I am trying to create an app that simulates opening a tab at a bar. I am running into one issue that I can't seem to figure out - it goes as follows:
When someone opens a bar tab, dynamically create a scheduled task that executes code to close the tab after 24 hours.
If the tab gets closed before the 24 hours, cancel the scheduled task.
If the tab doesn't get closed after 24 hours, execute the code described in step 1 to initiate a payment on the card used to open the tab.
I was initially looking into Firebase Functions, and was thinking about using a setTimeout() callable function, but after doing some research I found that Firebase Function's cannot be invoked for longer than 9 minutes.
NOTE: I would like this to be dynamic. Meaning, having it account for a variable amount of users. There could be 100 or 1000 users on the platform, each of them needs the ability to have a unique scheduled task for them (sometimes multiple per user).
Please see the comments for the full solution.
There are multiple approaches to circumvent the 10 minutes rule (which is prevalent in the serverless code) but here's something that can help you. I suggest separating the task into three:
A cloud function that close the tab when called.
A schedule function that calls it (https://firebase.google.com/docs/functions/schedule-functions)
A way to start and stop the schedule function.
I am not sure how firebase function work, but I worked with azure functions before and those can be controlled with command line (CLI) or with a sdk for your language of choice. To cancel using the command line, try something like this:
firebase functions:delete scheduledFunction
from How to cancel a scheduled firebase function?.
Now what's left is how to figure out how to start the function, and if it's possible to pass in a parameter to schedule it.
Good luck!
Related
I am using the firebase Stripe API, and what is happening is my app doesn't have a lot of traffic yet, nor will it for a little while. Firebase decided, after 2-3 minutes of no invocations on the function, it goes into cold start mode. This is unfortunate because it means my wait time from when a new user hits register, and goes to the checkout page, it is like 8 seconds. How horrendous is that!
Anyways, does anyone know a way around this, maybe setting a script to run in the background at all times, or something I can do from inside firebase?
One way to help is to add a "cold-start" command to the Cloud Function (i.e. a "no-op" invocation/call), and invoke it when your user starts the checkout process (before collecting any information). If the User doesn't complete check-out, no-harm-no-foul; if they do, the cloud function has already been started.
Update 2020-01-01:
Firebase now allows you to designate for each function, in the console, a minimum (and/or maximum) number of invocations - i.e. keeping functions in memory. A single active function costs about $0.33 to $0.50 per month - a fairly low (but not zero) cost for keeping cold starts down...
I would like to create a firebase cloud function that updates the current second on the real time database, every second.
As far as I understand I am not able to use setInterval because the function will stop after x seconds anyway.
Does anyone have an idea how I can achieve that using cloud functions?
There is no built-in interval based trigger in Cloud Functions for Firebase.
You can build cron-style triggering using other Google services, such as App Engine Cron (as shown in this blog post) or an external web service (as shown in this video).
But neither of those seems particularly well suited for triggering every second. For that kind of constant load, I'd consider spinning up a Node.js process that simply uses setTimeout() or setInterval().
Is there a way to automate functions and call them at a specific mooment in time with Node.Js ? More precisely, I would like to create a reminder with node js. When I receive the date from the user, I have to send notification to remind him/her of something.
I know setTimeout() function but is it really good idea when I have large database of users ?
Thank you.
You can use setTimeout() and keep all the work inside your server, but for a large number of users, you would not necessarily want to set a timeout for every single user. All you really need is a single timeout for the next user that needs to be notified. When that timer fires, you then set a timer for the next user that needs to be notified and so on.
This can be done with an array of objects that you sort by the notification time. Each time you add something to the array, you cancel your current timer, add the new notification to the array, sort the array and set a timer for the earliest notification.
When a timer fires, you remove that item from the array and schedule the next one.
And, since you likely want this to survive a server restart, you save the notification array (probably in JSON format) to a file or to a database each time you modify it so you can reload that data upon a server restart.
FYI, there are scheduling modules for node.js that already offer this type of functionality if you'd prefer to pick up code someone else has already written.
Examples of some of these modules:
node-cron
agenda
node-schedule
What you are looking for is called a Scheduler or a cron job (its origin is from Linux OS).
In NodeJS you can find the node-schedule that implement the same idea.
I am creating a script to collect specific datas from Gmail to Google SpreadSheet. Because there are too many mails the execution time is over 6 minutes so i want to use triggers to automaticaly run the script every 6 minutes. My idea is too use Script Properties to store the ID of the last appended thread in order to get it back at the next script execution and keep gathering datas from other threads.
The problem is: when i manualy start the script the Properties are well updated but when the Trigger does it the Properties are not updated. Do you have any explanations ?
Well, never mind, i have found the problem, so for any one having the same one:
Don't try to test your script with an ui.alert when using a Trigger, it was firring an error and prevented the correct execution of the instructions after that.
My app's framework is built around collapsing backbone models sending the data via websockets and updating models on other clients with the data. My question is how should I batch these updates for times when an action triggers 5 changes in a row.
The syncing method is set up to update on any change but if I set 5 items at the same time I don't want it to fire 5 times in a row.
I was thinking I could do a setTimeout on any sync that gets cleared if something else tries to sync within a second of it. Does this seem like the best route or is there a better way to do this?
Thanks!
i haven't done this with backbone specifically, but i've done this kind of batching of commands in other distributed (client / server) apps in the past.
the gist of it is that you should start with a timeout and add a batch size for further optimization, if you see the need.
say you have a batch size of 10. what happens when you get 9 items stuffed into the batch and then the user just sits there and doesn't do anything else? the server would never get notified of the things the user wanted to do.
timeout generally works well to get small batches. but if you have an action that generates a large number of related commands you may want to batch all of the commands and send them all across as soon as they are ready instead of waiting for a timer. the time may fire in the middle of creating the commands and split things apart in a manner that causes problems, etc.
hope that helps.
Underscore.js, the utility library that Backbone.js uses, has several functions for throttling callbacks:
throttle makes a version of a function that will execute at most once every X milliseconds.
debounce makes a version of a function that will only execute if X milliseconds elapse since the last time it was called
after makes a version of a function that will execute only after it has been called X times.
So if you know there are 5 items that will be changed, you could register a callback like this:
// only call callback after 5 change events
collection.on("change", _.after(5, callback));
But more likely you don't, and you'll want to go with a timeout approach:
// only call callback 30 milliseconds after the last change event
collection.on("change", _.debounce(30, callback));