🛵 What is does

Middy is a very simple middleware engine that allows you to simplify your AWS Lambda code when using Node.js. This middleware aims to simplify the implementations of a idempotent API.

Making an API idempotent is not trivial as much people think, and you could take a look at Lambda Powertools for Python from AWS that does a great job to explain this use case and a concrete way to implement. There's also this great article from Malcolm Featonby, Making retries safe with idempotent APIs featured in the Amazon Builder's Library as Architecture level 300 which falls ins the advanced classification.

🚀 Install

Use your favorite package manager:

yarn add middy-idempotent

npm install middy-idempotent -S

Usage

Besides @middy/core, you must also use @middy/http-json-body-parser since this middleware will read the request body and needed parsed as json. And right now I only tested twith the client provided by the ioredis lib as well, so you'll need to install it too. At tthe bottom there's a write-up where we'll find how to use a Serverless Database service called Upstash for free that is currently (0.0.20) the only storage supported.

handler.use(jsonBodyParser()).use(
  idempotent({
    client: new Redis(process.env.UPSTASH_REDISS),
  })
);

Just place in your code, as soon as possible, passing the Redis client constructor with your rediss:// url. See demo for an example of application with infrastructure provisioned in AWS CD Besides the client, you have th possibility to choose your own idempotency key instead of the whole event:

| Prop | Type | Description | |----------|:--------:|------------| | client | Instance of class Redis | instance of the class Redis provided by the lib ioredis, the only supported at the moment | | body | boolean or string | Optional. If true uses the body sent in the request. If no body is sent, this will yield an error. | | header | string | Optional. If you pass any value, will try to get this value as a key header in your request (i.e, x-forwarded-for and x-idempotency-key) | | path | String. One of "rawPath" or "rawQueryString" | Optional. If you want to target a very specific (and possibly dynamic) path or raw query string in the request | | ttl | number | Optional. Redis keys live forever by default, so being able to set a time to live is useful to avoid running out of memory in your Redis instance, as this will cause your lambdas to fail. Time unit: seconds.

Note that the optional targets are mutually excludents, they obey the hierarchy body > header > path meaning if you pass all of them, it will pick body and if that is not provided header is picked. The default behaviour is use all the event object as idempotency key.

TODO

• [ ] Add more storages (DynamoDB, etc)

📚 Read more

• Redis: Exploring Redis as Serverless Database to solve idempotence in APIs

See Also

🛵 🔐 reCAPTCHA Middleware for Middy: reCAPTCHA validation Middy middleware for yours AWS Lambdas

MIT License

Copyright (c) 2021 Ibrahim Cesar

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