CloudFormation Custom Task Definition POC

custom-task-definition.yml

# Sources:
# https://cloudonaut.io/how-to-create-a-customized-cloudwatch-dashboard-with-cloudformation/
# https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-custom-resources.html
# https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/ECS.html

Resources:
  CustomTaskDefinition:
    Type: 'Custom::TaskDefinition'
    Version: '1.0'
    Properties: 
      ServiceToken: !GetAtt 'CustomResourceFunction.Arn'
      TaskDefinition: |
        {
          containerDefinitions: [
            {
              name: "sleep",
              image: "busybox",
              command: [
                "sleep", 
                "360"
              ],
              mountPoints: [
                {sourceVolume: "efs", containerPath: "/efs"}
              ]
            }
          ], 
          family: "sleep360",
          taskRoleArn: "", // required for EFS permissions
          cpu: "256",
          memory: "512",
          networkMode: "awsvpc",
          volumes: [
            {
              name: "efs",
              efsVolumeConfiguration: {
                fileSystemId: "" // required for EFS
              }
            }
          ]
        }
  CustomResourceFunction:
    Type: 'AWS::Lambda::Function'
    Properties:
      Code:
        ZipFile: |
          const aws = require('aws-sdk')
          const response = require('cfn-response')
          const ecs = new aws.ECS({apiVersion: '2014-11-13'})
          exports.handler = function(event, context) {
            console.log(`AWS SDK Version: ${aws.VERSION}`)
            console.log("REQUEST RECEIVED:\n" + JSON.stringify(event))
            if (event.RequestType === 'Create' || event.RequestType === 'Update') {
              ecs.registerTaskDefinition(eval(`(${event.ResourceProperties.TaskDefinition})`))
                .promise()
                .then(data => {
                  console.log(`Created/Updated task definition ${data.taskDefinition.taskDefinitionArn}`)
                  response.send(event, context, response.SUCCESS, {}, data.taskDefinition.taskDefinitionArn)
                })
                .catch(err => {
                  console.error(err);
                  response.send(event, context, response.FAILED)
                })
            } else if (event.RequestType === 'Delete') {
              ecs.deregisterTaskDefinition({taskDefinition: event.PhysicalResourceId})
                .promise()
                .then(data => {
                  console.log(`Removed task definition ${event.PhysicalResourceId}`)
                  response.send(event, context, response.SUCCESS)
                })
                .catch(err => {
                  if (err.code === 'InvalidParameterException') {
                    console.log(`Task definition: ${event.PhysicalResourceId} does not exist. Skipping deletion.`)
                    response.send(event, context, response.SUCCESS)
                  } else {
                    console.error(err)
                    response.send(event, context, response.FAILED)
                  }
                })
            } else {
              console.error(`Unsupported request type: ${event.RequestType}`)
              response.send(event, context, response.FAILED)
            }
          }
      Handler: 'index.handler'
      MemorySize: 128
      Role: !GetAtt 'CustomResourceRole.Arn'
      Runtime: 'nodejs12.x'
      Timeout: 30
  CustomResourceRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
        - Effect: Allow
          Principal:
            Service: 'lambda.amazonaws.com'
          Action: 'sts:AssumeRole'
      Policies:
      - PolicyName: 'customresource'
        PolicyDocument:
          Statement:
          - Effect: Allow
            Action:
            - 'ecs:DeregisterTaskDefinition'
            - 'ecs:RegisterTaskDefinition'
            Resource: '*'
          - Effect: Allow
            Action:
            - 'logs:CreateLogGroup'
            - 'logs:CreateLogStream'
            - 'logs:PutLogEvents'
            Resource: '*'
          - Effect: Allow
            Action:
            - 'iam:PassRole'
            Resource: '*' # replace with value of taskRoleArn

You are telling it what directory to mount the EFS to inside of the container. Your container pipeline should be running a ‘mkdir -p /var/fuseki/data/admin‘ to create it if it doesn’t already exist.

OK. This is not required with host mounts though -- so the EFS volumes are different in this respect?

OK. This is not required with host mounts though -- so the EFS volumes are different in this respect?

Yes it is required for mounting an EFS volume to a host. You’re telling it what directory to mount the EFS to on the host. Since the idea of this is to not mount to the host, you’re mounting it directly inside of the container.

Doesn't the fs-468514f2.efs.us-east-1.amazonaws.com:/var/fuseki/data/admin syntax refer to EFS host:path? Meaning the missing directory is within EFS?