrets

Secrets can be defined in compose files, and will need secret files available at deploy time next to the compose file. The content of the secret file will be made available inside selected containers, by default under /run/secrets/<SECRET_NAME> . External secrets are not supported with the ACI integration.

services:
    nginx:
        image: nginx
        secrets:
          - mysecret1
    db:
        image: mysql
        secrets:
          - mysecret2

secrets:
  mysecret1:
    file: ./my_secret1.txt
  mysecret2:
    file: ./my_secret2.txt

The nginx container will have secret1 mounted as /run/secrets/mysecret1 , the db container will have secret2 mounted as /run/secrets/mysecret2

A target can also be specified to set the name of the mounted file or by specifying an absolute path where to mount the secret file

services:
    nginx:
        image: nginx
        secrets:
          - source: mysecret1
            target: renamedsecret1.txt
    db:
        image: mysql
        secrets:
          - source: mysecret1
            target: /mnt/dbmount/mysecretonmount1.txt
          - source: mysecret2
            target: /mnt/dbmount/mysecretonmount2.txt

secrets:
  mysecret1:
    file: ./my_secret1.txt
  mysecret2:
    file: ./my_secret2.txt

In this example the nginx service will have its secret mounted to /run/secrets/renamedsecret1.txt and db will have 2 files ( mysecretonmount1.txt and mysecretonmount2.txt ). Both of them with be mounted in the same folder ( /mnt/dbmount/ ).

Note: Relative file paths are not allowed in the target

Note: Secret files cannot be mounted in a folder next to other existing files

Container Resources

CPU and memory reservations and limits can be set in compose. Resource limits must be greater than reservation. In ACI, setting resource limits different from resource reservation will cause containers in the same container group to compete for resources. Resource limits cannot be greater than the total resource reservation for the container group. (Therefore single containers cannot have resource limits different from resource reservations)

services:
  db:
    image: mysql
    deploy:
      resources:
        reservations:
          cpus: '2'
          memory: 2G
        limits:
          cpus: '3'
          memory: 3G
  web:
    image: nginx
    deploy:
      resources:
        reservations:
          cpus: '1.5'
          memory: 1.5G

In this example, the db container will be allocated 2 CPUs and 2G of memory. It will be allowed to use up to 3 CPUs and 3G of memory, using some of the resources allocated to the web container. The web container will have its limits set to the same values as reservations, by default.

Healthchecks

A health check can be described in the healthcheck section of each service. This is translated to a LivenessProbe in ACI. If the health check fails then the container is considered unhealthy and terminated. In order for the container to be restarted automatically, the service needs to have a restart policy other than none to be set. Note that the default restart policy if one isn’t set is any .

services:
  web:
    image: nginx
    deploy:
      restart_policy:
        condition: on-failure
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:80"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 40s

Note: that the test command can be a string or an array starting or not by NONE , CMD , CMD-SHELL . In the ACI implementation, these prefixes are ignored.

ACI integration container features

Azure Container Instances: running single containers

Single containers can be executed on ACI with the docker run command. A single container is executed in its own ACI container group, which will contain a single container.

Containers can be listed with the docker ps command, and stopped and removed with docker stop <CONTAINER> and docker rm <CONTAINER> .

Docker run options for ACI containers

The table below lists supported docker run flags and their ACI counterparts.

Legend:

• ✓: Implemented
• n: Not yet implemented
• x: Not applicable / no available conversion

Exposing ports

You can expose one or more ports of a container with docker run -p <PORT>:<PORT> If ports are exposed when running a container, the corresponding ACI container group will be exposed with a public IP allocated and the required port(s) accessible.

Note: ACI does not support port mapping, so the same port number must be specified when using -p <PORT>:<PORT> .

When exposing ports, a container can also specify the service --domainname flag to set a DNS hostname. domainname will be used to specify the ACI DNS Label Name, and the ACI container group will be reachable at <DOMAINNANE>.<REGION>.azurecontainer.io . domainname must be unique globally in .azurecontainer.io

Persistent volumes

Docker volumes are mapped to Azure File shares, each file share is part of an Azure Storage Account. One or more volumes can be specified with docker run -v <STORAGE-ACCOUNT>/<FILESHARE>:<TARGET-PATH> .

