Fix port binding issue by adding dynamic port selection

app/core/config.py

@@ -1,3 +1,4 @@
+import os
 from pathlib import Path
 
 from pydantic_settings import BaseSettings, SettingsConfigDict
@@ -10,9 +11,14 @@ class Settings(BaseSettings):
         extra="ignore"
     )
     
+    # API settings
     API_V1_STR: str = "/api/v1"
     PROJECT_NAME: str = "Todo Application"
     
+    # Server settings
+    HOST: str = "0.0.0.0"  # Listen on all available interfaces
+    PORT: int = 8000  # Default port
+    
     # Database settings
     DB_DIR: Path = Path("/app") / "storage" / "db"
     SQLALCHEMY_DATABASE_URL: str = f"sqlite:///{DB_DIR}/db.sqlite"
@@ -21,5 +27,13 @@ class Settings(BaseSettings):
         super().__init__(**data)
         self.DB_DIR.mkdir(parents=True, exist_ok=True)
         
+        # Override settings from environment variables if they exist
+        if "PORT" in os.environ:
+            try:
+                self.PORT = int(os.environ["PORT"])
+            except ValueError:
+                # If PORT env var isn't a valid int, keep the default
+                pass
+
 
 settings = Settings()

main.py

@@ -1,9 +1,17 @@
+import logging
+import socket
+import sys
+
 import uvicorn
 from fastapi import FastAPI
 
 from app.api.api import api_router
 from app.core.config import settings
 
+# Configure logging
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger(__name__)
+
 app = FastAPI(
     title=settings.PROJECT_NAME,
     openapi_url=f"{settings.API_V1_STR}/openapi.json",
@@ -13,5 +21,44 @@ app = FastAPI(
 
 app.include_router(api_router, prefix=settings.API_V1_STR)
 
+def find_available_port(start_port, max_attempts=10):
+    """Try to find an available port starting from start_port"""
+    for port in range(start_port, start_port + max_attempts):
+        try:
+            # Try to create a socket with the port
+            with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+                s.bind((settings.HOST, port))
+                # If we get here, the port is available
+                return port
+        except OSError:
+            # Port is already in use, try the next one
+            continue
+    
+    # If we get here, no ports were available in our range
+    port_range_end = start_port + max_attempts - 1
+    logger.warning(
+        f"Could not find an available port in range {start_port}-{port_range_end}"
+    )
+    return None
+
 if __name__ == "__main__":
-    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)
+    port = settings.PORT
+    
+    # Check if the port is already in use
+    try:
+        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+            s.bind((settings.HOST, port))
+    except OSError:
+        logger.warning(
+            f"Port {port} is already in use. Trying to find an available port..."
+        )
+        port = find_available_port(port + 1)
+        
+        if port is None:
+            logger.error("Could not find an available port. Exiting.")
+            sys.exit(1)
+        
+        logger.info(f"Using alternative port: {port}")
+    
+    # Start the server with the available port
+    uvicorn.run("main:app", host=settings.HOST, port=port, reload=True)