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Example apps

Flask + Redis HTTP Server

This guide explains how to create and deploy a Flask app with a Redis database on Unikraft Cloud. The example consists of two services: a Flask web server that increments a page view counter stored in Redis.

To run this example, follow these steps:

1. Install the unikraft CLI. You need a BuildKit builder. The easiest way to get one is via Docker. Alternatively, you can also directly set up and use BuildKit, see the quick start.

2. Clone the examples repository and cd into the examples/httpserver-flask-redis directory:

   Code
   git clone https://github.com/unikraft-cloud/examples
   cd examples/httpserver-flask-redis/

Make sure to log into Unikraft Cloud and pick a metro close to you. This guide uses fra (Frankfurt, 🇩🇪):

Code
unikraft login

Deploy Redis

First, deploy the Redis instance. Redis is an internal service (not publicly accessible), reached via the redis.internal domain:

Code
unikraft build redis/ --output <my-org>/redis:latest
unikraft run --metro fra \
  -m 256M \
  --scale-to-zero policy=idle,cooldown-time=1000,stateful=true \
  --domain redis.internal \
  --image <my-org>/redis:latest

The output shows the Redis instance details:

Code
metro:         fra
name:          redis-09p2q
uuid:          0355f93a-7b60-4ade-9359-b01671e812b3
state:         starting
image:         <my-org>/redis
resources:
  memory:      256MiB
  vcpus:       1
service:
  uuid:        19c050b2-b5c9-4e8e-9d25-a9053ff09270
  name:        damp-brook-xmmmwzwo
  domains:
  - fqdn:      redis.internal
networks:
- uuid:        97df34f7-63bc-4f02-a1b4-5ba07278de00
  private-ip:  10.0.0.41
  mac:         12:b0:0a:00:00:29
timestamps:
  created:     just now
scale-to-zero: policy=idle,stateful=true,cooldown-time=1s

Deploy Flask

Next, deploy the Flask web server. It connects to Redis using the REDIS_HOST and REDIS_PORT environment variables:

Code
unikraft build flask/ --output <my-org>/flask:latest
unikraft run --metro fra \
  -m 512M \
  -p 443:8000/tls+http \
  --scale-to-zero policy=on,cooldown-time=1000 \
  --env REDIS_HOST=redis.internal \
  --env REDIS_PORT=6379 \
  --image <my-org>/flask:latest

The output shows the Flask instance details:

Code
metro:          fra
name:           flask-q62qa
uuid:           d081ec92-629b-45b3-8caf-059e0a87dffd
state:          starting
image:          <my-org>/flask
runtime:
  env:
    REDIS_HOST: redis.internal
    REDIS_PORT: 6379
resources:
  memory:       512MiB
  vcpus:        1
service:
  uuid:         ac1cd90e-a1fe-478c-8f58-8598fa80c494
  name:         hidden-silence-htyml3s2
  domains:
  - fqdn:       hidden-silence-htyml3s2.fra.unikraft.app
networks:
- uuid:         d2f3d024-3082-4e98-be22-f36df84263a1
  private-ip:   10.0.0.53
  mac:          12:b0:0a:00:00:35
timestamps:
  created:      just now
scale-to-zero:  policy=on,cooldown-time=1s

In this case, the Flask instance address is https://withered-cherry-xfcrfp93.fra.unikraft.app. It's different for each run.

Test the deployment

Use curl to query the Flask instance. Each request increments the Redis counter:

Code
curl https://withered-cherry-xfcrfp93.fra.unikraft.app

Code
This webpage has been viewed 1 time(s)

Code
curl https://withered-cherry-xfcrfp93.fra.unikraft.app

Code
This webpage has been viewed 2 time(s)

You can list information about the instances by running:

Code
unikraft instances list

Clean up

When done, remove the instances:

Code
unikraft instances delete flask-q62qa
unikraft instances delete redis-09p2q

Learn more

Use the --help option for detailed information on using Unikraft Cloud:

Code
unikraft --help

Or visit the CLI Reference.