Firebase cloud functions is very slow

Question

We're working on an application that uses the new firebase cloud functions. What currently is happening is that a transaction is put in the queue node. And then the function removes that node and puts it in the correct node. This has been implemented because of the ability to work offline.

Our current problem is the speed of the function. The function itself takes about 400ms, so that's alright. But sometimes the functions take a very long time (around 8 seconds), while the entry was already added to the queue.

We suspect that the server takes time to boot up, because when we do the action once more after the first. It takes way less time.

Is there any way to fix this problem? Down here i added the code of our function. We suspect there's nothing wrong with it, but we added it just in case.

const functions = require('firebase-functions');
const admin = require('firebase-admin');
const database = admin.database();

exports.insertTransaction = functions.database
    .ref('/userPlacePromotionTransactionsQueue/{userKey}/{placeKey}/{promotionKey}/{transactionKey}')
    .onWrite(event => {
        if (event.data.val() == null) return null;

        // get keys
        const userKey = event.params.userKey;
        const placeKey = event.params.placeKey;
        const promotionKey = event.params.promotionKey;
        const transactionKey = event.params.transactionKey;

        // init update object
        const data = {};

        // get the transaction
        const transaction = event.data.val();

        // transfer transaction
        saveTransaction(data, transaction, userKey, placeKey, promotionKey, transactionKey);
        // remove from queue
        data[`/userPlacePromotionTransactionsQueue/${userKey}/${placeKey}/${promotionKey}/${transactionKey}`] = null;

        // fetch promotion
        database.ref(`promotions/${promotionKey}`).once('value', (snapshot) => {
            // Check if the promotion exists.
            if (!snapshot.exists()) {
                return null;
            }

            const promotion = snapshot.val();

            // fetch the current stamp count
            database.ref(`userPromotionStampCount/${userKey}/${promotionKey}`).once('value', (snapshot) => {
                let currentStampCount = 0;
                if (snapshot.exists()) currentStampCount = parseInt(snapshot.val());

                data[`userPromotionStampCount/${userKey}/${promotionKey}`] = currentStampCount + transaction.amount;

                // determines if there are new full cards
                const currentFullcards = Math.floor(currentStampCount > 0 ? currentStampCount / promotion.stamps : 0);
                const newStamps = currentStampCount + transaction.amount;
                const newFullcards = Math.floor(newStamps / promotion.stamps);

                if (newFullcards > currentFullcards) {
                    for (let i = 0; i < (newFullcards - currentFullcards); i++) {
                        const cardTransaction = {
                            action: "pending",
                            promotion_id: promotionKey,
                            user_id: userKey,
                            amount: 0,
                            type: "stamp",
                            date: transaction.date,
                            is_reversed: false
                        };

                        saveTransaction(data, cardTransaction, userKey, placeKey, promotionKey);

                        const completedPromotion = {
                            promotion_id: promotionKey,
                            user_id: userKey,
                            has_used: false,
                            date: admin.database.ServerValue.TIMESTAMP
                        };

                        const promotionPushKey = database
                            .ref()
                            .child(`userPlaceCompletedPromotions/${userKey}/${placeKey}`)
                            .push()
                            .key;

                        data[`userPlaceCompletedPromotions/${userKey}/${placeKey}/${promotionPushKey}`] = completedPromotion;
                        data[`userCompletedPromotions/${userKey}/${promotionPushKey}`] = completedPromotion;
                    }
                }

                return database.ref().update(data);
            }, (error) => {
                // Log to the console if an error happened.
                console.log('The read failed: ' + error.code);
                return null;
            });

        }, (error) => {
            // Log to the console if an error happened.
            console.log('The read failed: ' + error.code);
            return null;
        });
    });

function saveTransaction(data, transaction, userKey, placeKey, promotionKey, transactionKey) {
    if (!transactionKey) {
        transactionKey = database.ref('transactions').push().key;
    }

    data[`transactions/${transactionKey}`] = transaction;
    data[`placeTransactions/${placeKey}/${transactionKey}`] = transaction;
    data[`userPlacePromotionTransactions/${userKey}/${placeKey}/${promotionKey}/${transactionKey}`] = transaction;
}

Answer 1

firebaser here

It sounds like you're experiencing a so-called cold start of the function.

When your function hasn't been executed in some time, Cloud Functions puts it in a mode that uses fewer resources. Then when you hit the function again, it restores the environment from this mode. The time it takes to restore consists of a fixed cost (e.g. restore the container) and a part variable cost (e.g. if you use a lot of node modules, it may take longer).

We're continually monitoring the performance of these operations to ensure the best mix between developer experience and resource usage. So expect these times to improve over time.

The good news is that you should only experience this during development. Once your functions are being frequently triggered in production, chances are they'll hardly ever hit a cold start again.