example-function.Tracer.Middleware.ts

import middy from '@middy/core';
import { Context } from 'aws-lambda';
import { Events } from '@aws-lambda-powertools/commons';
import { captureLambdaHandler, Tracer } from '@aws-lambda-powertools/tracer';

const tracer = new Tracer({ serviceName: 'tracerMiddlewareFn' });
// Alternatively, you can also set the service name using the POWERTOOLS_SERVICE_NAME environment variable
// Learn more at: https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html

const lambdaHandler = async (event: typeof Events.Custom.CustomEvent, context: Context) => {
  // Add custom annotation & metadata
  tracer.putAnnotation('awsRequestId', context.awsRequestId);
  tracer.putMetadata('eventPayload', event);
  
  let res;
  try {
    res = { foo: 'bar' };
  } catch (err) {
    throw err;
  }
  
  return res;
}

// We instrument the handler with the Middy middleware and the Tracer will automatically:
// * handle the lifecycle of the subsegment
// * create a ColdStart annotation to easily filter traces that have had an initialization overhead
// * create a Service annotation to easily filter traces that have a specific service name
// * captures any response, or full exceptions generated by the handler, and include them as tracing metadata
export const handler = middy(lambdaHandler).use(captureLambdaHandler(tracer));