Batched Write/Transaction in Cloud Function keeps failing - firebase

Question

I'm trying to make changes to several documents in a cloud function once I receive a callback. My code was working when I only had to update one document, but now I need to update several documents atomically in the same function.
I need to read a certain document and then update other documents based on the information held in an array in the original document. I tried to do this using forEach but I get this error in the console whether I'm using a transaction or a batched write:
Error: Cannot modify a WriteBatch that has been committed.
at WriteBatch.verifyNotCommitted (/workspace/node_modules/#google-cloud/firestore/build/src/write-batch.js:126:19)
at WriteBatch.update (/workspace/node_modules/#google-cloud/firestore/build/src/write-batch.js:315:14)
at loyaltyIds.forEach (/workspace/index.js:323:31)
at process._tickCallback (internal/process/next_tick.js:68:7)
Error: Process exited with code 16
at process.on.code (/layers/google.nodejs.functions-framework/functions-framework/node_modules/#google-cloud/functions-framework/build/src/invoker.js:92:22)
at process.emit (events.js:198:13)
at process.EventEmitter.emit (domain.js:448:20)
at process.exit (internal/process/per_thread.js:168:15)
at sendCrashResponse (/layers/google.nodejs.functions-framework/functions-framework/node_modules/#google-cloud/functions-framework/build/src/logger.js:44:9)
at process.on.err (/layers/google.nodejs.functions-framework/functions-framework/node_modules/#google-cloud/functions-framework/build/src/invoker.js:88:44)
at process.emit (events.js:198:13)
at process.EventEmitter.emit (domain.js:448:20)
at emitPromiseRejectionWarnings (internal/process/promises.js:140:18)
at process._tickCallback (internal/process/next_tick.js:69:34)
And what I end up with is the document outside the for loop is updated but the documents inside the for loop are not - which defeats the purpose of an atomic operation.
It also takes a long time to complete the write operation to Firestore. Where am I going wrong?
Below is what I've tried:
Using batched write:
const txDoc = await txRef.get();
if (txDoc.exists) {
console.log('Transaction Document Found');
const userId = txDoc.data().userId;
const loyaltyIds = txDoc.data().loyaltyIds;
const pointsAwardedMap = txDoc.data().pointsAwarded;
let batch = db.batch();
loyaltyIds.forEach(async lpId => {
// There are 2 elements in the loyaltyIds lis
console.log('Inside for loop');
console.log(lpId);
let cardId = 'u_' + userId + '-l_' + lpId; // 'u_$userId-l_$lpId'
let cardRef = db.collection('users').doc(userId).collection('userLoyaltyCards').doc(cardId);
let lpMap = pointsAwardedMap[lpId];
// Get the user LC doc
let cardDoc = await cardRef.get();
if (cardDoc.exists) {
batch.update(cardRef, {
'pointsBalance': cardDoc.data().pointsBalance + lpMap['points'],
'totalSpend': cardDoc.data().totalSpend + txDoc.data().transactionAmount,
'numberOfPurchases': cardDoc.data().numberOfPurchases + 1,
'pointsEarned': cardDoc.data().pointsEarned + lpMap['points'],
'lastPurchaseDate': admin.database.ServerValue.TIMESTAMP,
});
}
});
// Then we update the tx doc
batch.update(txRef, {
transactionCode: `${receiptNo}`,
transactionType: "purchase",
transactionSuccess: true,
}); // only this gets update
console.log('Firebase Transaction success');
return batch.commit();
} else { return null; }
Using transaction operation:
await db.runTransaction(async t => {
const txDoc = await t.get(txRef);
if (txDoc.exists) {
// userId
// For each lp we update the user loyalty card that goes with it
const userId = txDoc.data().userId;
const loyaltyIds = txDoc.data().loyaltyIds;
const pointsAwardedMap = txDoc.data().pointsAwarded;
// What the pointsAwarded map looks like from the transaction:
// var pointsAwarded = {
// lp1: {
// lpName: 'Jeff',
// lpId: 'lp.lpId',
// points: 'points1',
// cashbackPct: 'lp.cashbackPct',
// vendorId: 'lp.vendorId',
// vendorName: 'lp.vendorName',
// },
// lp2: {
// lpName: 'Susan',
// lpId: 'lp.lpId',
// points: 'points2',
// cashbackPct: 'lp.cashbackPct',
// vendorId: 'lp.vendorId',
// vendorName: 'lp.vendorName',
// },
// };
loyaltyIds.forEach(async (lpId) => {
// We update the user loyalty cards
console.log('Inside for loop');
console.log(lpId);
let cardId = 'u_' + userId + '-l_' + lpId; // 'u_$userId-l_$lpId'
let cardRef = db.collection('users').doc(userId).collection('userLoyaltyCards').doc(cardId);
let lpMap = pointsAwardedMap[lpId];
// Get the user LC doc
let cardDoc = await t.get(cardRef);
// We create the initial loyalty card doc without relying on the cloud function
if (cardDoc.exists) {
// Users LC found, we simply update with this transaction
// `${mpesaReceiptNo}`, this is how to add a var as a field value in firestore
t.update(cardRef, {
'pointsBalance': cardDoc.data().pointsBalance + lpMap['points'],
'totalSpend': cardDoc.data().totalSpend + txDoc.data().transactionAmount,
'numberOfPurchases': cardDoc.data().numberOfPurchases + 1,
'pointsEarned': cardDoc.data().pointsEarned + lpMap['points'],
'lastPurchaseDate': admin.database.ServerValue.TIMESTAMP,
});
}
}); // end of loyalty card update loop
// Then we update the transaction doc
console.log('Transaction Document Found')
t.update(txRef, {
transactionCode: `${mpesaReceiptNo}`,
transactionType: "purchase",
transactionSuccess: true,
});
console.log('Firebase Transaction success');
}
});
UPDATE
I've tried to use a normal for loop but I still get the same errors. I even tried to incorporate the batch.commit statement in the loop so it only executes when the loop completes. Still - same errors.
try {
return txRef.get().then( async txDoc => {
if (txDoc.exists) {
const userId = txDoc.data().userId;
const loyaltyIds = txDoc.data().loyaltyIds;
const pointsAwardedMap = txDoc.data().pointsAwarded;
const batch = db.batch();
// loyaltyIds.forEach(lpId => {
for (let i = 0; i < loyaltyIds.length; i++) {
// We update the user loyalty cards
const lpId = loyaltyIds[i];
console.log('Inside for loop');
console.log(lpId);
const cardId = 'u_' + userId + '-l_' + lpId; // 'u_$userId-l_$lpId'
const cardRef = db.collection('users').doc(userId).collection('userLoyaltyCards').doc(cardId);
const lpMap = pointsAwardedMap[lpId];
// Get the user LC doc
cardRef.get().then(cardDoc => {
// We created the initial loyalty card doc without relying on the cloud function
if (cardDoc.exists) {
console.log('Card found');
// Users LC found, we simply update with this transaction
// `${mpesaReceiptNo}`, this is how to add a var as a field value in firestore
batch.update(cardRef, {
'pointsBalance': cardDoc.data().pointsBalance + lpMap['points'],
'totalSpend': cardDoc.data().totalSpend + txDoc.data().transactionAmount,
'numberOfPurchases': cardDoc.data().numberOfPurchases + 1,
'pointsEarned': cardDoc.data().pointsEarned + lpMap['points'],
'lastPurchaseDate': admin.database.ServerValue.TIMESTAMP,
});
}
});
if (i + 1 == loyaltyIds.length) {
console.log('Loyalty card loop complete, now going to update other things and commit the batch.');
// Update the transaction document
batch.update(txRef, {
transactionCode: `${mpesaReceiptNo}`,
transactionType: "purchase",
transactionSuccess: true,
});
console.log('Committing the batch');
return batch.commit();
}
} // end of for loop
} else {
console.log('Transaction Doc not found, terminating function.');
return null;
}
}).then(function () {
console.log("SUCCESS")
return null;
}
).catch(function (error) {
console.log("UNABLE TO EXECUTE TX BATCH");
console.log(error);
// throw new functions.https.HttpsError('unknown', 'An error occurred when trying to sort the posts.');
return null;
});

