Firebase Functions: Unclear "connection error"
Function execution took ****ms, finished with status: 'connection error'
or ECONNRESET
usually happens when a function doesn’t know whether a promise resolved or not.
Every promise must be returned, as mentioned in the docs here. There is also a blog post (with helpful video!) about this.
A couple of examples of unreturned promises:
exports.someFunc = functions.database.ref('/some/path').onCreate(event => {
let db = admin.database();
// UNRETURNED PROMISE
db.ref('/some/path').remove();
return db.ref('/some/other/path').set(event.data.val());
});
exports.makeUppercase = functions.database.ref('/hello/{pushId}').onWrite(event => {
return event.data.ref.set('world').then(snap => {
// UNRETURNED PROMISE
admin.database().ref('lastwrite').set(admin.database.ServerValue.TIMESTAMP);
});
});
exports.makeUppercase = functions.database.ref('/hello/{pushId}').onWrite(event => {
// UNRETURNED PROMISE
event.data.ref.set('world').then(snap => {
return admin.database().ref('lastwrite').set(admin.database.ServerValue.TIMESTAMP);
});
});
To help catch this mistake before deploying code, check out this eslint rule.
For an in-depth look at promises, here are some helpful resources:
- Mozilla docs
- Ponyfoo promises deep dive
- Links to the ECMA standard
- Egghead.io course
Even though this question has an approved answer, you may have followed the steps in that answer and still reached a point where the error was still occurring.
In that case, we were informed by GCP that there's a known issue with Node 8 CFs and this connection error, for which the workaround is to update the node version to 10.
Related github issue: https://github.com/firebase/firebase-functions/issues/429
Specific comment: https://github.com/firebase/firebase-functions/issues/429#issuecomment-577324193
I think it might be too many simultaneous firebase database connections :/ https://groups.google.com/forum/#!topic/firebase-talk/4RjyYIDqMVQ