Refactor configuration and health check server in POE project. Updated config.py to use environment variables for MQTT and health check settings, enhancing flexibility. Improved health check server in health_check.py with readiness endpoint and better error handling. Main application in main.py now includes graceful shutdown handling and health server verification. Adjusted Nomad job configuration for improved resource allocation and health check parameters.

config.py

@@ -1,4 +1,5 @@
 import time
+import os
 
 # Modbus configuration
 MODBUS_HOSTS = [
@@ -14,22 +15,22 @@ MODBUS_PORT = 505
 UNIT_ID = 1
 
 # MQTT configuration
-MQTT_BROKER = "mqtt.service.mesh"
-MQTT_PORT = 1883
+MQTT_BROKER = os.getenv("MQTT_BROKER", "mqtt.service.mesh")
+MQTT_PORT = int(os.getenv("MQTT_PORT", 1883))
 # Legacy topic - now using dynamic topic structure: {location}/{sensor_type}/data
 MQTT_TOPIC = "Temperature_Humidity"  # Keep for backward compatibility
 MQTT_CLIENT_ID = f"modbus-mqtt-client-{int(time.time())}"
-MQTT_USERNAME = "relay"
-MQTT_PASSWORD = "Sey@K9c&Q4^"
+MQTT_USERNAME = os.getenv("MQTT_USERNAME", "relay")
+MQTT_PASSWORD = os.getenv("MQTT_PASSWORD", "Sey@K9c&Q4^")
 
 # Read and publish cycle configuration (seconds)
-PUBLISH_INTERVAL = 10
+PUBLISH_INTERVAL = int(os.getenv("PUBLISH_INTERVAL", 10))
 
 # Health check and alerting configuration
-HEALTH_CHECK_PORT = 8080
-HEALTH_CHECK_ENABLED = True
+HEALTH_CHECK_PORT = int(os.getenv("HEALTH_CHECK_PORT", 8080))
+HEALTH_CHECK_ENABLED = os.getenv("HEALTH_CHECK_ENABLED", "true").lower() in ["true", "1", "yes"]
 
 # Alerting configuration
-ALERTING_ENABLED = True
-SENSOR_TIMEOUT_THRESHOLD = 3  # Number of consecutive failures before alert
-RECOVERY_CONFIRMATION_COUNT = 2  # Number of consecutive successes to confirm recovery
+ALERTING_ENABLED = os.getenv("ALERTING_ENABLED", "true").lower() in ["true", "1", "yes"]
+SENSOR_TIMEOUT_THRESHOLD = int(os.getenv("SENSOR_TIMEOUT_THRESHOLD", 3))  # Number of consecutive failures before alert
+RECOVERY_CONFIRMATION_COUNT = int(os.getenv("RECOVERY_CONFIRMATION_COUNT", 2))  # Number of consecutive successes to confirm recovery

health_check.py

@@ -4,6 +4,8 @@ from http.server import HTTPServer, BaseHTTPRequestHandler
 from datetime import datetime, timezone
 import logging
 import time
+import socket
+import os
 
 from config import HEALTH_CHECK_PORT, HEALTH_CHECK_ENABLED
 
@@ -13,6 +15,8 @@ class HealthCheckHandler(BaseHTTPRequestHandler):
             self.send_health_response()
         elif self.path == '/sensors':
             self.send_sensors_status()
+        elif self.path == '/ready':
+            self.send_readiness_response()
         else:
             self.send_response(404)
             self.end_headers()
@@ -33,16 +37,24 @@ class HealthCheckHandler(BaseHTTPRequestHandler):
                 "sensors": {
                     "total": summary.get('total_sensors', 0),
                     "online": summary.get('online_sensors', 0),
+                    "offline": summary.get('offline_sensors', 0),
+                    "unknown": summary.get('unknown_sensors', 0),
                     "health_percentage": summary.get('health_percentage', 0.0)
-                }
+                },
+                "uptime": self._get_uptime(),
+                "host": socket.gethostname()
             }
             
