Delete firebase data older than 2 hours

Question

I would like to delete data that is older than two hours. Currently, on the client-side, I loop through all the data and run a delete on the outdated data. When I do this, the db.on('value') function is invoked every time something is deleted. Also, things will only be deleted when a client connects, and what might happen if two clients connect at once?

Where can I set up something that deletes old data? I have a timestamp inside each object created by a JavaScript Date.now().

Answer 1

Firebase does not support queries with a dynamic parameter, such as "two hours ago". It can however execute a query for a specific value, such as "after August 14 2015, 7:27:32 AM".

That means that you can run a snippet of code periodically to clean up items that are older than 2 hours at that time:

var ref = firebase.database().ref('/path/to/items/'); var now = Date.now(); var cutoff = now - 2 * 60 * 60 * 1000; var old = ref.orderByChild('timestamp').endAt(cutoff).limitToLast(1); var listener = old.on('child_added', function(snapshot) {     snapshot.ref.remove(); }); 

As you'll note I use child_added instead of value, and I limitToLast(1). As I delete each child, Firebase will fire a child_added for the new "last" item until there are no more items after the cutoff point.

Update: if you want to run this code in Cloud Functions for Firebase:

exports.deleteOldItems = functions.database.ref('/path/to/items/{pushId}') .onWrite((change, context) => {   var ref = change.after.ref.parent; // reference to the items   var now = Date.now();   var cutoff = now - 2 * 60 * 60 * 1000;   var oldItemsQuery = ref.orderByChild('timestamp').endAt(cutoff);   return oldItemsQuery.once('value', function(snapshot) {     // create a map with all children that need to be removed     var updates = {};     snapshot.forEach(function(child) {       updates[child.key] = null     });     // execute all updates in one go and return the result to end the function     return ref.update(updates);   }); }); 

This function triggers whenever data is written under /path/to/items, so child nodes will only be deleted when data is being modified.

This code is now also available in the functions-samples repo.

Answer 2

I have a http triggered cloud function that deletes nodes, depending on when they were created and their expiration date.

When I add a node to the database, it needs two fields: timestamp to know when it was created, and duration to know when the offer must expire.

Then, I have this http triggered cloud function:

const functions = require('firebase-functions'); const admin = require('firebase-admin'); admin.initializeApp();  /**  * @function HTTP trigger that, when triggered by a request, checks every message of the database to delete the expired ones.  * @type {HttpsFunction}  */ exports.removeOldMessages = functions.https.onRequest((req, res) => {     const timeNow = Date.now();     const messagesRef = admin.database().ref('/messages');     messagesRef.once('value', (snapshot) => {         snapshot.forEach((child) => {             if ((Number(child.val()['timestamp']) + Number(child.val()['duration'])) <= timeNow) {                 child.ref.set(null);             }         });     });     return res.status(200).end(); }); 

You can create a cron job that every X minutes makes a request to the URL of that function: https://cron-job.org/en/

But I prefer to run my own script, that makes a request every 10 seconds:

watch -n10 curl -X GET https://(your-zone)-(your-project-id).cloudfunctions.net/removeOldMessages