Concurrency and scaling in GCP - Commands & Configuration

Introduction

When many users try to use your app at the same time, it can slow down or crash. Concurrency and scaling help your app handle many users smoothly by running multiple tasks at once and adding more resources automatically.

When your website gets more visitors than usual and you want it to stay fast.

When your app needs to process many requests at the same time without waiting.

When you want your service to add more servers automatically during busy times.

When you want to save money by using fewer resources when traffic is low.

When you want to avoid crashes caused by too many users accessing your app.

Config File - app.yaml

app.yaml

runtime: python39
instance_class: F2
automatic_scaling:
  target_cpu_utilization: 0.65
  min_instances: 1
  max_instances: 5
  max_concurrent_requests: 50

This file configures an App Engine service on Google Cloud.

runtime sets the Python version.

instance_class chooses the server size.

automatic_scaling controls how the app adds or removes instances based on CPU use and request load.

max_concurrent_requests limits how many requests one instance handles at once to balance speed and resource use.

Commands

This command uploads and applies the configuration to Google App Engine, starting your app with the scaling settings.

Terminal

gcloud app deploy app.yaml

Expected Output

Services to deploy:

  descriptor: app.yaml



Beginning deployment...

Updating service [default]...

Waiting for operation to complete...



Deployed service [default] to [https://PROJECT_ID.uc.r.appspot.com]



You can stream logs from the command line by running:

  gcloud app logs tail -s default

This command shows the current running instances of your app, so you can see how many servers are active.

Terminal

gcloud app instances list

Expected Output

SERVICE  VERSION  INSTANCE  VM_ID                                   VM_IP           STATE

default  20240601  instance-1  1234567890abcdef1234567890abcdef  35.233.123.45   RUNNING

This command streams live logs from your app to watch how it handles requests and scales in real time.

Terminal

gcloud app logs tail -s default

Expected Output

2024-06-01 12:00:00 default[20240601]: Started request GET / from 203.0.113.1

2024-06-01 12:00:01 default[20240601]: Completed request GET / with status 200

→

-s - Specifies the service to get logs from

Key Concept

If you remember nothing else from this pattern, remember: scaling automatically adds or removes app instances based on demand to keep your app fast and stable.

Common Mistakes

Setting max_instances too low

Your app cannot add enough servers during high traffic, causing slow responses or errors.

Set max_instances high enough to handle peak traffic safely.

Not limiting max_concurrent_requests

One instance tries to handle too many requests at once, leading to slow processing or crashes.

Set max_concurrent_requests to a reasonable number to balance load per instance.

Forgetting to deploy after changing app.yaml

Your scaling settings do not update, so the app does not scale as expected.

Always run 'gcloud app deploy app.yaml' after editing the config file.

Summary

Create an app.yaml file to set automatic scaling rules for your app.

Deploy the app with 'gcloud app deploy app.yaml' to apply scaling settings.

Use 'gcloud app instances list' to check how many app instances are running.

Stream logs with 'gcloud app logs tail -s default' to monitor app behavior and scaling.