Refactor Docker networking and health checks in docker-compose.yml

src/go-postgres/.devcontainer/docker-compose.yml

@@ -18,17 +18,44 @@ services:
     # Overrides default command so things don't shut down after the process ends.
     command: sleep infinity
 
-    # Runs app on the same network as the database container, allows "forwardPorts" in devcontainer.json function.
-    network_mode: service:db
+    # Database connection string for Rails applications
+    # Provides a standard way to connect to the PostgreSQL database
+    environment:
+      DATABASE_URL: "postgresql://postgres:postgres@db:5432/postgres"
+
+   # Use proper Docker networking (not network_mode) to avoid namespace issues and ensure reliable container startup across environments
+    depends_on:
+      db:
+        condition: service_healthy # Wait for PostgreSQL to be ready before starting the app
+    networks:
+      - app-network # Connect to custom bridge network for service communication
 
     # Use "forwardPorts" in **devcontainer.json** to forward an app port locally. 
     # (Adding the "ports" property to this file will not forward from a Codespace.)
 
   db:
     image: postgres:latest
     restart: unless-stopped
+    networks:
+      - app-network # Connect to the same network as the app container
+
+    # Health check ensures PostgreSQL is ready before dependent services start
+    # This is critical for depends_on with condition: service_healthy to work properly
+    healthcheck:
+      test: [ "CMD-SHELL", "pg_isready -U postgres" ]
+      interval: 10s # Check every 10 seconds
+      timeout: 5s # Wait up to 5 seconds for response
+      retries: 5 # Retry 5 times before marking as unhealthy
+      start_period: 30s # Give PostgreSQL 30 seconds to start before health checks begin
+
     volumes:
-      - postgres-data:/var/lib/postgresql/data
+      - postgres-data:/var/lib/postgresql/
+    # Custom bridge network for service communication  
+    # Replaces the problematic network_mode: service:db approach
+    networks:
+      app-network:
+        driver: bridge # Standard bridge driver for container-to-container communication
+    # Services on this network can communicate using service names (app -> db)
     env_file:
       # Ensure that the variables in .env match the same variables in devcontainer.json
       - .env