Ytukyg

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

let url = 'something.com';



module.exports = function(context) {

  let a = fetch(url)



  a.then(res => {

    if(res.status!=200) throw new Error(res.statusText)

    else{

      context.done(null, res.body);

    }

  });

  a.catch(err => {

      console.log(err)

      throw new Error(err)

  });



};

I have a durable function that calls an activity function like above. I have set automatic retry on failure on this activity function. To retry the function needs to get an error.

So In get request I want to throw an error when i get response like 404 or something similar. But when i throw from catch block i get an error like below

UnhandledPromiseRejectionWarning: Unhandled promise rejection. This
error originated either by throwing inside of an async function
without a catch block, or by rejecting a promise which was not handled
with .catch().

function pauses there and stops execution.I have to manually stop and start the execution. How can i handle this so that the function retries?

Your code branches.

Ignoring the detail, what you have is :

let a = <Promise>; // root

a.then(...); // branch_1

a.catch(...); // branch_2

So whereas you catch errors arising in a, any error arising in branch 1 will be uncaught. Hence the warning

Compare that with :

let a = <Promise>; // root

a.then(...).catch(...); // branch

or

<Promise>.then(...).catch(...); // no assignment necessary

So, you might write :

module.exports = function(context) {

    return fetch(url)

    .then(res => {

        if(res.status!=200) {

            throw new Error(res.statusText);

        } else {

            context.done(null, res.body);

        }

    })

    .catch(err => {

        console.log(err)

        throw new Error(err)

    });

};

Alternatively, depending on the required division of responsibilities between module and caller(s) ...

module.exports = function(context) {

    return fetch(url)

    .then(res => {

        if(res.status!=200) {

            throw new Error(res.statusText);

        } else {

            return res;

        }

    });

};

... and call .context.done(null, res.body); in a .then() callback in the caller.

In both cases, with return included, then the caller will need to catch errors otherwise you will again get an unhandled error warning.

Found that with the use of async/await this problem goes away and the function re-try after exception is thrown.

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

let url = 'something.com';



module.exports = async function(context) {



  let res = await fetch(url)



  if(res.status!=200) throw new Error(res.statusText);

  else return res.body;



};