A run command can use the --volume or -v flag several times for different volumes. The volumes can use the same or different storage accounts. The target paths for different volume mounts must be different and not overlap. There is no support for mounting a single file, or mounting a subfolder from an Azure File Share.

Credentials for storage accounts will be automatically fetched at deployment time using the Azure login to retrieve the storage account key for each storage account used.

Container Resources

CPU and memory reservations can be set when running containers with docker run --cpus 1.5 --memory 2G .

It is not possible to set resource limits that differ from resource reservation on single containers. ACI allows setting resource limits for containers in a container group but these limits must stay within the reserved resources for the entire group. In the case of a single container deployed in a container group, the resource limits must be equal to the resource reservation.

Logs

You can view container logs with the command docker logs <CONTAINER-ID> .

You can follow logs with the --follow ( -f ) option. When running a container with docker run , by default the command line stays attached to container logs when the container starts. Use docker run --detach to not follow logs once the container starts.

Note: Following ACI logs may have display issues especially when resizing a terminal that is following container logs. This is due to ACI providing raw log pulling but no streaming of logs. Logs are effectively pulled every 2 seconds when following logs.

Healthchecks

A health check can be described using the flags prefixed by --health- . This is translated into LivenessProbe for ACI. If the health check fails then the container is considered unhealthy and terminated. In order for the container to be restarted automatically, the container needs to be run with a restart policy (set by the --restart flag) other than no . Note that the default restart policy if one isn’t set is no .

In order to restart automatically, the container also need to have a restart policy set with --restart ( docker run defaults to no restart policy)

Deploying Docker containers on Azure

Overview

The Docker Azure Integration enables developers to use native Docker commands to run applications in Azure Container Instances (ACI) when building cloud-native applications. The new experience provides a tight integration between Docker Desktop and Microsoft Azure allowing developers to quickly run applications using the Docker CLI or VS Code extension, to switch seamlessly from local development to cloud deployment.

In addition, the integration between Docker and Microsoft developer technologies allow developers to use the Docker CLI to:

• Easily log into Azure
• Set up an ACI context in one Docker command allowing you to switch from a local context to a cloud context and run applications quickly and easily
• Simplify single container and multi-container application development using the Compose specification, allowing a developer to invoke fully Docker-compatible commands seamlessly for the first time natively within a cloud container service

Also see the full list of container features supported by ACI and full list of compose features supported by ACI.

Prerequisites

To deploy Docker containers on Azure, you must meet the following requirements:

1. Download and install the latest version of Docker Desktop.

   • Download for Mac
   • Download for Windows

   Alternatively, install the Docker Compose CLI for Linux.

2. Ensure you have an Azure subscription. You can get started with an Azure free account.

Run Docker containers on ACI

Docker not only runs containers locally, but also enables developers to seamlessly deploy Docker containers on ACI using docker run or deploy multi-container applications defined in a Compose file using the docker compose up command.

The following sections contain instructions on how to deploy your Docker containers on ACI. Also see the full list of container features supported by ACI.

Log into Azure

Run the following commands to log into Azure:

$ docker login azure

This opens your web browser and prompts you to enter your Azure login credentials. If the Docker CLI cannot open a browser, it will fall back to the Azure device code flow and lets you connect manually. Note that the Azure command line login is separated from the Docker CLI Azure login.

Alternatively, you can log in without interaction (typically in scripts or continuous integration scenarios), using an Azure Service Principal, with docker login azure --client-id xx --client-secret yy --tenant-id zz

Note

Logging in through the Azure Service Provider obtains an access token valid for a short period (typically 1h), but it does not allow you to automatically and transparently refresh this token. You must manually re-login when the access token has expired when logging in with a Service Provider.

You can also use the --tenant-id option alone to specify a tenant, if you have several ones available in Azure.

Create an ACI context

After you have logged in, you need to create a Docker context associated with ACI to deploy containers in ACI. Creating an ACI context requires an Azure subscription, a resource group, and a region. For example, let us create a new context called myacicontext :

$ docker context create aci myacicontext

This command automatically uses your Azure login credentials to identify your subscription IDs and resource groups. You can then interactively select the subscription and group that you would like to use. If you prefer, you can specify these options in the CLI using the following flags: --subscription-id , --resource-group , and --location .

