Race condition in documented counter implementation about nodejs-firestore HOT 2 CLOSED

The code within runTransaction is retried on contention. You should not write any logic that relies on how often it is executed. My guess as what to is happening here is that your transactions fail to commit, and hence we re-run your code, which explains the additional logging output. To determine whether a transaction was committed correctly, you can modify your code as such:

 return firestore.runTransaction(function (transaction) {
    var documentRef = firestore.doc(input.counter);
    return transaction.get(documentRef).then(function (doc) {
      if (doc.exists) {
        var count =  doc.get("count") || 0;
        if (count >= input.maxCount) {
          return Promise.resolve(count);
        }
        transaction.update(documentRef, { count: ++count });
        return Promise.resolve(count);
      }

      transaction.create(documentRef, { count: 1 });
      return Promise.resolve(1);
    });
  }).then(count => {
    console.log('Updated counter to ' + count);
  });

Please let us know if this helped resolve your issue.

from nodejs-firestore.

Hoo, tricky.

Okay, I've updated my test code and it seems to be working as expected now. I'm gonna revisit my application's logic.

Thanks for your valuable response. It would be nice if the doc could include this information!

from nodejs-firestore.