fargate-helper

How It Works

This tool creates or updates a Fargate service, along with the pieces that it relies on (ELB Rules, Target Group, Health Check, etc.).

It assumes that an image has been pushed to Docker Hub - it takes the image name and creates a Fargate service around it.

The tool supports the following actions:

• create: Creates a service
• delete: Deletes a service
• service: Creates or updates a service (depending on if it already exists)
• update: Updates a service

The syntax for the script is:
fargate <action> <options>

Example (creates or updates the service my-service with the specified parameters):

fargate service \
  --command "node lib/service.js" \
  --containerPort 3000 \
  --cpu 1024 \
  --env key=value \
  --image bespoken/my-service-image \
  --memory 2048 \
  --name my-service

For create, the script will:

1. Register a task definition
2. Create an ELB target group, with health check
3. Create an ELB rule for the target group - assigned to <SERVICE_NAME>.bespoken.io
4. Create a service

For update, the script will:

1. Register a task definition
2. Update the service

For delete, the script will:

1. Delete ELB rule associated with the service
2. Delete the target group associated with the service
3. Update the desiredCount to 0 for the service (necessary before deletion)
4. Delete the service

Setup

Install the package:
npm install fargate-helper -g

Set these environment variables - for the AWS SDK that this relies on:

• AWS_ACCESS_KEY_ID
• AWS_SECRET_ACCESS_KEY
• AWS_DEFAULT_REGION - defaults to us-east-1 if not set

Deployment Configuration

The values for configuring the service will come from three places:

1. Command-line
2. Environment variables
3. AWS Secrets - the "fargate-helper" key

Command-Line Configuration

For the command-line, values are passed in with the format:
--name value

For values with spaces, they should be passed in as so:
--name "my value"

NOTE The memory and CPU must be valid for Fargate. The supported configurations are here:
https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-cpu-memory-error.html

Environment Variables

Values can also be set via environment variable

AWS Secret Configuration

We store certain key default values, such as DockerHub credentials, in defaults in our AWS Secrets.

They can be found under the name "fargate-helper". Values we store there are:

• accountId: The AWS account ID
• albArn: The ARN for the ALB being used for this account
• cluster: The fargate cluster name
• dockerHubSecretArn: The name of the AWS Secret that stores our docker credentials
• listenerArn: The ARN for the ALB listener being used for this account
• roleArn: Used for taskRoleArn and executionRoleArn
• securityGroup: The VPC security group to use
• subnets: The list of subnets to use
• vpcId: The VPC ID used by this configuration - specified when creating the target group on the ALB

The AWS secret values are meant to be one universal defaults for the account

Required Values

These values must be manually configured for the deployment to run:

• command: The command to run for the Docker service
• containerPort: The port the service should run on
• cpu: The CPU allocated for the service, where 1024 is equal to a full CPU
• image: The DockerHub image to use for this service
• memory: The amount of memory allocated for the service
• name: The name of the service

Other Important Values

Though not required, these are useful parameters for more advanced cases:

• logGroup: The CloudWatch Log Group to use - defaults to fargate-cluster
• passEnv: "true" or "false" - defaults to true. If set to false, will not automatically set pass thru environment variables in the build environment to the container environment
• taskDefinition: A file to use as the baseline for the taskDefinition - if not specified, just uses the default that is included in the code

Container Configuration

Environment variables can also be set inside the running container.

If --passEnv is set to true, we take all the environment variables currently set and pass them to the container in the taskDefinition, under environment.

Environment variables in the container can also be set by specifying on the command-line:
fargate --env KEY=VALUE

This will set the environment variable key to value inside the container.

ELB Configuration

By default, we create a target group with rules on our ELB when first creating the service.

The target group will be configured:

• With a health-check that pings the service every thirty seconds, via a GET on /
• With a rule that directs traffic for <SERVICE_NAME>.bespoken.io to the service

For more complex ELB configurations, we recommend they be done manually, and then only update be called (which does not modify the ELB configuration).

Example

To see a sample project that uses this, check out the Utterance Tester:
https://github.com/bespoken/UtteranceTester

In particular, here is the Circle CI configuration:
https://github.com/bespoken/UtteranceTester/blob/master/.circleci/config.yml#L32