Post Syndicated from Jessica Veljanovska original https://www.anchor.com.au/blog/2022/10/deploying-containers-to-aws/

Deploying containers to AWS using ECS and CodePipeline 

In this post, it will look at deploying containers to AWS using ECS and CodePipeline. Note that this is only an overview of the process and is not a complete tutorial on how to set this up. 

Containers 101 

However, before we look at how we can deploy Containers onto AWS, it is first worth looking at why we want to use containers, so what are containers?

Containers provide environments for applications to run in isolation. Unlike virtualisation, containers do not require a full guest operating system for each container instance, instead, they share the kernel and other lower-level components of the host operating system as provided by the underlying containerization platform (the most popular of which is Docker, which we will be using in examples from here onwards). This makes containers more efficient at using the underlying hardware resources to run applications. Since Containers are isolated, they can include all their dependencies separate from other running Containers. Suppose that you have two applications that each require specific, conflicting, versions of Python to run, they will not run correctly if this requirement is not met. With containers, you can run both applications with their own environments and dependencies on the same Host Operating system without conflict. 

Containers are also portable, as a developer you can create, run, and test an image on your local workstation and then deploy the same image into your production environment. Of course, deploying into production is never that simple, but that example highlights the flexibility that containers can afford to developers in creating their applications. 

This is achieved by using images, which are read-only templates that provide the containerization platform the instructions required to run the image as a Container. Each image is built from a DockerFile that provides the specification on how to build the image and can also include other images. This can be as simple or as complicated as it needs to be to successfully run the application.

FROM ubuntu:22.04 

COPY . /app 

RUN make /app 

CMD python /app/app.py

However, it is important to know that each image is made up of different layers, which are created based on each line of instruction in the DockerFile that is used to build the image. Each layer is cached by Docker which provides performance benefits to well optimised DockerFiles and the resulting images they create. When the image is run by Docker it creates a Container that flips the layers from the image and adds a runtime Read-Write layer on top, which can be used for logging and any other activity that the application needs to perform and cannot be read from the image. You can use the same image to run as many Containers (running instances of the image) as you desire. Finally, when a Container is removed, the image is retained and only the Read-Write layer is lost. 

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Elastic Container Service 

Elastic Container Service or ECS is AWS’ native Container management system. As an orchestration system it makes it easy to deploy and manage containerized applications at scale with built in scheduling that can allow you to spin up/down Containers at specific times or even configure auto-scaling. ECS has three primary modes of operation, known as launch types. Elastic Container Service or ECS is AWS’ native Container management system. As an orchestration system it makes it easy to deploy and manage containerized applications at scale with built in scheduling that can allow you to spin up/down Containers at specific times or even configure auto-scaling. ECS has three primary modes of operation, known as launch types. The first launch type is the AWS EC2 launch type, where you run the ECS agent on EC2 instances that you maintain and manage. The available resource capacity is dependent on the number and type of EC2 instances that you are using. As you are already billed for the AWS resources consumed (EC2, EBS, etc.), there are no additional charges for using ECS with this launch type. If you are using AWS Outposts, you can use also utilise that capacity instead of Cloud-based EC2 instances. 

The second launch type is the AWS Fargate launch type. This is similar to the EC2 launch type, however, the major difference is that AWS are managing the underlying infrastructure. Because of this there are no inherent capacity constraints, and the billing models is based on the amount of vCPU and memory your Containers consume. 

The last launch type is the External launch type, which is known as ECS Anywhere. This allows you to use the features of ECS with your own on-premises hardware/infrastructure. This is billed at an hourly rate per managed instance. 

ECS operates using a hierarchy that connects together the different aspects of the service and allows flexibility in exactly how the application is run. This hierarchy consists of ECS Clusters, ECS Services, ECS Tasks, and finally the running Containers. We will briefly look at each of these services. ECS Clusters 

ECS Clusters are a logical grouping of ECS Services and their associated ECS Task. A Cluster is where scheduled tasks can be defined, either using fixed intervals or cron expression. If you are using the AWS EC2 Launch Type, it is also where you can configure Auto-Scaling for the EC2 instances in the form of Capacity Providers. 

ECS Services 

ECS Services are responsible for running ECS Tasks. They will ensure that the desired number of Tasks are running and will start new Tasks if an existing Task stops or fails for any reason in order to maintain the desired number of running Tasks. Auto-Scaling can be configured here to automatically update the desired number of Tasks based on CPU and Memory. You can also associate the Service with an Elastic Load Balancer Target Group and if you do this you can also use the number of requests as a metric for Auto-Scaling. 

