将 Firebase Function 转换为异步/等待

Question

The code below is writing only the header file to the csv file(what is outputted). I am assuming it is because the "get" requests within the function are asynchronous and therefore the function is not waiting for the data to be retrieved etc. How can I refactor this to await the result of the second forEach loop?

newApp.get('/createUtilCSV', (req, res) => {

    try {
        const tempFilePath = path.join(os.tmpdir(), "Util_" + req.query.start + "<->" + req.query.end + ".csv");

        var fromDate = new Date(req.query.start)
        var toDate = new Date(req.query.end)

        var fromD = admin.firestore.Timestamp.fromDate(fromDate);
        var toD = admin.firestore.Timestamp.fromDate(toDate);
        
        firestore.collection('utilisation')
            .where("timestamp", ">=", fromD)
            .where("timestamp", "<=", toD)
            .get()
            .then(snapshot => {

                var output = fs.createWriteStream(tempFilePath);
                var archive = archiver('zip', {
                    gzip: true,
                    zlib: {
                        level: 9
                    }
                });

                var utilText = "App Version,Author,Building,City,Country,Date,Floor ID,Floor Name, Floor Region,Bookable,Business Unit,Capacity,Fixed,Furniture Height,Occupancy,Position X,Position Y,Restricted,Status Date,Status Type,Unique Ref,Workspace Type,Report ID\n";
                let utils = snapshot.docs;
                console.log("util info: " + utils);
                utils.forEach(doc => {
                    var line = doc.data();
                    var utilLine = "";
                    utilLine = utilLine + line.appVersion + ",";
                    utilLine = utilLine + line.authorEmail + ",";
                    utilLine = utilLine + line.building + ",";
                    utilLine = utilLine + line.city + ",";
                    utilLine = utilLine + line.country + ",";
                    utilLine = utilLine + line.timestamp.toDate() + ",";
                    utilLine = utilLine + line.floorId + ",";
                    utilLine = utilLine + line.floorName + ",";
                    utilLine = utilLine + line.region + ",";

                    firestore.collection('utilisation')
                    .doc(line.documentID)
                    .collection('workspaces')
                    .get()
                    .then( snap => {
                            let workspaces = snap.docs;
                            workspaces.forEach(space => {

                            var lineSpace = space.data();
                            var spaceAdd = utilLine;
                            spaceAdd = spaceAdd + lineSpace.bookable + ",";
                            spaceAdd = spaceAdd + lineSpace.businessUnit + ",";
                            spaceAdd = spaceAdd + lineSpace.capacity + ",";
                            spaceAdd = spaceAdd + lineSpace.fixed + ",";
                            spaceAdd = spaceAdd + lineSpace.height + ",";
                            spaceAdd = spaceAdd + lineSpace.occupancy + ",";
                            spaceAdd = spaceAdd + lineSpace.positionX + ",";
                            spaceAdd = spaceAdd + lineSpace.positionY + ",";
                            spaceAdd = spaceAdd + lineSpace.restricted + ",";
                            spaceAdd = spaceAdd + lineSpace.statusDate.toDate() + ",";
                            spaceAdd = spaceAdd + lineSpace.statusType + ",";
                            spaceAdd = spaceAdd + lineSpace.uniqueRef + ",";
                            spaceAdd = spaceAdd + lineSpace.workspaceType + ",";
                            spaceAdd = spaceAdd + line.documentID + "\n";
                            utilText = utilText + spaceAdd;
                        });
                    });
                });
                try {

                    // listen for all archive data to be written
                    // 'close' event is fired only when a file descriptor is involved
                    output.on('close', function() {
                        console.log(archive.pointer() + ' total bytes');
                        console.log('archiver has been finalized and the output file descriptor has closed.');
                        console.log("Util Text: " + utilText);

                        bucket.upload(tempFilePath, {
                            make_public: true,
                            gzip: true,
                            destination: tempFilePath,

                            metadata: metadata,
                        });

                        //Let's get the signed URL
                        const file = admin.storage().bucket().file(tempFilePath);
                        console.log('File: ' + file);
                        var expiryDate = new Date();
                        expiryDate.setDate(expiryDate.getDate() + 1);
                        file.getSignedUrl({
                            action: 'read',
                            expires: expiryDate
                        }).then(urls => {
                            const signedUrl = urls[0];
                            console.log('Send: ' + signedUrl);
                            res.redirect(signedUrl);
                            res.end();
                        });
                    });

                    output.on('end', function() {
                        console.log('Data has been drained');
                    });

                    // good practice to catch warnings (ie stat failures and other non-blocking errors)
                    archive.on('warning', function(err) {
                        if (err.code === 'ENOENT') {
                            // log warning
                        } else {
                            // throw error
                            throw err;
                        }
                    });

                    // good practice to catch this error explicitly
                    archive.on('error', function(err) {
                        throw err;
                    });
                    const metadata = {
                        contentType: "application/zip",
                    };
                    archive.pipe(output);
                    // append a file from string
                    archive.append(utilText, {
                        name: tempFilePath
                    });
                    archive.finalize();
                    console.log("tempFilePath: " + tempFilePath);

                    console.log("Export Util CSV finished");
                } catch (err) {
                    console.log(err);
                }
            })
            .catch(err => console.log(err));
    } catch (error) {
        console.log("Export error:" + error);

    };
});

