How to http status code when return promise in lambda?

Question

Below is my lambda function. It returns a promise instead using the callback. I wonder how I can return different http status code to API gateway?

exports.handler = async (event, context) => {

    return new Promise((resolve, reject) => {
        const options = {
            ...
        };

        const req = http.request(options, (res) => {
          resolve('Success');
        });

        req.on('error', (e) => {
          reject(e.message);
        });

        // send the request
        req.write('');
        req.end();
    });
};

Set up Lambda Proxy Integrations on API gateway and then code to give response in lambda. — James Dean
– James Dean, Commented May 19, 2019 at 11:33

mayank nayyar · Accepted Answer · 2019-05-19 09:34:13Z

With the new Node.js 8.10 runtime, there are new handler types that can be declared with the “async” keyword or can return a promise directly.

The new handler types are alternatives to the callback pattern, which is still fully supported.

As pointed out in the other answer, either you can directly return the status code with the help of using “async” keyword or you can return the promise directly. Please refer to the undermentioned code which directly returns the promise from the lambda function.

exports.handler = (event, context) => {
    return new Promise ((resolve, reject) => {
        resolve()
    })
    .then (()=>{
        return {
            statusCode : 200
        }
    })
    .catch(() =>{
        return {
            statusCode : 400
        }
    })
}

Also, please refer to the undermentioned link that gives the in detail idea about how promises and async-await eliminates the callback based approach.

https://aws.amazon.com/blogs/compute/node-js-8-10-runtime-now-available-in-aws-lambda/

Melbourne2991 · Accepted Answer · 2019-05-19 09:02:55Z

0

There is no need to return a promise as the async keyword will do that for you:

exports.handler = async (event, context) => {
   return {
        statusCode: 201, // or whatever status code you want
        headers: {},
        body: JSON.stringify({})
    };
}

answered May 19, 2019 at 9:02

Melbourne2991

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