Google Cloud Function async with multiple fetch requests

I’m new to both GCF and Javascript async and have been struggling with this. I perform a fetch call initially and then pass that response as a parameter to a second function which then also performs a separate fetch call.

During the second function, my empty initialized json gets properties added to it, and when that function completes, I want to notify the exports.helloHttp to then do res.end and terminate.

I’ve tried chaining an additional empty then() but it doesn’t seem to be working.

My code:

var json = {}; // <- gets properties added to it during secondFunction()

exports.helloHttp = (req, res) => {
  fetch("firstfetchurl.com",requestOptions)
  .then(result => result.json())
  .then(response => {
    // next take the result and create a new product
    return secondFunction(response);
  })
  .catch(error => console.log('error', error));

  // res.end(JSON.stringify(json)); <- this is what I want my cloud function to output, but only after secondFunction completes        
};

Answer

Here is the code that would do what you want (replace the fetch URLs and set the appropriate options)

const fetch = require('node-fetch');

exports.helloHttp = async (req, res) => {
    return fetch("https://jsonplaceholder.typicode.com/users/1/albums") // First fetch
        .then(firstFetchResponse => firstFetchResponse.json())
        .then(firstFetchResponse => secondFunction(firstFetchResponse)) // Second fetch
        .then(secondFunctionResponse => secondFunctionResponse.json())
        .then(finalResponse => res.json(finalResponse)) // This line sends your response to the client
        .catch(error => { console.error('Error', error); res.status(500).send('Server Error') }); // In case an error, log and send an error response
};

async function secondFunction(data) {
    // Logic of your second function. Here just does another fetch using the data from the first request
    let firstAlbumId = data[0].id
    return fetch(`https://jsonplaceholder.typicode.com/albums/${firstAlbumId}/photos`);
}

The same function can use an await like this

exports.helloHttp = async (req, res) => {
    try {
        let response = await fetch("https://jsonplaceholder.typicode.com/users/1/albums") // Note the await on this line
            .then(result => result.json())
            .then(firstFetchResponse => secondFunction(firstFetchResponse))
            .then(secondFetchResponse => secondFetchResponse.json());
        res.json(response); // Finally you are sending the response here.
    } catch (error) {
        console.error(error);
        res.status(500).send('Server Error');
    }
};

Finally you would also need to make sure that the package.json has the dependency for node-fetch

{
  "name": "sample-http",
  "version": "0.0.1",
  "dependencies": {
    "node-fetch": "^2.6.0" // This line must be there
  }
}

For sending the JSON response, it uses this method.