@vizir/idempotent-aws-lambda

A fast way to turn your aws lambda function idempotent.

Motivation

This library is design to resolve the idempotent problem of the AWS Lambda.

Some kind of request into AWS lambda should run most than one time, generating inconsistency problems when your function isn't idempotent. You can check more details into aws knowledge center

Installation

$ npm install @vizir/idempotent-aws-lambda

Usage

HTTP

Use the default aws request id to avoid duplicate requests:

module.exports.handler = idempotencyHttpWrapper({
  handler: async (event, context) => {
    // Your lambda functions goes here
    console.log("Processing message", event, context);
    // The return will be cached into provider
    return "OK";
  },
  provider: {
    endpoint: "http://localhost:8000", // used for local development only
    name: "dynamoDB",
    region: "us-east-1",
    tableName: "my-idempotent-table",
  },
  ttl: 5, // ttl in seconds
  id: {
    from: "requestId",
  },
});

Use the request header to extract the idempotency id.

module.exports.handler = idempotencyHttpWrapper({
  handler: async (event, context) => {
    // Your lambda functions goes here
    console.log("Processing message", event, context);
    // The return will be cached into provider
    return "OK";
  },
  provider: {
    endpoint: "http://localhost:8000", // used for local development only
    name: "dynamoDB",
    region: "us-east-1",
    tableName: "my-idempotent-table",
  },
  ttl: 5, // ttl in seconds
  id: {
    from: "header",
    name: "myIdempotencyHeader",
  },
});

Use the request header to extract the idempotency id (with aws request id when header is empty):

module.exports.handler = idempotencyHttpWrapper({
  handler: async (event, context) => {
    // Your lambda functions goes here
    console.log("Processing message", event, context);
    // The return will be cached into provider
    return "OK";
  },
  provider: {
    endpoint: "http://localhost:8000", // used for local development only
    name: "dynamoDB",
    region: "us-east-1",
    tableName: "my-idempotent-table",
  },
  ttl: 5, // ttl in seconds
  id: {
    from: "header",
    name: "myIdempotencyHeader",
    fallback: true,
  },
});

SQS

Prevent duplicate calls into sqs trigger. The ttl cannot be high to avoid retry problems.

The own aws can call your lambda twice, in this case we will ignore and remove from SQS.

There are two ways to handle the idempotency SQS.

One is as follow the example bellow, which means the idempotency key will be the messageId from SQS.

module.exports.sqsHandler = idempotencySQSWrapper({
  handler: async (event, context) => {
    console.log("Processing message", event, context);
    return "OK";
  },
  provider: {
    endpoint: process.env.ENDPOINT,
    name: "dynamoDB",
    region: process.env.REGION,
    tableName: process.env.TABLE_NAME,
  },
  queue: {
    region: process.env.REGION,
    url: process.env.QUEUE_URL,
  },
  ttl: 5,
});

Another way is customizing the idempotency's key, from the payload of the received message.

Let's suppose the message's body is

stream: { eventType: 'SENT', id: '1234567890' }

The idempotency's configuration will be:

module.exports.sqsHandler = idempotencySQSWrapper({
  handler: async (event, context) => {
    console.log("Processing message", event, context);
    return "OK";
  },
  provider: {
    endpoint: process.env.ENDPOINT,
    name: "dynamoDB",
    region: process.env.REGION,
    tableName: process.env.TABLE_NAME,
  },
  queue: {
    region: process.env.REGION,
    url: process.env.QUEUE_URL,
  },
  ttl: 5,
  id: {
    from: "event",
    name: ["stream.id", "stream.eventType"],
  },
});

The result in the table will be a recod, which the key will be: 1234567890SENT.

Support

Tested in Node.js 10-12.

License

The MIT License (MIT)