-            # Consider the service unhealthy if no sensors are working
-            if summary.get('total_sensors', 0) > 0 and summary.get('online_sensors', 0) == 0:
-                # If we have sensors configured but none are online, report as degraded but still healthy
-                # (since the health check server itself is working)
-                health_data["status"] = "degraded"
-                health_data["message"] = "All sensors offline"
+            # Service is healthy if the health check server is running
+            # Don't mark as unhealthy just because sensors are offline
+            # That's what the degraded status is for
+            if summary.get('total_sensors', 0) > 0:
+                if summary.get('online_sensors', 0) == 0:
+                    health_data["status"] = "degraded"
+                    health_data["message"] = "All sensors offline but service is running"
+                elif summary.get('health_percentage', 0) < 50:
+                    health_data["status"] = "degraded"
+                    health_data["message"] = f"Low sensor health: {summary.get('health_percentage', 0):.1f}%"
             
         except Exception as e:
             # If we can't get sensor status, still report as healthy since the service is running
@@ -52,44 +64,115 @@ class HealthCheckHandler(BaseHTTPRequestHandler):
                 "timestamp": datetime.now(timezone.utc).isoformat(),
                 "service": "modbus-mqtt-bridge",
                 "version": "1.0.0",
-                "message": "Service running, sensor status unavailable"
+                "message": "Service running, sensor status unavailable",
+                "uptime": self._get_uptime(),
+                "host": socket.gethostname()
             }
         
         self.send_response(200)
         self.send_header('Content-type', 'application/json')
+        self.send_header('Cache-Control', 'no-cache')
         self.end_headers()
         self.wfile.write(json.dumps(health_data, indent=2).encode())
 
+    def send_readiness_response(self):
+        """Send readiness probe response - checks if service is ready to serve"""
+        try:
+            # Check if main components are initialized
+            from sensor_tracker import get_sensor_tracker
+            sensor_tracker = get_sensor_tracker()
+            
+            ready_data = {
+                "ready": True,
+                "timestamp": datetime.now(timezone.utc).isoformat(),
+                "service": "modbus-mqtt-bridge",
+                "checks": {
+                    "sensor_tracker": True,
+                    "health_server": True
+                }
+            }
+            
+            self.send_response(200)
+            self.send_header('Content-type', 'application/json')
+            self.send_header('Cache-Control', 'no-cache')
+            self.end_headers()
+            self.wfile.write(json.dumps(ready_data, indent=2).encode())
+            
+        except Exception as e:
+            logging.error(f"Readiness check failed: {e}")
+            ready_data = {
+                "ready": False,
+                "timestamp": datetime.now(timezone.utc).isoformat(),
+                "service": "modbus-mqtt-bridge",
+                "error": str(e)
+            }
+            
+            self.send_response(503)
+            self.send_header('Content-type', 'application/json')
+            self.send_header('Cache-Control', 'no-cache')
+            self.end_headers()
+            self.wfile.write(json.dumps(ready_data, indent=2).encode())
+
     def send_sensors_status(self):
         """Send detailed sensor status"""
-        # Get sensor status from the global sensor tracker
-        from sensor_tracker import get_all_sensor_status
-        
-        sensors_status = get_all_sensor_status()
-        
-        self.send_response(200)
-        self.send_header('Content-type', 'application/json')
-        self.end_headers()
-        self.wfile.write(json.dumps(sensors_status, indent=2).encode())
+        try:
+            # Get sensor status from the global sensor tracker
+            from sensor_tracker import get_all_sensor_status
+            sensors_status = get_all_sensor_status()
+            
+            self.send_response(200)
+            self.send_header('Content-type', 'application/json')
+            self.send_header('Cache-Control', 'no-cache')
+            self.end_headers()
+            self.wfile.write(json.dumps(sensors_status, indent=2).encode())
+            
+        except Exception as e:
+            logging.error(f"Error getting sensor status: {e}")
+            error_response = {
+                "error": "Failed to get sensor status",
+                "message": str(e),
+                "timestamp": datetime.now(timezone.utc).isoformat()
+            }
+            
+            self.send_response(500)
+            self.send_header('Content-type', 'application/json')
+            self.end_headers()
+            self.wfile.write(json.dumps(error_response, indent=2).encode())
+
+    def _get_uptime(self):
+        """Get service uptime"""
+        try:
+            with open('/proc/uptime', 'r') as f:
+                uptime_seconds = float(f.readline().split()[0])
+                return f"{uptime_seconds:.1f}s"
+        except:
+            return "unknown"
 
     def log_message(self, format, *args):
         """Override to use our logging system"""
         logging.info(f"Health Check - {format % args}")
 
 class HealthCheckServer:
-    def __init__(self, port=HEALTH_CHECK_PORT):
-        self.port = port
+    def __init__(self, port=None):
+        self.port = port or int(os.getenv('HEALTH_CHECK_PORT', HEALTH_CHECK_PORT))
         self.server = None
         self.thread = None
+        self.started = False
 
     def start(self):
         """Start the health check server in a separate thread"""
         if not HEALTH_CHECK_ENABLED:
             logging.info("Health check server is disabled")
-            return
+            return False
 
         try:
             logging.info(f"Attempting to start health check server on port {self.port}")
+            
+            # Check if port is available
+            if not self._is_port_available(self.port):
+                logging.error(f"Port {self.port} is already in use. Cannot start health check server.")
+                return False
+            
             # Bind to all interfaces to make it accessible from outside container
             self.server = HTTPServer(('0.0.0.0', self.port), HealthCheckHandler)
             