ECS Tasks 

ECS Tasks are running instances of an ECS Task Definition. The Task Definition describes one or more Containers that make up the Task. This is where the main configuration for the Containers is defined, including the Image/s that are used, the Ports exposed, Environment variables, and if any storage volumes (for example EFS) are required. The Task as a whole can also have Resource sizing configured, which is a hard requirement for Fargate due to its billing model. Task definitions are versioned, so each time you make a change it will create a new revision, allowing you to easily roll back to an older configuration if required.

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Elastic Container Registry 

Elastic Container Registry or ECR, is not formally part of ECS but instead supports it. ECR can be used to publicly or privately store Container images and like all AWS services has granular permissions provided using IAM. The main features of ECR, besides its ability to integrate with ECS, is the built-in vulnerability scanning for images, and the lack of throttling limitations that public container registries might impose. It is not a free service though, so you will need to pay for any usage that falls outside of the included Free-Tier inclusions.

ECR is not strictly required for using ECS, you can continue to use whatever image registry you want. However, if you are using a CodePipeline to deploy your Containers we recommend using ECR purely to avoid throttling issues preventing the CodePipeline from successfully running. 

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CodePipeline 

In software development, a Pipeline is a collection of multiple tools and services working together in order to achieve a common goal, most commonly building and deploying application code. AWS CodePipeline is AWS’ native form of a Pipeline that supports both AWS services as well as external services in order to help automate deployments/releases.

CodePipeline is one part of the complete set of developer tools that AWS provides, which commonly have names starting with “Code”. This is important as by itself CodePipeline can only orchestrate other tooling. For a Pipeline that will deploy a Container to ECS, we will need AWS CodeCommit, AWS CodeBuild, and AWS CodeDeploy. In addition to running the components that are configured, CodePipeline can also provide and retrieve artifacts stored in S3 for each step. For example, it will store the application code from CodeCommit into S3 and provide this to CodeBuild, Code Build will then take this and will create its own artifact files that are provided to CodeDeploy. 

AWS CodeCommit 

AWS CodeCommit is a fully managed source control service that hosts private Git repositories. While this is not strictly required for the CodePipeline, we recommend using it to ensure that AWS has a cached copy of the code at all times. External git repositories can use actions or their own pipelines to push code to CodeCommit when it has been committed. CodeCommit is used in the Source stage of the CodePipeline to both provide the code that is used and to trigger the Pipeline to run when a commit is made. Alternatively, you can use CodeStar Connections to directly use GitHub or BitBucket as the Source stage instead.

AWS CodeBuild 

AWS CodeBuild is a fully managed integration service that can be used to run commands as defined in the BuildSpec that it draws its configuration from, either in CodeBuild itself, or from the Source repository. This flexibility allows it to compile source code, run tests, make API calls, or in our case build Docker Images using the DockerFile that is part of a code repository. CodeBuild is used in the Build stage of the CodePipeline to build the Docker Image, push it to ECR, and update any Environment Variables used later in the deployment.

The following is an example of what a typical BuildSpec might look like for our purposes. 

version: 0.2
  
  
  phases:
  
    pre_build:
  
      commands:
  
        - echo Logging in to Amazon ECR...
  
        - aws --version
  
        - aws ecr get-login-password --region $AWS_DEFAULT_REGION | docker login --username AWS --password-stdin $ACCOUNTID.dkr.ecr.$AWS_DEFAULT_REGION.amazonaws.com
  
    build:
  
      commands:
  
        - echo Build started on `date`
  
        - echo Building the Docker image...
  
        - docker build -t "$REPOSITORY_URI:$IMAGE_TAG-$CODEBUILD_START_TIME" .
  
        - docker tag "$REPOSITORY_URI:$IMAGE_TAG-$CODEBUILD_START_TIME" "$REPOSITORY_URI:$IMAGE_TAG-$CODEBUILD_START_TIME"
  
    post_build:
  
      commands:
  
        - echo Build completed on `date`
  
        - echo Pushing the Docker images...
  
        - docker push "$REPOSITORY_URI:$IMAGE_TAG-$CODEBUILD_START_TIME"
  
        - echo Writing image definitions file...
  