Answer 1

I think your problem is related to promises. You must await for the batch.commit(), which was not done in your code. No need to use the await for batch.update(), only for the batch.commit().
Usage of the map with the Promise.all is very important here to ensure you await for all the loop operations to be completed.
I updated your code using awaits, I could not test it since I don't have access to your DB, but I think it should solve your problem with the batch.
try {
const txDoc = await txRef.get();
if (txDoc.exists) {
const userId = txDoc.data().userId;
const loyaltyIds = txDoc.data().loyaltyIds;
const pointsAwardedMap = txDoc.data().pointsAwarded;
const batch = db.batch();
await Promise.all(loyaltyIds.map(async (lpId, i) => {
console.log(lpId);
const cardId = 'u_' + userId + '-l_' + lpId; // 'u_$userId-l_$lpId'
const cardRef = db.collection('users').doc(userId).collection('userLoyaltyCards').doc(cardId);
const lpMap = pointsAwardedMap[lpId];
const cardDoc = await cardRef.get();
if (cardDoc.exists) {
batch.update(cardRef, {
'pointsBalance': cardDoc.data().pointsBalance + lpMap['points'],
'totalSpend': cardDoc.data().totalSpend + txDoc.data().transactionAmount,
'numberOfPurchases': cardDoc.data().numberOfPurchases + 1,
'pointsEarned': cardDoc.data().pointsEarned + lpMap['points'],
'lastPurchaseDate': admin.database.ServerValue.TIMESTAMP,
});
}
if (i + 1 == loyaltyIds.length) {
batch.update(txRef, {
transactionCode: `${mpesaReceiptNo}`,
transactionType: "purchase",
transactionSuccess: true,
});
}
}));
await batch.commit();
return null;
} else {
console.log('Transaction Doc not found, terminating function.');
return null;
}
} catch (error) {
console.log(error);
return null;
}