If you don’t have any existing resource groups in your Azure account, the docker context create aci myacicontext command creates one for you. You don’t have to specify any additional options to do this.

After you have created an ACI context, you can list your Docker contexts by running the docker context ls command:

NAME                TYPE                DESCRIPTION                               DOCKER ENDPOINT                KUBERNETES ENDPOINT   ORCHESTRATOR
myacicontext        aci                 myResourceGroupGTA@eastus
default *           moby              Current DOCKER_HOST based configuration   unix:///var/run/docker.sock                          swarm

Run a container

Now that you’ve logged in and created an ACI context, you can start using Docker commands to deploy containers on ACI.

There are two ways to use your new ACI context. You can use the --context flag with the Docker command to specify that you would like to run the command using your newly created ACI context.

$ docker --context myacicontext run -p 80:80 nginx

Or, you can change context using docker context use to select the ACI context to be your focus for running Docker commands. For example, we can use the docker context use command to deploy an Nginx container:

$ docker context use myacicontext
$ docker run -p 80:80 nginx

After you’ve switched to the myacicontext context, you can use docker ps to list your containers running on ACI.

In the case of the demonstration Nginx container started above, the result of the ps command will display in column “PORTS” the IP address and port on which the container is running. For example, it may show 52.154.202.35:80->80/tcp , and you can view the Nginx welcome page by browsing http://52.154.202.35 .

To view logs from your container, run:

$ docker logs <CONTAINER_ID>

To execute a command in a running container, run:

$ docker exec -t <CONTAINER_ID> COMMAND

To stop and remove a container from ACI, run:

$ docker stop <CONTAINER_ID>
$ docker rm <CONTAINER_ID>

You can remove containers using docker rm . To remove a running container, you must use the --force flag, or stop the container using docker stop before removing it.

Note

The semantics of restarting a container on ACI are different to those when using a local Docker context for local development. On ACI, the container will be reset to its initial state and started on a new node. This includes the container’s filesystem so all state that is not stored in a volume will be lost on restart.

Running Compose applications

You can also deploy and manage multi-container applications defined in Compose files to ACI using the docker compose command. All containers in the same Compose application are started in the same container group. Service discovery between the containers works using the service name specified in the Compose file. Name resolution between containers is achieved by writing service names in the /etc/hosts file that is shared automatically by all containers in the container group.

Also see the full list of compose features supported by ACI.

1. Ensure you are using your ACI context. You can do this either by specifying the --context myacicontext flag or by setting the default context using the command docker context use myacicontext .

2. Run docker compose up and docker compose down to start and then stop a full Compose application.

By default, docker compose up uses the docker-compose.yaml file in the current folder. You can specify the working directory using the --workdir flag or specify the Compose file directly using docker compose --file mycomposefile.yaml up .

You can also specify a name for the Compose application using the --project-name flag during deployment. If no name is specified, a name will be derived from the working directory.

Containers started as part of Compose applications will be displayed along with single containers when using docker ps . Their container ID will be of the format: <COMPOSE-PROJECT>_<SERVICE> . These containers cannot be stopped, started, or removed independently since they are all part of the same ACI container group. You can view each container’s logs with docker logs . You can list deployed Compose applications with docker compose ls . This will list only compose applications, not single containers started with docker run . You can remove a Compose application with docker compose down .

Note

The current Docker Azure integration does not allow fetching a combined log stream from all the containers that make up the Compose application.

Updating applications

From a deployed Compose application, you can update the application by re-deploying it with the same project name: docker compose --project-name PROJECT up .

Updating an application means the ACI node will be reused, and the application will keep the same IP address that was previously allocated to expose ports, if any. ACI has some limitations on what can be updated in an existing application (you will not be able to change CPU/memory reservation for example), in these cases, you need to deploy a new application from scratch.

Updating is the default behavior if you invoke docker compose up on an already deployed Compose file, as the Compose project name is derived from the directory where the Compose file is located by default. You need to explicitly execute docker compose down before running docker compose up again in order to totally reset a Compose application.

Releasing resources

Single containers and Compose applications can be removed from ACI with the docker prune command. The docker prune command removes deployments that are not currently running. To remove running depoyments, you can specify --force . The --dry-run option lists deployments that are planned for removal, but it doesn’t actually remove them.