Answer 1

You could enclose it on an async function and use await . If you want to read the files in sequence, you cannot use forEach . Just use a modern for … of loop instead, in which await will work as expected:

const utilisation = async () => {
    let utilisationRef = db.collection('utilisation')
    .where("timestamp", ">=", fromD)
    .where("timestamp", "<=", toD)
    let allUtilisations = await utilisationRef.get();

    // ... some code

    for(const doc of allUtilisations.docs){
        console.log(doc.data());
        // ... some code
    }
}

utilisation();

or you can even use .map :

const utilisation = async () => {
    let utilisationRef = db.collection('utilisation')
    .where("timestamp", ">=", fromD)
    .where("timestamp", "<=", toD)
    let allUtilisations = await utilisationRef.get();
    const documents = allUtilisations.docs.map((doc) => ({ id: doc.id, ...doc.data() }));
    // ... some code

    for(const doc of documents){
        console.log(doc);
        // ... some code
    }
}

utilisation();

From the above code, you can now refactor your code and even for your second loop.

Answer 2

Thanks to all those with advice. I have refined this code and the following works now as expected:

 async function utilCSV(req, res) { const tempFilePath = path.join(os.tmpdir(), "Util_" + req.query.date + ".csv"); const minDate = new Date(req.query.date + " 00:00:00"); const maxDate = new Date(req.query.date + " 23:59:59"); const minTimestamp = admin.firestore.Timestamp.fromDate(minDate) const maxTimestamp = admin.firestore.Timestamp.fromDate(maxDate) const city = req.query.city; var output = fs.createWriteStream(tempFilePath); var archive = archiver('zip', { gzip: true, zlib: { level: 9 } }); const snapshot = await firestore.collection("utilisation").where("timestamp", ">", minTimestamp).where("timestamp", "<", maxTimestamp).get(); var utilText = "App Version,Author,Building,City,Country,Date,Floor ID,Floor Name, Floor Region,Bookable,Business Unit,Capacity,Fixed,Furniture Height,Occupancy,Position X,Position Y,Restricted,Status Date,Status Type,Unique Ref,Workspace Type,Report ID\n"; let utils = snapshot.docs; console.log("util info: " + utils); for (const doc of utils) { var line = doc.data(); var utilLine = ""; utilLine = utilLine + line.appVersion + ","; utilLine = utilLine + line.authorEmail + ","; utilLine = utilLine + line.building + ","; utilLine = utilLine + line.city + ","; utilLine = utilLine + line.country + ","; utilLine = utilLine + line.timestamp.toDate() + ","; utilLine = utilLine + line.floorId + ","; utilLine = utilLine + line.floorName + ","; utilLine = utilLine + line.region + ","; let spacesRef = firestore.collection('utilisation').doc(line.documentID).collection('workspaces'); const snap = await spacesRef.get(); let workspaces = snap.docs; for (const space of workspaces) { var lineSpace = space.data(); var spaceAdd = utilLine; spaceAdd = spaceAdd + lineSpace.bookable + ","; spaceAdd = spaceAdd + lineSpace.businessUnit + ","; spaceAdd = spaceAdd + lineSpace.capacity + ","; spaceAdd = spaceAdd + lineSpace.fixed + ","; spaceAdd = spaceAdd + lineSpace.height + ","; spaceAdd = spaceAdd + lineSpace.occupancy + ","; spaceAdd = spaceAdd + lineSpace.positionX + ","; spaceAdd = spaceAdd + lineSpace.positionY + ","; spaceAdd = spaceAdd + lineSpace.restricted + ","; spaceAdd = spaceAdd + lineSpace.statusDate.toDate() + ","; spaceAdd = spaceAdd + lineSpace.statusType + ","; spaceAdd = spaceAdd + lineSpace.uniqueRef + ","; spaceAdd = spaceAdd + lineSpace.workspaceType + ","; spaceAdd = spaceAdd + line.documentID + "\n"; utilText = utilText + spaceAdd; }; }; console.log("Complete string: " + utilText); try { // listen for all archive data to be written // 'close' event is fired only when a file descriptor is involved output.on('close', function () { console.log(archive.pointer() + ' total bytes'); console.log('archiver has been finalized and the output file descriptor has closed.'); console.log("Util Text: " + utilText); bucket.upload(tempFilePath, { make_public: true, gzip: true, destination: tempFilePath, metadata: metadata, }); //Let's get the signed URL const file = admin.storage().bucket().file(tempFilePath); console.log('File: ' + file); var expiryDate = new Date(); expiryDate.setDate(expiryDate.getDate() + 1); file.getSignedUrl({ action: 'read', expires: expiryDate }).then(urls => { const signedUrl = urls[0]; console.log('Send: ' + signedUrl); res.redirect(signedUrl); res.end(); }); }); output.on('end', function () { console.log('Data has been drained'); }); // good practice to catch warnings (ie stat failures and other non-blocking errors) archive.on('warning', function (err) { if (err.code === 'ENOENT') { // log warning } else { // throw error throw err; } }); // good practice to catch this error explicitly archive.on('error', function (err) { throw err; }); const metadata = { contentType: "application/zip", }; archive.pipe(output); // append a file from string archive.append(utilText, { name: tempFilePath }); archive.finalize(); console.log("tempFilePath: " + tempFilePath); console.log("Export Util CSV finished"); } catch (err) { console.log(err); } }