Best way to handle long running tasks

[Ahmet Faruk Acar]

Hi everyone,

We built a web application where we utilized firebase functions for lightweight works such as login, update profile etc.

and we deployed two functions to App Engine. 

Function 1: Downloading an audio/video file from firebase storage and converting it with ffmpeg and uploading converted version back to storage. 

But App Engine is terminating with a signal in the middle of download process (after ~40 seconds) if the file is larger (>500MB)

Function 2: Calling Google API (ASR) and waiting response (progress %) and writing this response to firestore until it's completed (100%).

This process may take between 1 min - 20 min depending on the file length. But here we get two different problems.

1. Either App Engine creates a new instance in the middle of API call process and kills current instance (since we set instances# to 1) even there is no concurrent requests.

I don't understand this behavior since this should not require intensive CPU or memory usage. App Engine gives following Info in logs:

This request caused a new process to be started for your application, and thus caused your application code to be loaded for the first time. This request may thus take longer and use more CPU than a typical request for your application

2. Or App Engine terminates due to idle_timeout even it is waiting async API response and writing it to db. 

It looks like when there is no incoming requests, App Engine is considering itself as idle and terminating after a while (~10 minutes)

Eventhough documentation says:

We are new to GCP and App Engine, so maybe we are using wrong product (e.g. Compute Engine?) 

and we saw PubSub, Cloud Tasks etc. which looks like a solution for our case.

Thus I wonder what could be most elegant way to approach the problem and implement solution?

Any comment, feedback is appreciated.

Regards

A. Faruk Acar

App Engine app.yaml Configuration

runtime: nodejs10

manual_scaling:

    instances: 1

[David (Cloud Platform Support)]

When using AppEngine, it is better to use Cloud Tasks at the moment of performing long-running requests. As you mentioned, you could also use Compute Engine and there could be ways to integrate PubSub but if you are already in App Engine and you would like to stick to it, Cloud Tasks would be a good solution for you.

[Konrad Garus]

I believe Cloud Tasks have a 10-minute timeout, correct?

If you need something longer, with Cloud Tasks you have to go for manual scaling - and give up on the fully managed, "just works" solution.

śr., 8 sty 2020 o 21:45 'David (Cloud Platform Support)' via Google App Engine <google-a...@googlegroups.com> napisał(a):

When using AppEngine, it is better to use Cloud Tasks at the moment of performing long-running requests. As you mentioned, you could also use Compute Engine and there could be ways to integrate PubSub but if you are already in App Engine and you would like to stick to it, Cloud Tasks would be a good solution for you.

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Konrad Garus

[Olu]

the Default Timeouts that apply with Cloud Tasks actually depends on the scaling type of the service. As explained in this documentation[1-- even though the documentation points to App Engine tasks, the same applies with Cloud Tasks], 10 minutes default timeout applies for Automatic scaling standard apps in App Engine Standard environment. You can find more information about the default timeouts and deadlines on this PHP Client Library[2 -- See the section about the dispatch_deadline].

Cloud Tasks enables serverless execution of tasks via App Engine standard or flexible environments

[1]https://cloud.google.com/tasks/docs/creating-appengine-handlers#timeouts

[2]https://googleapis.github.io/google-cloud-php/#/docs/google-cloud/v0.104.0/tasks/v2beta3/task