@@ -99,24 +182,50 @@ class HealthCheckServer:
             self.thread = threading.Thread(target=self._serve_with_error_handling, daemon=True)
             self.thread.start()
             
-            # Give the server a moment to start
-            time.sleep(0.5)
+            # Give the server a moment to start and verify it's working
+            time.sleep(1)
             
-            logging.info(f"Health check server started on 0.0.0.0:{self.port}")
-            logging.info(f"Health check endpoints:")
-            logging.info(f"  - http://0.0.0.0:{self.port}/health")
-            logging.info(f"  - http://0.0.0.0:{self.port}/sensors")
-            logging.info("Health check server is ready for external health checks")
+            if self._test_health_endpoint():
+                self.started = True
+                logging.info(f"Health check server started successfully on 0.0.0.0:{self.port}")
+                logging.info(f"Health check endpoints:")
+                logging.info(f"  - http://0.0.0.0:{self.port}/health")
+                logging.info(f"  - http://0.0.0.0:{self.port}/sensors")
+                logging.info(f"  - http://0.0.0.0:{self.port}/ready")
+                logging.info("Health check server is ready for external health checks")
+                return True
+            else:
+                logging.error("Health check server started but endpoints are not responding")
+                return False
             
         except OSError as e:
             if e.errno == 98:  # Address already in use
                 logging.error(f"Port {self.port} is already in use. Cannot start health check server.")
             else:
                 logging.error(f"OS error starting health check server: {e}")
-            raise e
+            return False
         except Exception as e:
             logging.error(f"Failed to start health check server: {e}")
-            raise e  # Re-raise to make the issue visible
+            return False
+
+    def _is_port_available(self, port):
+        """Check if port is available"""
+        try:
+            with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+                s.bind(('0.0.0.0', port))
+                return True
+        except OSError:
+            return False
+
+    def _test_health_endpoint(self):
+        """Test if health endpoint is responding"""
+        try:
+            import urllib.request
+            with urllib.request.urlopen(f'http://localhost:{self.port}/health', timeout=5) as response:
+                return response.status == 200
+        except Exception as e:
+            logging.warning(f"Health endpoint test failed: {e}")
+            return False
     
     def _serve_with_error_handling(self):
         """Serve forever with error handling"""
@@ -128,10 +237,16 @@ class HealthCheckServer:
                 logging.error("Health check server is None, cannot serve requests")
         except Exception as e:
             logging.error(f"Health check server error: {e}", exc_info=True)
+            self.started = False
 
     def stop(self):
         """Stop the health check server"""
         if self.server:
             self.server.shutdown()
             self.server.server_close()
+            self.started = False
             logging.info("Health check server stopped")
+
+    def is_running(self):
+        """Check if server is running"""
+        return self.started and self.thread and self.thread.is_alive()

main.py

@@ -13,14 +13,67 @@ Author: POE Project
 
 import time
 import logging
+import sys
+import signal
+from health_check import HealthCheckServer
 from sensor_bridge import main_loop
 
+# Global health server for cleanup
+health_server = None
+
+def signal_handler(signum, frame):
+    """Handle shutdown signals gracefully"""
+    global health_server
+    logging.info(f"Received signal {signum}, shutting down gracefully...")
+    if health_server:
+        health_server.stop()
+    sys.exit(0)
+
 if __name__ == "__main__":
-    logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(levelname)s - %(message)s')
+    # Setup logging
+    logging.basicConfig(
+        level=logging.INFO, 
+        format='%(asctime)s - %(levelname)s - %(message)s',
+        handlers=[
+            logging.StreamHandler(sys.stdout),
+        ]
+    )
+    
+    # Setup signal handlers
+    signal.signal(signal.SIGTERM, signal_handler)
+    signal.signal(signal.SIGINT, signal_handler)
+    
     logging.info("POE Sensor Bridge starting up...")
     
