@miermontoto/lambda-handler

Base handler class for AWS Lambda with middleware support and health checks. Simplifies Lambda development with routing, error handling, warmup support, and common utilities for parsing requests.

Installation

pnpm add @miermontoto/lambda-handler

Configuration

interface HandlerConfig {
  healthCheckPath?: string;   // default '/health'
  enableCors?: boolean;       // default true
  enableLogging?: boolean;    // default true
  warmupPath?: string;       // path for warmup events
}

Usage

Basic Handler Class

import { BaseHandler } from '@miermontoto/lambda-handler';
import { badRequest, ok } from '@miermontoto/lambda-responses';

class MyHandler extends BaseHandler {
  constructor() {
    super({
      healthCheckPath: '/health',
      enableLogging: true,
    });
  }

  protected async handleRoutes(event, context, callback) {
    const path = event.rawPath;
    const method = event.requestContext.http.method;

    if (path === '/users' && method === 'GET') {
      return ok({ users: [] });
    }

    if (path === '/users' && method === 'POST') {
      const body = JSON.parse(event.body || '{}');
      return ok({ created: body });
    }

    return badRequest('Route not found');
  }
}

export const handler = new MyHandler().handler;

Simple Handler

import { createHandler, parseBody } from '@miermontoto/lambda-handler';
import { ok, badRequest } from '@miermontoto/lambda-responses';

export const handler = createHandler(async (event) => {
  const body = parseBody(event);

  if (!body) {
    return badRequest('Body required');
  }

  // process request
  return ok({ processed: body });
});

With Middleware

import { BaseHandler } from '@miermontoto/lambda-handler';

class MyHandler extends BaseHandler {
  constructor() {
    super();

    // add authentication middleware
    this.use(async (event, context, next) => {
      const token = event.headers.authorization;

      if (!token) {
        return unauthorized('Token required');
      }

      // validate token...
      return next();
    });

    // add logging middleware
    this.use(async (event, context, next) => {
      console.log('Request:', event.rawPath);
      const result = await next();
      console.log('Response:', result.statusCode);
      return result;
    });
  }

  protected async handleRoutes(event, context, callback) {
    // your routes here
  }
}

Error Handling

class MyHandler extends BaseHandler {
  constructor() {
    super();

    // set custom error handler
    this.setErrorHandler((error, event, context) => {
      console.error('Custom error handler:', error);

      if (error.name === 'ValidationError') {
        return badRequest(error.message);
      }

      return serverError('Something went wrong');
    });
  }
}

Helper Functions

• parseBody(event) - Parse JSON body from event
• getQueryParams(event) - Get query string parameters
• getPathParams(event) - Get path parameters
• getHeaders(event) - Get request headers
• getHttpMethod(event) - Get HTTP method
• getPath(event) - Get request path
• isWarmupEvent(event) - Check if it's a warmup event
• isHealthCheck(event, path) - Check if it's a health check

License

CC BY-NC-ND 4.0