aws-lambda-router

A small library for AWS Lambda providing routing for API Gateway Proxy Integrations and SNS.

Features

• Easy Handling of ANY method in API Gateways
• Simplifies writing lambda handlers (in nodejs)
• Lambda Proxy Resource support for AWS API Gateway
• Enable CORS for requests
• No external dependencies
• Currently there are two processors (callers for Lambda) implemented: API Gateway ANY method (called proxyIntegration), SNS and SQS.

Installation

Install via npm

$ npm install aws-lambda-router

or yarn

$ yarn install aws-lambda-router

Getting Started

This is a simple example of aws-lambda-router in conjunction with ANY method and the API Gateway proxy integration. The following code will respond with a message when executed using an AWS API Gateway with a GET request on URL path <base-url-of-gateway>/gateway-mapping/article/123.

const router = require('aws-lambda-router');

// handler for an api gateway event
exports.handler = router.handler({
    // for handling an http-call from an AWS API Gateway proxyIntegration we provide the following config:
    proxyIntegration: {
        routes: [
            {
                // request-path-pattern with a path variable:
                path: '/article/:id',
                method: 'GET',
                // we can use the path param 'id' in the action call:
                action: (request, context) => {
                    return "You called me with: " + request.paths.id;
                }
            }
        ]
    }
}

Enable CORS

To activate CORS on all http methods (OPTIONS requests are handled automatically) you only need to set the parameter cors to true on the proxyIntegration rule.

See the following example:

const router = require('aws-lambda-router');

exports.handler = router.handler({
    // for handling an http-call from an AWS Apigateway proxyIntegration we provide the following config:
    proxyIntegration: {
        cors: true,
        routes: [
            {
                path: '/graphql',
                method: 'POST',
                // provide a function to be called with the appropriate data
                action: (request, context) => doAnything(request.body)
            }
        ]
    }
});

If CORS is activated, these default headers will be sent on every response:

"Access-Control-Allow-Origin" = "'*'"
"Access-Control-Allow-Methods" = "'GET,POST,PUT,DELETE,HEAD,PATCH'"
"Access-Control-Allow-Headers" = "'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token'"

Errormapping

const router = require('aws-lambda-router');

exports.handler = router.handler({
    // for handling an http-call from an AWS Apigateway proxyIntegration we provide the following config:
    proxyIntegration: {
        routes: [
            {
                path: '/graphql',
                method: 'POST',
                action: (request, context) => doAnything(request.body)
            }
        ],
        debug: true,
        errorMapping: {
            'NotFound': 404,
            'ServerError': 500
        }
    }
});

With the key word errorMapping shown in the example above you can custom mapping of thrown errors to http response code error. The action can throw an object like

"throw {reason: 'NotFound', message: 'object id not found'}"

and the http response then contains the configured value as response code and the message as the body.

SNS to Lambda Integrations

For handling calls in Lambdas initiated from AWS-SNS you can use the following code snippet:

const router = require('aws-lambda-router');

exports.handler = router.handler({
    sns: {
        routes: [
            {
                // a regex to match the content of the SNS-Subject:
                subject: /.*/,
                // Attention: the message is JSON-stringified
                action: (sns, context) => service.doSomething(JSON.parse(sns.Message))
            }
        ]
    }
});

SQS to Lambda Integrations

For handling calls in Lambdas initiated from AWS-SQS you can use the following code snippet:

const router = require('aws-lambda-router');

exports.handler = router.handler({
    sqs: {
        routes: [
            {
                // match complete SQS ARN:
                source: 'arn:aws:sqs:us-west-2:594035263019:aticle-import',
                // Attention: the messages Array is JSON-stringified
                action: (messages, context) => messages.forEach(message => console.log(JSON.parse(message)))
            },
            {
                // a regex to match the source SQS ARN:
                source: /.*notification/,
                // Attention: the messages array is JSON-stringified
                action: (messages, context) => service.doNotify(messages)
            }
        ]
    }
});

An SQS message always contains an array of records. In each SQS record there is the message in the body JSON key. The action method gets all body elements from the router as an array.

If more than one route matches, only the first is used!

Custom response

Per default a status code 200 will be returned. This behavior can be overridden.

By providing a body property in the returned object you can modify the status code and response headers.

return {
        // Allow for custom status codes depending on execution.
        statusCode: 218,
        // Headers will merge with CORS headers when enabled.
        // Will merge with Content-Type: application/json
        headers: {
            'x-new-header': 'another-value'
        },
        // When returning a custom response object, a key of body is required
        // The value of body needs to be JSON stringified, this matches
        // the expected response for an AWS Lambda.
        body: JSON.stringify({
            foo: 'bar'
        })
    };

Local developement

The best is to work with yarn link

See here: https://yarnpkg.com/en/docs/cli/link

Release History

• 0.5.0 new feature: SQS route integration now available; bugfix: SNS integration now works woth Array of message instead of single message
• 0.4.0 now the Context Object pass through
• 0.3.1 proxyIntegration: avoid error if response object is not set; add some debug logging
• 0.3.0 proxyIntegration: add PATCH method; allow for custom status codes from route (thanks to @mintuz)
• 0.2.2 proxyIntegration: set correct header values now for CORS
• 0.2.1 proxyIntegration: CORS in Preflight, status code 400 for invalid body, set more CORS headers as default
• 0.2.0 Attention: breaking changes for configuration; add SNS event process
• 0.1.0 make it work now
• 0.0.1 initial release