$ ./bin/docker --context acicontext prune --dry-run --force
Resources that would be deleted:
my-application
Total CPUs reclaimed: 2.01, total memory reclaimed: 2.30 GB

Exposing ports

Single containers and Compose applications can optionally expose ports. For single containers, this is done using the --publish ( -p ) flag of the docker run command : docker run -p 80:80 nginx .

For Compose applications, you must specify exposed ports in the Compose file service definition:

services:
  nginx:
    image: nginx
    ports:
      - "80:80"

Note

ACI does not allow port mapping (that is, changing port number while exposing port). Therefore, the source and target ports must be the same when deploying to ACI.

All containers in the same Compose application are deployed in the same ACI container group. Different containers in the same Compose application cannot expose the same port when deployed to ACI.

By default, when exposing ports for your application, a random public IP address is associated with the container group supporting the deployed application (single container or Compose application). This IP address can be obtained when listing containers with docker ps or using docker inspect .

DNS label name

In addition to exposing ports on a random IP address, you can specify a DNS label name to expose your application on an FQDN of the form: <NAME>.region.azurecontainer.io .

You can set this name with the --domainname flag when performing a docker run , or by using the domainname field in the Compose file when performing a docker compose up :

services:
  nginx:
    image: nginx
    domainname: "myapp"
    ports:
      - "80:80"

Note

The domain of a Compose application can only be set once, if you specify the domainname for several services, the value must be identical.

The FQDN <DOMAINNAME>.region.azurecontainer.io must be available.

Using Azure file share as volumes in ACI containers

You can deploy containers or Compose applications that use persistent data stored in volumes. Azure File Share can be used to support volumes for ACI containers.

Using an existing Azure File Share with storage account name mystorageaccount and file share name myfileshare , you can specify a volume in your deployment run command as follows:

$ docker run -v mystorageaccount/myfileshare:/target/path myimage

The runtime container will see the file share content in /target/path .

In a Compose application, the volume specification must use the following syntax in the Compose file:

myservice:
  image: nginx
  volumes:
    - mydata:/mount/testvolumes

volumes:
  mydata:
    driver: azure_file
    driver_opts:
      share_name: myfileshare
      storage_account_name: mystorageaccount

Note

The volume short syntax in Compose files cannot be used as it is aimed at volume definition for local bind mounts. Using the volume driver and driver option syntax in Compose files makes the volume definition a lot more clear.

In single or multi-container deployments, the Docker CLI will use your Azure login to fetch the key to the storage account, and provide this key with the container deployment information, so that the container can access the volume. Volumes can be used from any file share in any storage account you have access to with your Azure login. You can specify rw (read/write) or ro (read only) when mounting the volume ( rw is the default).

Managing Azure volumes

To create a volume that you can use in containers or Compose applications when using your ACI Docker context, you can use the docker volume create command, and specify an Azure storage account name and the file share name:

$ docker --context aci volume create test-volume --storage-account mystorageaccount
[+] Running 2/2
 â ¿ mystorageaccount  Created                         26.2s
 â ¿ test-volume       Created                          0.9s
mystorageaccount/test-volume

By default, if the storage account does not already exist, this command creates a new storage account using the Standard LRS as a default SKU, and the resource group and location associated with your Docker ACI context.

If you specify an existing storage account, the command creates a new file share in the existing account:

$ docker --context aci volume create test-volume2 --storage-account mystorageaccount
[+] Running 2/2
 â ¿ mystorageaccount   Use existing                    0.7s
 â ¿ test-volume2       Created                         0.7s
mystorageaccount/test-volume2

Alternatively, you can create an Azure storage account or a file share using the Azure portal, or the az command line.

You can also list volumes that are available for use in containers or Compose applications:

$ docker --context aci volume ls
ID                                 DESCRIPTION
mystorageaccount/test-volume       Fileshare test-volume in mystorageaccount storage account
mystorageaccount/test-volume2      Fileshare test-volume2 in mystorageaccount storage account

To delete a volume and the corresponding Azure file share, use the volume rm command:

$ docker --context aci volume rm mystorageaccount/test-volume
mystorageaccount/test-volume

This permanently deletes the Azure file share and all its data.

