Issues with docker application through Azure Pipelines to an Azure App Service (Linux)

[crimson drift]

I am currently trying to set up a multi-container docker application built and deployed using Azure Pipelines to an Azure App Service running Linux.
In this application I have my frontend, backend and postgres database, where I need persistent data for the database.

After trying a lot of different configurations, I've ended up with something like this (obv omitted irrelevant info):

docker-compose.yml

services:
  postgres:
    image: postgres:alpine
    ports:
      - 5432:5432
    volumes:
      - ${WEBAPP_STORAGE_HOME}:/var/lib/postgresql/data/pgdata

  server:
    depends_on:
      - postgres

  client:
    depends_on:
      - server

azure-pipelines.yml

trigger:
- main

pool:
  vmImage: ubuntu-latest

steps:
- task: DockerCompose@0
  displayName: Build services
  inputs:
    containerregistrytype: 'Azure Container Registry'
    dockerComposeFile: '**/docker-compose.yml'
    action: 'Build Services'
- task: DockerCompose@0
  displayName: Push container to container registry
  inputs:
    containerregistrytype: 'Azure Container Registry'
    dockerComposeFile: '**/docker-compose.yml'
    action: 'Push Services'
- task: DockerCompose@0
  displayName: Run services
  inputs:
    containerregistrytype: 'Azure Container Registry'
    dockerComposeFile: '**/docker-compose.yml'
    action: 'Run Services'

During the "Run services" task the build fails with the following error:

[error]The WEBAPP_STORAGE_HOME variable is not set. Defaulting to a blank string.

The Run services task was originally added because without it I ended up with only the frontend part of the application running on the App Service.
I've added WEBSITES_ENABLE_APP_SERVICE_STORAGE = TRUE to my App Service configuration, but that didn't do anything. I suspect this is because the Run Services task is initiated before its pushed to the App Service.

Is there something obvious I am missing here? I've been stuck on this for a while now and I'm not sure what to do next.

[icy jay]

Its probably not what you are looking for. But hosting a Database on a App Service , is not its purpose. In general aside the code, you dont want to have data persistency on WebServers. Why you just dont use the PaaS Postgres DB?

[crimson drift]

The only reason I am trying to jam a database inside the App Service is to reduce cost. The app I am working on is something that is probably being used once a week by a really low number of people. Having looked at the pricing on Azure, running both an App Service and in addition the cheapest PostgreSQL solution seems too much.

[spice drum]

If you are running it very rarely, azure has a sql database that you can price in at 5$ a month. It is primarily meant for development, but can be used in low volume requests in production if you never really intend to scale out.