proposal: add Task Definition Overrides

[iamhopaul123]

Background

As more customers are using Copilot, our current manifest might not meet all their needs. For example in #2101, customers want http.credential to be configurable so as to support private repositories. Also as stated in one of our top issues with the most thumb-ups #948, it would be very helpful if they could overwrite arbitrary fields in their task definitions.

Example Related Issues

• [Manifest] Allow TaskDefinition overrides in the Manifest #948
• Exporting arbitrary variables from all stacks #1919
• Support multiple ports #1783
• Support Private Registries for images #2101

UX Design

For specific fields to override, please refer to https://docs.aws.amazon.com/AmazonECS/latest/APIReference/API_TaskDefinition.html

taskdef_override:
  - path: ContainerDefinitions[0].Ulimits.HardLimit
    value: 1024
  - ContainerDefinitions[0].Ulimits.Name: some limit
  - ContainerDefinitions[0].Ulimits.SoftLimit: 512
  - RequiresCompatibilities: [FARGATE]

Restriction

Users will not be allowed to modify the following fields in the task definition

• Family
• ContainerDefinition.Name (our main container name)

Override Behaviors

• For single-value options like bool, string, or int, the new value replaces the old value.
• For multi-value options like list or map, Copilot concatenates both sets of values.

Milestones

• new override package (subject to future changes), which
  • validate the override rule
  • translates the override rule
  • applies override rules to the unmarshalled CFN template
  • unmarshals and marshals the CFN template correctly
• read the override section in the manifest package
• apply the template override in stack pkg
• add docs and integ tests

[buddhike]

Hey @iamhopaul123, Thanks for the awesome summary of this feature 🙏🏾. Do you know if overrides are going to be available for sidecars as well 😊?

[iamhopaul123]

Hello @BuddySpike sure it will be!