When deleting a volume in Azure, the command checks whether the specified file share is the only file share available in the storage account. If the storage account is created with the docker volume create command, docker volume rm also deletes the storage account when it does not have any file shares. If you are using a storage account created without the docker volume create command (through Azure portal or with the az command line for example), docker volume rm does not delete the storage account, even when it has zero remaining file shares.

Environment variables

When using docker run , you can pass the environment variables to ACI containers using the --env flag. For Compose applications, you can specify the environment variables in the Compose file with the environment or env-file service field, or with the --environment command line flag.

Health checks

You can specify a container health checks using either the --healthcheck- prefixed flags with docker run , or in a Compose file with the healthcheck section of the service.

Health checks are converted to ACI LivenessProbe s. ACI runs the health check command periodically, and if it fails, the container will be terminated.

Health checks must be used in addition to restart policies to ensure the container is then restarted on termination. The default restart policy for docker run is no which will not restart the container. The default restart policy for Compose is any which will always try restarting the service containers.

Example using docker run :

$ docker --context acicontext run -p 80:80 --restart always --health-cmd "curl http://localhost:80" --health-interval 3s  nginx

Example using Compose files:

services:
  web:
    image: nginx
    deploy:
      restart_policy:
        condition: on-failure
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:80"]
      interval: 10s

Private Docker Hub images and using the Azure Container Registry

You can deploy private images to ACI that are hosted by any container registry. You need to log into the relevant registry using docker login before running docker run or docker compose up . The Docker CLI will fetch your registry login for the deployed images and send the credentials along with the image deployment information to ACI. In the case of the Azure Container Registry, the command line will try to automatically log you into ACR from your Azure login. You don’t need to manually login to the ACR registry first, if your Azure login has access to the ACR.

Using ACI resource groups as namespaces

You can create several Docker contexts associated with ACI. Each context must be associated with a unique Azure resource group. This allows you to use Docker contexts as namespaces. You can switch between namespaces using docker context use <CONTEXT> .

When you run the docker ps command, it only lists containers in your current Docker context. There won’t be any contention in container names or Compose application names between two Docker contexts.

Install the Docker Compose CLI on Linux

The Docker Compose CLI adds support for running and managing containers on Azure Container Instances (ACI).

Install Prerequisites

• Docker 19.03 or later

Install script

You can install the new CLI using the install script:

$ curl -L https://raw.githubusercontent.com/docker/compose-cli/main/scripts/install/install_linux.sh | sh

Manual install

You can download the Docker ACI Integration CLI from the latest release page.

You will then need to make it executable:

$ chmod +x docker-aci

To enable using the local Docker Engine and to use existing Docker contexts, you must have the existing Docker CLI as com.docker.cli somewhere in your PATH . You can do this by creating a symbolic link from the existing Docker CLI:

$ ln -s /path/to/existing/docker /directory/in/PATH/com.docker.cli

Note

The PATH environment variable is a colon-separated list of directories with priority from left to right. You can view it using echo $PATH . You can find the path to the existing Docker CLI using which docker . You may need root permissions to make this link.

On a fresh install of Ubuntu 20.04 with Docker Engine already installed:

$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
$ which docker
/usr/bin/docker
$ sudo ln -s /usr/bin/docker /usr/local/bin/com.docker.cli

You can verify that this is working by checking that the new CLI works with the default context:

$ ./docker-aci --context default ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
$ echo $?
0

To make this CLI with ACI integration your default Docker CLI, you must move it to a directory in your PATH with higher priority than the existing Docker CLI.

Again, on a fresh Ubuntu 20.04:

$ which docker
/usr/bin/docker
$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
$ sudo mv docker-aci /usr/local/bin/docker
$ which docker
/usr/local/bin/docker
$ docker version
...
 Azure integration  0.1.4
...

Supported commands

After you have installed the Docker ACI Integration CLI, run --help to see the current list of commands.

Uninstall

To remove the Docker Azure Integration CLI, you need to remove the binary you downloaded and com.docker.cli from your PATH . If you installed using the script, this can be done as follows:

$ sudo rm /usr/local/bin/docker /usr/local/bin/com.docker.cli

Feedback

Thank you for trying out Docker Azure Integration. Your feedback is very important to us. Let us know your feedback by creating an issue in the compose-cli GitHub repository.