Persistent polling interval increased. Healthcheck now uses poll instead of separate handshakes.

app/main.py

@@ -92,10 +92,14 @@ async def health():
 
 @app.get("/health/devices")
 async def health_devices():
-    """Enhanced health check that tests device connectivity."""
+    """Enhanced health check that tests device connectivity.
+
+    Uses the connection pool to avoid unnecessary TCP handshakes — if a
+    cached connection exists and is alive, the device is reachable.
+    """
     from sqlalchemy.orm import Session
     from app.database import SessionLocal
-    from app.services import NL43Client
+    from app.services import _connection_pool
     from app.models import NL43Config
 
     db: Session = SessionLocal()
@@ -105,7 +109,7 @@ async def health_devices():
         configs = db.query(NL43Config).filter_by(tcp_enabled=True).all()
 
         for cfg in configs:
-            client = NL43Client(cfg.host, cfg.tcp_port, timeout=2.0, ftp_username=cfg.ftp_username, ftp_password=cfg.ftp_password)
+            device_key = f"{cfg.host}:{cfg.tcp_port}"
             status = {
                 "unit_id": cfg.unit_id,
                 "host": cfg.host,
@@ -115,14 +119,22 @@ async def health_devices():
             }
 
             try:
-                # Try to connect (don't send command to avoid rate limiting issues)
-                import asyncio
-                reader, writer = await asyncio.wait_for(
-                    asyncio.open_connection(cfg.host, cfg.tcp_port), timeout=2.0
-                )
-                writer.close()
-                await writer.wait_closed()
-                status["reachable"] = True
+                # Check if pool already has a live connection (zero-cost check)
+                pool_stats = _connection_pool.get_stats()
+                conn_info = pool_stats["connections"].get(device_key)
+                if conn_info and conn_info["alive"]:
+                    status["reachable"] = True
+                    status["source"] = "pool"
+                else:
+                    # No cached connection — do a lightweight acquire/release
+                    # This opens a connection if needed but keeps it in the pool
+                    import asyncio
+                    reader, writer, from_cache = await _connection_pool.acquire(
+                        device_key, cfg.host, cfg.tcp_port, timeout=2.0
+                    )
+                    await _connection_pool.release(device_key, reader, writer, cfg.host, cfg.tcp_port)
+                    status["reachable"] = True
+                    status["source"] = "cached" if from_cache else "new"
             except Exception as e:
                 status["error"] = str(type(e).__name__)
                 logger.warning(f"Device {cfg.unit_id} health check failed: {e}")

app/routers.py

@@ -1755,74 +1755,38 @@ async def run_diagnostics(unit_id: str, db: Session = Depends(get_db)):
         "message": "TCP communication enabled"
     }
 
