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Troubleshooting Docker and Kubernetes Containers

Handling Library and Package Errors in a Docker Compose File

Explore how to identify and resolve library and package installation problems in Docker Compose files by working through practical examples with Python, Promtail logging, and Nginx services. Learn to check logs, adjust volume paths, add necessary packages, and configure service commands to ensure successful builds and running containers.

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Overview of package and library installation issues in Docker Compose files

There are scenarios where we try to install some services and get package or library issues. The reasons can include not installing the necessary package for our application properly or not implementing it properly. In most cases, these packages or libraries are needed for the proper running of our application. We’ll be examining, troubleshooting, and resolving some library and package challenges regarding Docker service builds in a Docker Compose file below.

Python application with Promtail logging service

Our first case study is a Python application, that makes use of Promtail as its logging tool. The files we’ll be working with are the docker-compose.yaml, app.py, and promtail-config.yaml files. They’ll be used to build the Python web service and Promtail logging service. They’re all listed below.

  • The docker-compose.yaml file:

YAML
version: '3.8'
services:
  promtail:
    image: python:3.8
    command: >
      sh -c "apt-get update && apt-get install -y && \
      unzip promtail-linux-amd64.zip -d /usr/local/bin && \
      chmod a+x /usr/local/bin/promtail && \
      rm promtail-linux-amd64.zip && \
      promtail -config.file=/etc/promtail/promtail-config.yaml -client.url=docker-desktop:3100"
    volumes:
      - ./promtail-config.yaml:/etc/promtail/promtail-config.yaml:ro
    depends_on:
      - web
  web:
    image: python:3.8
    command: sh -c "pip install flask && python /app/app.py"
    ports:
      - "5000:5000"

  • The app.py file:

Python
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello():
    return 'Hello, world!'
if __name__ == '__main__':
    app.run(host='0.0.0.0', port=80)
    ...