How to test AWS Lambda handler locally using NodeJS?
This is what I did:
index.js
exports.handler = async (event) => { console.log('hello world'); const response = { statusCode: 200, body: JSON.stringify('Hello from Lambda!') }; return response;};package.json
"scripts": { "locally": "node -e \"console.log(require('./index').handler(require('./event.json')));\""}event.json
{ "Records": [ { "eventVersion": "2.0", "eventSource": "aws:s3", "awsRegion": "eu-central-1", "eventTime": "1970-01-01T00:00:00.000Z", "eventName": "ObjectCreated:Put", "userIdentity": { "principalId": "AIDAJDPLRKLG7UEXAMPLE" }, "requestParameters": { "sourceIPAddress": "127.0.0.1" }, "responseElements": { "x-amz-request-id": "C3D13FE58DE4C810", "x-amz-id-2": "FMyUVURIY8/IgAtTv8xRjskZQpcIZ9KG4V5Wp6S7S/JRWeUWerMUE5JgHvANOjpD" }, "s3": { "s3SchemaVersion": "1.0", "configurationId": "testConfigRule", "bucket": { "name": "my-bucket", "ownerIdentity": { "principalId": "A3NL1KOZZKExample" }, "arn": "arn:aws:s3:::my-bucket" }, "object": { "key": "HelloWorld.jpg", "size": 1024, "eTag": "d41d8cd98f00b204e9800998ecf8427e", "versionId": "096fKKXTRTtl3on89fVO.nfljtsv6qko" } } } ]}Shell
npm run locallyOutput
> node -e "console.log(require('./index').handler({}));"hello worldPromise { { statusCode: 200, body: '"Hello from Lambda!"' } }
You need to call your handler function from another file lets say testHandler.js in order to run via NodeJs.
This will be done like this
//import your handler file or main file of Lambdalet handler = require('./handler');//Call your exports function with required params//In AWS lambda these are event, content, and callback//event and content are JSON object and callback is a function//In my example i'm using empty JSONhandler.handlerEvent( {}, //event {}, //content function(data,ss) { //callback function with two arguments console.log(data); });Now you can use node testHandler.js to test your handler function.
EDIT: Sample Event and content data as requested
Event:
{ "resource": "/API/PATH", "path": "/API/PATH", "httpMethod": "POST", "headers": { "Accept": "*/*", "Accept-Encoding": "gzip, deflate, br", "Accept-Language": "en-GB,en-US;q=0.9,en;q=0.8", "cache-control": "no-cache", "CloudFront-Forwarded-Proto": "https", "CloudFront-Is-Desktop-Viewer": "true", "CloudFront-Is-Mobile-Viewer": "false", "CloudFront-Is-SmartTV-Viewer": "false", "CloudFront-Is-Tablet-Viewer": "false", "CloudFront-Viewer-Country": "IN", "content-type": "application/json", "Host": "url.us-east-1.amazonaws.com", "origin": "chrome-extension://fhbjgbiflinjbdggehcddcbncdddomop", "User-Agent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36", "Via": "2.0 XXXXXXXXXXXXXX.cloudfront.net (CloudFront)", "X-Amz-Cf-Id": "XXXXXXXXXX51YYoOl75RKjAWEhCyna-fuQqEBjSL96TMkFX4H0xaZQ==", "X-Amzn-Trace-Id": "Root=1-XXX03c23-25XXXXXX948c8fba065caab5", "x-api-key": "SECUREKEY", "X-Forwarded-For": "XX.XX.XXX.XXX, XX.XXX.XX.XXX", "X-Forwarded-Port": "443", "X-Forwarded-Proto": "https" }, "multiValueHeaders": { "Accept": [ "*/*" ], "Accept-Encoding": [ "gzip, deflate, br" ], "Accept-Language": [ "en-GB,en-US;q=0.9,en;q=0.8" ], "cache-control": [ "no-cache" ], "CloudFront-Forwarded-Proto": [ "https" ], "CloudFront-Is-Desktop-Viewer": [ "true" ], "CloudFront-Is-Mobile-Viewer": [ "false" ], "CloudFront-Is-SmartTV-Viewer": [ "false" ], "CloudFront-Is-Tablet-Viewer": [ "false" ], "CloudFront-Viewer-Country": [ "IN" ], "content-type": [ "application/json" ], "Host": [ "apiurl.us-east-1.amazonaws.com" ], "origin": [ "chrome-extension://fhbjgbiflinjbdggehcddcbncdddomop" ], "User-Agent": [ "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36" ], "Via": [ "2.0 XXXXXXXXXXXXXX.cloudfront.net (CloudFront)" ], "X-Amz-Cf-Id": [ "XXXXXXXXXhCyna-fuQqEBjSL96TMkFX4H0xaZQ==" ], "X-Amzn-Trace-Id": [ "Root=1-XXXXXXX67339948c8fba065caab5" ], "x-api-key": [ "SECUREAPIKEYPROVIDEDBYAWS" ], "X-Forwarded-For": [ "xx.xx.xx.xxx, xx.xxx.xx.xxx" ], "X-Forwarded-Port": [ "443" ], "X-Forwarded-Proto": [ "https" ] }, "queryStringParameters": null, "multiValueQueryStringParameters": null, "pathParameters": null, "stageVariables": null, "requestContext": { "resourceId": "xxxxx", "resourcePath": "/api/endpoint", "httpMethod": "POST", "extendedRequestId": "xxXXxxXXw=", "requestTime": "29/Nov/2018:19:21:07 +0000", "path": "/env/api/endpoint", "accountId": "XXXXXX", "protocol": "HTTP/1.1", "stage": "env", "domainPrefix": "xxxxx", "requestTimeEpoch": 1543519267874, "requestId": "xxxxxxx-XXXX-xxxx-86a8-xxxxxa", "identity": { "cognitoIdentityPoolId": null, "cognitoIdentityId": null, "apiKey": "SECUREAPIKEYPROVIDEDBYAWS", "cognitoAuthenticationType": null, "userArn": null, "apiKeyId": "xxXXXXxxxxxx", "userAgent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36", "accountId": null, "caller": null, "sourceIp": "xx.xxx.xxx.xxx", "accessKey": null, "cognitoAuthenticationProvider": null, "user": null }, "domainName": "url.us-east-1.amazonaws.com", "apiId": "xxxxx" }, "body": "{\n \"city\": \"Test 1 City\",\n \"state\": \"NY\",\n \"zipCode\": \"11549\"\n}", "isBase64Encoded": false}Content:
{ "callbackWaitsForEmptyEventLoop": true, "logGroupName": "/aws/lambda/lambda-name", "logStreamName": "2018/11/29/[$LATEST]xxxxxxxxxxxb", "functionName": "lambda-name", "memoryLimitInMB": "1024", "functionVersion": "$LATEST", "invokeid": "xxxxx-xxx-11e8-xxx-xxxxxxxf9", "awsRequestId": "xxxxxx-xxxxx-11e8-xxxx-xxxxxxxxx", "invokedFunctionArn": "arn:aws:lambda:us-east-1:xxxxxxxx:function:lambda-name"}
In your index.js, just defined and exported a handler function, but no one calls it. In the Lambda environment, some AWS code will call this handler with message. In your local environment, you have to call your handler by yourself.
You could also have a look of this doc, it is a way to "simulate" Lambda in local environment.