Bits of .NET

🧟 Key Takeaways: Docker init prevents zombie processes in containers. Essential for long-running applications.

Containers can have zombie processes. Docker init fixes this.

❌ The Problem – Zombie Processes

# ❌ Child processes become zombies
# In container without init
PID 1: dotnet MyApp.dll
  PID 10: node script.js (zombie!)
  PID 11: python worker.py (zombie!)
  PID 12: curl download (zombie!)

# 🧟 Zombie processes accumulate over time
# Eventually, container runs out of PID space
# Container must be restarted

✅ The Solution – Docker Init

# ✅ Use docker init in Dockerfile
FROM mcr.microsoft.com/dotnet/aspnet:8.0

# ✅ Install tini for proper init
RUN apt-get update && apt-get install -y tini

# ✅ Use tini as init
ENTRYPOINT ["/usr/bin/tini", "--", "dotnet", "MyApp.dll"]

💡 Docker Compose Init

# docker-compose.yml
version: '3.8'

services:
  app:
    build: .
    # ✅ Use init in compose
    init: true
    # ✅ Or use custom init
    entrypoint: ["/usr/bin/tini", "--", "dotnet", "MyApp.dll"]
    ports:
      - "5000:80"
    
  worker:
    image: myworker:latest
    init: true  # ✅ Zombie protection!
    environment:
      - DOTNET_ENVIRONMENT=Production

💡 Pro Tip: Custom Init Script

# ✅ Custom init script
#!/bin/bash
# init.sh - Reaps zombie processes

# Start main application
dotnet MyApp.dll &

# Reaper loop
while true; do
    # Reap zombie processes
    wait -n || true
    sleep 1
done