Feature request: allow to set idempotency prefix

[leandrodamascena]

Use case

Original issue: aws-powertools/powertools-lambda-python#5897

The prefix to the Idempotency key is hardcoded to force a fully qualified name based on the location of the function that uses the decorator. There is no simple way of modifying this behavior in order to make that prefix some static value.

https://github.com/aws-powertools/powertools-lambda-typescript/blob/main/packages/idempotency/src/persistence/BasePersistenceLayer.ts#L55

This makes the Idempotency susceptible to future code refactoring. To prevent duplicate handling you can either

Solution/User Experience

A solution is to provide a way to override the key prefix on the makeIdempotent function. An optional argument like keyPrefix that allows a user to provided a fix string. This would allow freedom of refactoring (or even have multiple functions that are controlled by the same idempotency key space).

Considerations:

• This should only control the prefix. The standard behavior of appending # would stay intact

Alternative solutions

Python implementation + documentation: https://github.com/aws-powertools/powertools-lambda-python/pull/5898 

Acknowledgment

• This feature request meets Powertools for AWS Lambda (TypeScript) Tenets
• Should this be considered in other Powertools for AWS Lambda languages? i.e. Python, Java, and .NET

Future readers

Please react with 👍 and your use case to help us understand customer demand.

[dreamorosi]

Thank you for creating the issue Leo.

Note

Below are some more information for the implementation in this side of Powertools for AWS. If anyone is interested in picking this up please leave a comment to claim the issue. A maintainer will assign the issue to you and help you with reviewing your PR. Likewise, if you have any questions before starting, feel free to leave a comment below.

As part of this work we should add a new keyPrefix parameter that customers can use to customize the Idempotency prefix. This is the prefix of the id attribute used to store the Idempotency record in the persistence store.

Normally this prefix is created automatically by the utility using the AWS Lambda function name (aka the name of the resource) and the name of the function in your code being made idempotent (i.e. handler). The logic for how the prefix is constructed is here and an example could be payment-function.handler when making idempotent the handler function within a Lambda function named payment-production

With this change, customers should be able to specify their own prefix. When doing this, the customer-provided prefix will be used instead of the one generated by the utility. Customers should be able to do this when decorating a function, making it idempotent via Middy.js middleware, or higher-order function. Below some examples of how the DX would look like after the change.

const persistenceStore = new DynamoDBPersistenceLayer({
  tableName: 'idempotencyTableName',
});

const processPayment = makeIdempotent(
  async (paymentProps) => {
    // ... process your payload

    return {
      message: 'success',
      statusCode: 200,
    };
  },
  {
    persistenceStore,
    keyPrefix: 'some_custom_value', // <-- new parameter
  }
);

export const handler = async (event) => {
  // ... do something with the event
  return processPayment({
    customerId: event.customerId,
    amount: event.amount
  });
};

// OR


const config = new IdempotencyConfig({});

class MyLambda implements LambdaInterface {
  @idempotent({
    persistenceStore,
    config,
    keyPrefix: 'some_custom_value', // <-- new parameter
   })
  public async handler(_event, _context) {
    // ... process your event
    return {
      message: 'success',
      statusCode: 200,
    };
  }
}

const defaultLambda = new MyLambda();
export const handler = defaultLambda.handler.bind(defaultLambda);

// OR

export const handler = middy(
  async (event) => {
    // ... process your event
).use(
  makeHandlerIdempotent({
    persistenceStore,
    keyPrefix: 'some_custom_value', // <-- new parameter
  })
);

To do this, we should follow this high level plan:

• Add a new optional keyPrefix option to the IdempotencyOptions
• Add the same option to the BasePersistenceLayerOptions type
• Handle the new keyPrefix option in the IdempotencyHandler constructor, and pass it down to the .configure() call here
• Modify the logic here so that the keyPrefix is used whenever present and set to the this.idempotencyKeyPrefix property
• Write unit tests for the new feature, ensuring coverage stays 100%
• Write documentation, you can look at the one in the Python implementation from the PR linked in the OP

Note that there might be other parts of the code to touch that I might have forgotten, make sure to take a closer look at the current implementation before starting.

[shdq]

Hi, I'd like to help with this issue. Could you please assign it to me?