firebase transaction on lower node - Maximum call stack size exceeded

问题

after several Q&A about the transaction mechanism I'm trying to run a transaction on a lowel node

here is my data:

activeOffers
    -LKohyZ58cnzn0vCnt9p
        details
            direction: "city"
            seatsCount: 2
            timeToGo: 5
        uid: "-ABSIFJ0vCnt9p8387a"    ---- offering user

I'm trying to run the transaction on -LKohyZ58cnzn0vCnt9p and do the following:

1. decrease the seatsCount by some requested value if there is enought seats
2. add a subnode deal under ** -LKohyZ58cnzn0vCnt9p** with the requested value and the uid of the requesting user.

But obviously I don't do it correctly because I get Maximum call stack size exceeded even only for step 1.

Here is my code:

(entryRef is the ref to -LKohyZ58cnzn0vCnt9p)

dealSeats = function(entryRef, data) {
    const TAG = '[dealSeats]: ';
    return entryRef.transaction((current)=>{
        if (current) {
            if (current.details.seatsCount >= data.details.seatsCount) {
                current.details.seatsCount -= data.details.seatsCount;
            }
        }
        return current;
    });
}

================ update after Frank van Puffelen's comment ===============

I don't see any recursion in my flow:

I call the cloud function in Postman sending the following data:

{
 "data": 
  {
     "uid": "-FGKKSDFGK12387sddd",    ---- the requesting/asking user
     "id": "-LKpCACQlL25XTWJ0OV_",
     "details":
     {
          "direction": "city",
          "seatsCount": 1,
          "timeToGo": 5
     }
  }
}

===== index.js =====

entries = require('./entries');

/// cloud function
exports.TEST_askOfferSeats = functions.https.onCall((data, context) => {
    console.log('data: ' + JSON.stringify(data));
    return entries.askSeats(data);
});

===== entries.js =======

exports.askSeats = function(data) {
    const TAG = '[askSeats]: ';

    var entryRef = db.ref('activeOffers/' + data.id);
    return globals.exists(entryRef)
        .then((found)=>{
            if (found) {
                return dealSeats(entryRef, data);
            } else {
                return 'Offer not found [' + data.id + ']';
            }
        });
}

and here is the stacktrace in the error log:

function:
  TEST_askOfferSeats
event message:
  Unhandled error RangeError: Maximum call stack size exceeded
      at Function.mapValues (/user_code/node_modules/firebase- 
  functions/node_modules/lodash/lodash.js:13395:23)
      at encode (/user_code/node_modules/firebase- 
  functions/lib/providers/https.js:204:18)
      at /user_code/node_modules/firebase- 
  functions/node_modules/lodash/lodash.js:13400:38
      at /user_code/node_modules/firebase- 
  functions/node_modules/lodash/lodash.js:4925:15
      at baseForOwn (/user_code/node_modules/firebase- 
  functions/node_modules/lodash/lodash.js:3010:24)
      at Function.mapValues (/user_code/node_modules/firebase- 
  functions/node_modules/lodash/lodash.js:13399:7)
      at encode (/user_code/node_modules/firebase- 
  functions/lib/providers/https.js:204:18)
      at /user_code/node_modules/firebase- 
  functions/node_modules/lodash/lodash.js:13400:38
      at /user_code/node_modules/firebase- 
  functions/node_modules/lodash/lodash.js:4925:15
      at baseForOwn (/user_code/node_modules/firebase- 
  functions/node_modules/lodash/lodash.js:3010:24)
      at Function.mapValues (/user_code/node_modules/firebase-         
  functions/node_modules/lodash/lodash.js:13399:7)

I don't have any triggers or something that could call again and again the same code...

回答1:

And finally it appeared to be very very stupid of me. If I wanted to use transaction returning a promise I should put

  .then((success)=>{   ...   }

after the transaction. i.e.:

 return entryRef.transaction((current)=>{
    if (current) {
        if (current.details.seatsCount >= data.details.seatsCount) {
            current.details.seatsCount -= data.details.seatsCount;
        }
    }
    return current;
})
.then((success)=> {
.......
});

And everything is fine now :)

来源：https://stackoverflow.com/questions/52043552/firebase-transaction-on-lower-node-maximum-call-stack-size-exceeded