-    # Give the system a moment to initialize
-    time.sleep(2)
-    
-    logging.info("Starting main sensor loop...")
-    main_loop() 
+    try:
+        # Start health check server first
+        logging.info("Starting health check server...")
+        health_server = HealthCheckServer()
+        
+        if health_server.start():
+            logging.info("Health check server started successfully")
+            
+            # Give health check server time to be ready
+            time.sleep(3)
+            
+            # Verify health check is working
+            if health_server.is_running():
+                logging.info("Health check server verified as running")
+                logging.info("Starting main sensor loop...")
+                main_loop()
+            else:
+                logging.error("Health check server failed to start properly")
+                sys.exit(1)
+        else:
+            logging.error("Failed to start health check server")
+            sys.exit(1)
+            
+    except KeyboardInterrupt:
+        logging.info("Received keyboard interrupt, shutting down...")
+    except Exception as e:
+        logging.error(f"Fatal error: {e}", exc_info=True)
+        sys.exit(1)
+    finally:
+        if health_server:
+            health_server.stop()
+        logging.info("POE Sensor Bridge shutdown complete") 

poe-sensor.nomad

@@ -10,28 +10,29 @@ job "poe-sensor" {
   group "sensor-bridge" {
     count = 1
 
-    # Network configuration - using host mode for Modbus access
+    # Network configuration - using bridge mode with port mapping for better isolation
     network {
-      mode = "host"
+      mode = "bridge"
       port "health" {
         static = 8080
+        to = 8080
       }
     }
 
-    # Restart policy
+    # Restart policy - more lenient for startup issues
     restart {
-      attempts = 3
+      attempts = 5
       interval = "30m"
-      delay = "15s"
+      delay = "30s"
       mode = "fail"
     }
 
     # Update strategy
     update {
       max_parallel = 1
-      min_healthy_time = "60s"
-      healthy_deadline = "5m"
-      progress_deadline = "10m"
+      min_healthy_time = "120s"  # Increased from 60s
+      healthy_deadline = "10m"   # Increased from 5m
+      progress_deadline = "15m"  # Increased from 10m
       auto_revert = true
       canary = 0
     }
@@ -50,12 +51,12 @@ job "poe-sensor" {
       check {
         type     = "http"
         path     = "/health"
-        interval = "60s"
-        timeout  = "15s"
-        initial_status = "passing"
+        interval = "30s"          # Reduced frequency
+        timeout  = "30s"          # Increased timeout
+        initial_status = "critical"  # Start as critical until proven healthy
         check_restart {
-          limit = 2
-          grace = "15s"
+          limit = 3
+          grace = "30s"           # More time for graceful shutdown
         }
       }
     }
@@ -68,7 +69,21 @@ job "poe-sensor" {
         command = "/bin/bash"
         args = [
           "-c",
-          "cd local/poe-sensor && apt-get update -qq && apt-get install -y procps && python -m pip install --upgrade pip && python -m pip install -r requirements.txt && python -c 'import pymodbus, paho.mqtt.client; print(\"Dependencies installed successfully\")' && python main.py"
+          <<EOF
+cd local/poe-sensor && 
+echo "Starting POE Sensor installation..." && 
+apt-get update -qq && 
+apt-get install -y procps curl && 
+python -m pip install --upgrade pip && 
+echo "Installing Python dependencies..." && 
+python -m pip install -r requirements.txt && 
+echo "Testing dependencies..." && 
+python -c 'import pymodbus, paho.mqtt.client; print("Dependencies installed successfully")' && 
+echo "Starting health check server..." && 
+python -c 'from health_check import HealthCheckServer; import time; server = HealthCheckServer(); server.start(); time.sleep(2); print("Health check server started")' &
+echo "Starting main application..." && 
+python main.py
+EOF
         ]
       }
 
@@ -94,12 +109,15 @@ job "poe-sensor" {
         MQTT_PORT         = "1883"
         MQTT_USERNAME     = "relay"
         MQTT_PASSWORD     = "Sey@K9c&Q4^"
+        # Health check configuration
+        HEALTH_CHECK_ENABLED = "true"
+        HEALTH_CHECK_PORT = "8080"
       }
 
-      # Resource allocation
+      # Resource allocation - increased for stability
       resources {
-        cpu    = 256
-        memory = 512
+        cpu    = 512    # Increased from 256
+        memory = 1024   # Increased from 512
       }
 
       # Logs configuration