-    # Test 3: Modem/Router reachable (check port 443 HTTPS)
+    # Test 3: TCP connection reachable (device port) — uses connection pool
+    # This avoids extra TCP handshakes over cellular. If a cached connection
+    # exists and is alive, we skip the handshake entirely.
+    from app.services import _connection_pool
+    device_key = f"{cfg.host}:{cfg.tcp_port}"
     try:
-        reader, writer = await asyncio.wait_for(
-            asyncio.open_connection(cfg.host, 443), timeout=3.0
-        )
-        writer.close()
-        await writer.wait_closed()
-        diagnostics["tests"]["modem_reachable"] = {
-            "status": "pass",
-            "message": f"Modem/router reachable at {cfg.host}"
-        }
-    except asyncio.TimeoutError:
-        diagnostics["tests"]["modem_reachable"] = {
-            "status": "fail",
-            "message": f"Modem/router timeout at {cfg.host} (network issue)"
-        }
-        diagnostics["overall_status"] = "fail"
-        return diagnostics
-    except ConnectionRefusedError:
-        # Connection refused means host is up but port 443 closed - that's ok
-        diagnostics["tests"]["modem_reachable"] = {
-            "status": "pass",
-            "message": f"Modem/router reachable at {cfg.host} (HTTPS closed)"
-        }
-    except Exception as e:
-        diagnostics["tests"]["modem_reachable"] = {
-            "status": "fail",
-            "message": f"Cannot reach modem/router at {cfg.host}: {str(e)}"
-        }
-        diagnostics["overall_status"] = "fail"
-        return diagnostics
-
-    # Test 4: TCP connection reachable (device port)
-    try:
-        reader, writer = await asyncio.wait_for(
-            asyncio.open_connection(cfg.host, cfg.tcp_port), timeout=3.0
-        )
-        writer.close()
-        await writer.wait_closed()
-        diagnostics["tests"]["tcp_connection"] = {
-            "status": "pass",
-            "message": f"TCP connection successful to {cfg.host}:{cfg.tcp_port}"
-        }
-    except asyncio.TimeoutError:
-        diagnostics["tests"]["tcp_connection"] = {
-            "status": "fail",
-            "message": f"Connection timeout to {cfg.host}:{cfg.tcp_port}"
-        }
-        diagnostics["overall_status"] = "fail"
-        return diagnostics
-    except ConnectionRefusedError:
-        diagnostics["tests"]["tcp_connection"] = {
-            "status": "fail",
-            "message": f"Connection refused by {cfg.host}:{cfg.tcp_port}"
-        }
-        diagnostics["overall_status"] = "fail"
-        return diagnostics
+        pool_stats = _connection_pool.get_stats()
+        conn_info = pool_stats["connections"].get(device_key)
+        if conn_info and conn_info["alive"]:
+            # Pool already has a live connection — device is reachable
+            diagnostics["tests"]["tcp_connection"] = {
+                "status": "pass",
+                "message": f"TCP connection alive in pool for {cfg.host}:{cfg.tcp_port}"
+            }
+        else:
+            # Acquire through the pool (opens new if needed, keeps it cached)
+            reader, writer, from_cache = await _connection_pool.acquire(
+                device_key, cfg.host, cfg.tcp_port, timeout=3.0
+            )
+            await _connection_pool.release(device_key, reader, writer, cfg.host, cfg.tcp_port)
+            diagnostics["tests"]["tcp_connection"] = {
+                "status": "pass",
+                "message": f"TCP connection successful to {cfg.host}:{cfg.tcp_port}"
+            }
     except Exception as e:
         diagnostics["tests"]["tcp_connection"] = {
             "status": "fail",
-            "message": f"Connection error: {str(e)}"
+            "message": f"Connection error to {cfg.host}:{cfg.tcp_port}: {str(e)}"
         }
         diagnostics["overall_status"] = "fail"
         return diagnostics
 
-    # Wait a bit after connection test to let device settle
-    await asyncio.sleep(1.5)
-
     # Test 5: Device responds to commands
     # Use longer timeout to account for rate limiting (device requires ≥1s between commands)
     client = NL43Client(cfg.host, cfg.tcp_port, timeout=10.0, ftp_username=cfg.ftp_username, ftp_password=cfg.ftp_password)

app/services.py

@@ -242,8 +242,8 @@ async def _get_device_lock(device_key: str) -> asyncio.Lock:
 
 # Configuration via environment variables
 TCP_PERSISTENT_ENABLED = os.getenv("TCP_PERSISTENT_ENABLED", "true").lower() == "true"
-TCP_IDLE_TTL = float(os.getenv("TCP_IDLE_TTL", "120"))           # Close idle connections after N seconds
-TCP_MAX_AGE = float(os.getenv("TCP_MAX_AGE", "300"))             # Force reconnect after N seconds
+TCP_IDLE_TTL = float(os.getenv("TCP_IDLE_TTL", "300"))           # Close idle connections after N seconds
+TCP_MAX_AGE = float(os.getenv("TCP_MAX_AGE", "1800"))            # Force reconnect after N seconds
 TCP_KEEPALIVE_IDLE = int(os.getenv("TCP_KEEPALIVE_IDLE", "15"))  # Seconds idle before probes
 TCP_KEEPALIVE_INTERVAL = int(os.getenv("TCP_KEEPALIVE_INTERVAL", "10"))  # Seconds between probes
 TCP_KEEPALIVE_COUNT = int(os.getenv("TCP_KEEPALIVE_COUNT", "3"))  # Failed probes before dead