middy-profiler

Middy middleware for profiling CPU on AWS Lambda. Captured CPU profiling data is put into specified AWS S3 bucket with the following object/file name format:

${functionName}/${awsRequestId}/${fileName}.cpuprofile

By default, file name (${fileName}) is cpu_profile but you can configure it as explained below.

Then, you can download the CPU profiling file from AWS S3 and open with any CPU profiler tool like Chrome DevTools:

• Go to Inspector in Chrome DevTools by browsing to chrome://inspect/:

• Click Open dedicated DevTools for Node to go to the Node.js DevTools page:

• Go to Profiler tab, click the Load button and select the downloaded CPU profiling file to load:

• Then select the Chart to see the CPU profiling as flame graph:

Installation

To install the middleware, you can use NPM:

npm install --save middy-profiler

Note: Requires @middy/core version 2.0.0+

Usage

• Register middy-profiler middleware in your handler:

const middy = require('@middy/core');
const profiler = require('middy-profiler');

const handler = async(event, context) => {
  // Do something meaningful

  return {
    statusCode: 200,
  }
}

module.exports.handler = middy(handler).use(profiler());

• Configure AWS S3 bucket name to put the CPU profiling data by environment variable or options passed to middleware.

  Note 1: Your AWS Lambda function must have enough permission (PutObject) for writing to the specified target AWS S3 bucket.

  Note 2: This configuration is mandatory and if it is not specified, profiling will be disabled.

  • By environment variable: Set MIDDY_PROFILER_S3_BUCKET_NAME environment variable with the target bucket name.

  MIDDY_PROFILER_S3_BUCKET_NAME=my-profiling-bucket

  • By options: Pass the bucket name through options.

  const profiler = require('middy-profiler');
  
  module.exports.handler = 
      middy(handler).
          use(profiler({
              s3: { 
                  bucketName: 'my-profiling-bucket'
              }
          })
      );

• Optionally, if you want to profile since the init phase at coldstart (by default profiler is activated by the start of request which doesn't include initialization phase such as main handler import/require, client/SDK creation, etc ...), you need to activate profiler during bootstrap:

  • By environment variable: Set (or append to existing one) NODE_OPTIONS environment variable with the bootstrap options to initialize profiler at startup.

  NODE_OPTIONS=-r middy-profiler/src/bootstrap

• Optionally, you can configure CPU sampling interval in milliseconds. Please note that a high (for ex. 100, 500, 1000) sampling interval may result in an extremely high level of profiling output (not enough detail) being captured. By default, sampling interval is 10 milliseconds and it can be configured by environment variable or options passed to middleware:

  • By environment variable: Set MIDDY_PROFILER_SAMPLING_INTERVAL environment variable with the desired sampling interval.

  MIDDY_PROFILER_SAMPLING_INTERVAL=50

  • By options: Pass the timeout margin through options.

  const profiler = require('middy-profiler');
  
  module.exports.handler = 
      middy(handler).
          use(profiler({
              samplingInterval: 50
          })
      );

• Optionally, you can configure name of the profiling data file which is put into target AWS S3 bucket. It's value is cpu_profile by default but can be configured by environment variable or options passed to middleware:

  • By environment variable: Set MIDDY_PROFILER_S3_FILE_NAME environment variable with the name of the file.

  MIDDY_PROFILER_S3_FILE_NAME=lambda_invocation_cpu_profile

  • By options: Pass the file bame through options.

  const profiler = require('middy-profiler');
  
  module.exports.handler = 
      middy(handler).
          use(profiler({
              s3: { 
                  fileName: 'lambda_invocation_cpu_profile'
              }
          })
      );

Use Cases

• Vincent Voyer discovered significant performance impact of enabling source maps with the help of this profiler. You can find more info here: https://twitter.com/vvoyer/status/1498436054851981320

Contributing

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

License

Licensed under MIT License.