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    2.5.7 • Public • Published

    Middy warmup middleware

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    Warmup middleware for the middy framework, the stylish Node.js middleware engine for AWS Lambda

    Warmup middleware that helps to reduce the cold-start issue. Compatible by default with serverless-plugin-warmup, but it can be configured to suit your implementation.

    This middleware allows you to specify a schedule to keep Lambdas that always need to be very responsive warmed-up. It does this by regularly invoking the Lambda, but will terminate early to avoid the actual handler logic from being run.

    If you use serverless-plugin-warmup the scheduling part is done by the plugin and you just have to attach the middleware to your "middyfied" handler. If you don't want to use the plugin you have to create the schedule yourself and define the isWarmingUp function to define whether the current event is a warmup event or an actual business logic execution.

    Important: AWS recently announced Lambda Provisioned Concurrency. If you have this enabled, you do not need this middleware.

    To update your code to use Provisioned Concurrency see:


    To install this middleware you can use NPM:

    npm install --save @middy/warmup


    • isWarmingUp: a function that accepts the event object as a parameter and returns true if the current event is a warmup event and false if it's a regular execution. The default function will check if the event object has a source property set to serverless-plugin-warmup.

    Sample usage

    const middy = require('@middy/core')
    const warmup = require('@middy/warmup')
    const isWarmingUp = (event) => event.isWarmingUp === true
    const originalHandler = (event, context, cb) => {
      /* ... */
    const handler = middy(originalHandler)
      .use(warmup({ isWarmingUp }))

    Middy documentation and examples

    For more documentation and examples, refers to the main Middy monorepo on GitHub or Middy official website.


    Everyone is very welcome to contribute to this repository. Feel free to raise issues or to submit Pull Requests.


    Licensed under MIT License. Copyright (c) 2017-2021 Luciano Mammino, will Farrell, and the Middy team.

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    npm i @middy/warmup

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    • lmammino
    • middyjs
    • willfarrell