        - printf '{"ImageURI":"%s"}'" $REPOSITORY_URI:$IMAGE_TAG-$CODEBUILD_START_TIME"  > imageDetail.json
  
        - echo $REPOSITORY_URI:$IMAGE_TAG-$CODEBUILD_START_TIME
  
        - sed -i 's|<APP_NAME>|'$IMAGE_REPO_NAME'|g' appspec.yaml taskdef.json
  
        - sed -i 's|<SERVICE_PORT>|'$SERVICE_PORT'|g' appspec.yaml taskdef.json
  
        - sed -i 's|<AWS_ACCOUNT_ID>|'$AWS_ACCOUNT_ID'|g' taskdef.json
  
        - sed -i 's|<MEMORY_RESV>|'$MEMORY_RESV'|g' taskdef.json
  
        - sed -i 's|<IMAGE_NAME>|'$REPOSITORY_URI'\:'$IMAGE_TAG-$CODEBUILD_START_TIME'|g' taskdef.json
  
        - sed -i 's|<IAM_EXEC_ROLE>|'$IAM_EXEC_ROLE'|g' taskdef.json
  
        - sed -i 's|<REGION>|'$REGION'|g' taskdef.json
  
  artifacts:
  
    files:
  
      - appspec.yaml
  
      - taskdef.json
  
      - imageDetail.json

Failures in this step are most likely caused by an incorrect, non-functioning DockerFile or hitting throttling from external Docker repositories. 

AWS CodeDeploy 

AWS CodeDeploy is a fully managed deployment service that integrates with several AWS services including ECS. It can also be used to deploy software to on-premises servers. The configuration of the deployment is defined using an appspec file. CodeDeploy offers several different deployment types and configurations. We tend to use the `Blue/Green` deployment type and the `CodeDeployDefault.ECSAllAtOnce` deployment configuration by default. 

The Blue/Green deployment model allows for the deployment to rollback to the previously deployed Tasks if the deployment is not successful. This makes use of Load Balancer Target Groups to determine if the created Tasks in the ECS Service are healthy. If the health checks fail, then the deployment will fail and trigger a rollback.  

In our ECS CodePipeline, CodeDeploy will run based on the following example appspec.yaml file. Note that the place holder variables in <> are updated with real configuration by the CodeBuild stage.

version: 0.0 

Resources: 

  - TargetService: 

      Type: AWS::ECS::Service 

      Properties: 

        TaskDefinition: <TASK_DEFINITION> 

        LoadBalancerInfo: 

          ContainerName: "<APP_NAME>" 

          ContainerPort: <SERVICE_PORT> 

You may have noticed a lack of configuration regarding the actual Container we will be running up to this point. As we noted earlier, ECS Tasks can use a taskdef file to configure the Task and Containers, which is exactly what we are doing here. One of the files the CodeBuild configuration above expects to be present is taskdef.json. Below is an example taskdef.json file, ss with the appspec.yaml file there are placeholder variables as indicated by <>.

{ 

  "executionRoleArn": "<IAM_EXEC_ROLE>", 

  "containerDefinitions": [ 

    { 

      "name": "<APP_NAME>", 

      "image": "<IMAGE_NAME>", 

      "essential": true, 

      "memoryReservation": <MEMORY_RESV>, 

      "portMappings": [ 

        { 

          "hostPort": 0, 

          "protocol": "tcp", 

          "containerPort": <SERVICE_PORT> 

        } 

      ], 

      "environment": [ 

        { 

          "name": "PORT", 

          "value": "<SERVICE_PORT>" 

        }, 

        { 

          "name": "APP_NAME", 

          "value": "<APP_NAME>" 

        }, 

        { 

          "name": "IMAGE_BUILD_DATE", 

          "value": "<IMAGE_BUILD_DATE>" 

        }, 

      ], 

      "mountPoints": [] 

    } 

  ], 

  "volumes": [], 

  "requiresCompatibilities": [ 

    "EC2" 

  ], 

  "networkMode": "bridge", 

  "family": "<APP_NAME>" 

Failures in this stage of the CodePipeline generally mean that there is something wrong with the Container that is preventing it from starting successfully and passing its health check. Causes of this are varied and rely heavily on having good logging in place. Failures can range from the DockerFile being configured to execute a command that does not exist, to the application itself erroring out when starting for whatever reason might be logged, such as pulling incomplete data from RDS or failing to connect to an external service. 

Summary 

In summary, we have seen what Containers are, why they are useful, and what options AWS provides with its Elastic Container Service (ECS) for running them. Additionally, we looked at what parts of AWS CodePipeline we would need to use in order to deploy our Containers to ECS using CodePipeline.

For further information on the services used, I would highly recommend looking at the documentation that AWS provides. 

• Amazon ECS 
• Amazon ECR 
• AWS CodePipeline 
• AWS CodeCommit 
• AWS CodeBuild 
• AWS CodeDeploy 

For a more hands-on guided walkthrough on setting up ECS and CodePipeline, AWS provide the following resources, there is also plenty of third party material you can find online. 

• Tutorial: Create a pipeline with an Amazon ECR source and ECS-to-CodeDeploy deployment 
• Deploy a Container Web APP on Amazon ECS 
• Amazon ECS Workshop 

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