Get Firebase storage Object on a database-triggered cloud function - firebase

Question

I want to generate a thumb image when a record is added to the database.
On the Firebase website they have some examples but they are all based on a storage trigger instead of a database trigger:
Image database object:
image: {
name: abc123,
raw: download url abc123
}
-
firebase thumb generator example (storage triggered):
exports.generateThumbnail = functions.storage.object().onChange(event => {
const object = event.data; // The Storage object.
const fileBucket = object.bucket; // The Storage bucket that contains the file.
const filePath = object.name; // File path in the bucket.
const contentType = object.contentType; // File content type.
const resourceState = object.resourceState; // The resourceState is 'exists' or 'not_exists' (for file/folder deletions).
const metageneration = object.metageneration; // Number of times metadata has been generated. New objects have a value of 1.
// Exit if this is triggered on a file that is not an image.
if (!contentType.startsWith('image/')) {
console.log('This is not an image.');
return;
}
// Get the file name.
const fileName = path.basename(filePath);
// Exit if the image is already a thumbnail.
if (fileName.startsWith('thumb_')) {
console.log('Already a Thumbnail.');
return;
}
// Exit if this is a move or deletion event.
if (resourceState === 'not_exists') {
console.log('This is a deletion event.');
return;
}
// Exit if file exists but is not new and is only being triggered
// because of a metadata change.
if (resourceState === 'exists' && metageneration > 1) {
console.log('This is a metadata change event.');
return;
}
// Download file from bucket.
const bucket = gcs.bucket(fileBucket);
const metadata = {
contentType: contentType
};
// We add a 'thumb_' prefix to thumbnails file name. That's where we'll upload the thumbnail.
const thumbFileName = `thumb_${fileName}`;
const thumbFilePath = path.join(path.dirname(filePath), thumbFileName);
// Create write stream for uploading thumbnail
const thumbnailUploadStream = bucket.file(thumbFilePath).createWriteStream({metadata});
// Create Sharp pipeline for resizing the image and use pipe to read from bucket read stream
const pipeline = sharp();
pipeline
.resize(THUMB_MAX_WIDTH, THUMB_MAX_HEIGHT)
.max()
.pipe(thumbnailUploadStream);
bucket.file(filePath).createReadStream().pipe(pipeline);
const streamAsPromise = new Promise((resolve, reject) =>
thumbnailUploadStream.on('finish', resolve).on('error', reject));
return streamAsPromise.then(() => {
console.log('Thumbnail created successfully');
});
});
-
How I want it to work (database triggered):
The database trigger event does not have a storage object. How can I access the storage object?
When a thumbnail is created successfully I want to add the donwloadUrl of the thumb image to the database
exports.generateThumbnail = functions.database.ref('/data/{dataID}/childData/{childDataID}/image/name').onCreate(event => {
const object = event.data; // This Storage object does not work when using a database trigger so how do I access the same storage object, I have the image name?
//thumb generator code...
return streamAsPromise.then(() => {
console.log('Thumbnail created successfully');
//add thumb image download url back to the database
});
});
-
image: {
name: abc123,
raw: download url abc123
thumb: download url thumb_abc123 //added after thumb is created
}

Answer 1

This is how I got it to work.
Add cloud storage to your project.
If you want to retrieve the image signed url like I do, add projectId and keyFilename to you cloud storage reference
const gcs = require('#google-cloud/storage')({
projectId: 'name-1234',
keyFilename: './keyfile.json'
});
generateThumbnail function
exports.generateThumbnail = functions.database.ref('/data/${dataID}/childData/${childDataID/image/name').onCreate(image => {
const dataID = image.params.dataID
const childDataID = image.params.childDataID
const fileName = image.data.val()
//get your project storage bucket id
const storageBucket = functions.config().firebase.storageBucket
//path to image
const imagePath = `${dataID}/${childDataID}`
//open bucket
const bucket = gcs.bucket(storageBucket)
//location of the image in the bucket
const object = bucket.file(imagePath)
const fileBucket = object.bucket; // The Storage bucket that contains the file.
const filePath = object.name; // File path in the bucket.
const metadata = {
contentType: 'image/jpeg'
};
// We add a 'thumb_' prefix to thumbnails file name. That's where we'll upload the thumbnail.
const thumbFileName = `thumb_${fileName}`;
const thumbFilePath = path.join(path.dirname(filePath), thumbFileName);
// Create write stream for uploading thumbnail
const thumbnailUploadStream = bucket.file(thumbFilePath).createWriteStream({metadata});
// Create Sharp pipeline for resizing the image and use pipe to read from bucket read stream
const pipeline = sharp();
pipeline
.resize(400, 400)
.max()
.pipe(thumbnailUploadStream);
bucket.file(filePath).createReadStream().pipe(pipeline);
const streamAsPromise = new Promise((resolve, reject) =>
thumbnailUploadStream.on('finish', resolve).on('error', reject));
return streamAsPromise.then(() => {
console.log('Thumbnail created successfully');
var today = new Date();
var dd = today.getDate();
var mm = today.getMonth() + 1; //January is 0!
const yyyy = today.getFullYear() + 5; // add a few years
if (dd < 10) {
dd = '0' + dd
}
if (mm < 10) {
mm = '0' + mm
}
today = mm + '-' + dd + '-' + yyyy;
bucket.file(filePath).getSignedUrl({
action: 'read',
expires: today
}, function(err, url) {
if (err) {
console.error(err);
return;
}
//add thumb image url to message (in database)
return admin.database().ref(`/${dataID}/childData/${childDataID}`).child('image').update({
thumb: url
})
});
});
})