Lambda function returning a promise from a function not working

Question

I am working on lambda function using node js. I calling a function which return a promise on then I am calling a promiseAll. My first function gets a row form DB based on ID, if row is not present I want to return error response and if present it should call promiseAll.

Following is my code:

return getDetailsOfRow(id).then(function() {
    return Promise.all([
        getDetailsOfA(query1), 
        getDetailsOfB(query2), 
        getDetailsOfC(tripLocationsQuery)
    ]).then(function(values) {
        return combineResults();
    })
});

function getDetailsOfRow(trip) {
    return new Promise((resolve, reject) => {
        con.query(query, id, (err, results, fields) => {
            if (err) {
                reject(err);
            }
            if (results.length < 1) {
                createErrorResponse();
            } else {
                //get the set column values to use for other function   
            }
        });
    });
}

function createErrorResponse() {
    return new Promise((resolve, reject) => {
        var response = {
            "isBase64Encoded": false,
            "statusCode": 404,
            "headers": {
                "Content-Type": "text/html"
            },
            "body": "Invalid Key"
        };
        resolve(response);
    });
}

promise inside createErrorResponse method is not getting called for lambda function. I am not getting any response from a lambda function. I didn't find any solution. Is it because I will br returning a promise inside a promise if call createErrorResponse() from getDetailsOfRow() ?

Sohail Ashraf · Accepted Answer · 2020-02-13 09:24:30Z

1

You don't need to wrap createErrorResponse function in a promise.

Add the createErrorResponse() in resolve or reject and add catch block in getDetailsOfRow to catch the error.

Try this


return getDetailsOfRow(id).then(function() {
  return Promise.all([
    getDetailsOfA(query1),
    getDetailsOfB(query2),
    getDetailsOfC(tripLocationsQuery)
  ]).then(function(values) {
    return combineResults();
  }).catch( error => {
     return error;
  });
});

function getDetailsOfRow(trip) {
  return new Promise((resolve, reject) => {
    con.query(query, id, (err, results, fields) => {
      if (err) {
        reject(err);
      }
      if (results.length < 1) {
        reject(createErrorResponse());
      } else {
        //get the set column values to use for other function
      }
    });
  });
}

function createErrorResponse() {
  return {
    isBase64Encoded: false,
    statusCode: 404,
    headers: {
      "Content-Type": "text/html"
    },
    body: "Invalid Key"
  };
}

edited Feb 13, 2020 at 9:24

answered Feb 13, 2020 at 9:18

Sohail Ashraf

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3 Comments

Sonali Over a year ago

I am not getting any error but I am not getting any response also

Sonali Over a year ago

Sohail I can see { "errorType": "Error", "errorMessage": "[object Object]", "stack": [ "Error: [object Object]", " at _homogeneousError (/var/runtime/CallbackContext.js:13:12)", " at postError (/var/runtime/CallbackContext.js:30:51)", " at done (/var/runtime/CallbackContext.js:57:7)", " at fail (/var/runtime/CallbackContext.js:69:7)", " at /var/runtime/CallbackContext.js:105:16", " at process._tickCallback (internal/process/next_tick.js:68:7)" ] } error in cloud watch logs

Sohail Ashraf Over a year ago

Console log in the catch block and see what is the error.

Ashish Modi · Accepted Answer · 2020-02-13 11:53:45Z

0

I see two problems here

You are wrapping the code for createErrorResponse in promise which is not required.
You are not resolving in getDetailsOfRow method so there is no way to fulfill the promise.

The code should look like this

return getDetailsOfRow(id).then(function() {
  return Promise.all([
    getDetailsOfA(query1),
    getDetailsOfB(query2),
    getDetailsOfC(tripLocationsQuery)
  ]).then(function(values) {
    return combineResults();
  }).catch( error => {
     return error;
  });
});

function getDetailsOfRow(trip) {
  return new Promise((resolve, reject) => {
    con.query(query, id, (err, results, fields) => {
      if (err) {
        reject(err);
      }
      if (results.length < 1) {
        reject(createErrorResponse());
      } else {
        resolve(results); // it should be resolved.
      }
    });
  });
}

function createErrorResponse() {
  return {
    isBase64Encoded: false,
    statusCode: 404,
    headers: {
      "Content-Type": "text/html"
    },
    body: "Invalid Key"
  };
}

answered Feb 13, 2020 at 11:53

Ashish Modi

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3 Comments

Sonali Over a year ago

I am resolving the promise with result I get in getDetailsOfRow

Sonali Over a year ago

can see { "errorType": "Error", "errorMessage": "[object Object]", "stack": [ "Error: [object Object]", " at _homogeneousError (/var/runtime/CallbackContext.js:13:12)", " at postError (/var/runtime/CallbackContext.js:30:51)", " at done (/var/runtime/CallbackContext.js:57:7)", " at fail (/var/runtime/CallbackContext.js:69:7)", " at /var/runtime/CallbackContext.js:105:16", " at process._tickCallback (internal/process/next_tick.js:68:7)" ] } error in cloud watch logs

Ashish Modi Over a year ago

it is hard to undersrtand from this. can you stringify errorMessage?

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