fix: replace broad except Exception with specific exception types

- jail_service: catch ValueError (fail2ban protocol error) instead of Exception
- health.py: catch AttributeError (not OSError/TypeError) for defensive checks
- ban_service: re-raise programming errors in geo lookup handlers
- server_service: catch Fail2BanConnectionError, Fail2BanProtocolError, ValueError
- config_writer: catch OSError instead of Exception

Programming errors now bubble to global handler instead of being silently caught.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/app/routers/health.py

@@ -84,7 +84,7 @@ async def health_check(
             components.append(
                 ComponentHealth(name="scheduler", healthy=False, message="Not initialised"),
             )
-    except Exception:  # pragma: no cover - defensive
+    except AttributeError:  # pragma: no cover - defensive
         scheduler_state = "unknown"
         components.append(
             ComponentHealth(name="scheduler", healthy=False, message="Not accessible"),
@@ -100,10 +100,11 @@ async def health_check(
             components.append(
                 ComponentHealth(name="cache", healthy=False, message="Not initialised"),
             )
-    except Exception:  # pragma: no cover - defensive
+    except AttributeError:  # pragma: no cover - defensive
         cache_state = "uninitialised"
-
+        components.append(
-    # --- fail2ban ---
+            ComponentHealth(name="cache", healthy=False, message="Not accessible"),
+        )
     fail2ban_online: bool = server_status.online
     if not fail2ban_online:
         components.append(

backend/app/services/ban_service.py

@@ -481,6 +481,7 @@ async def list_bans(
                 log.warning("ban_service_geo_lookup_failed", ip=ip)
             except Exception as exc:
                 log.error("ban_service_geo_lookup_unexpected_error", ip=ip, error=type(exc).__name__)
+                raise  # Bubble programming errors to global handler
 
         items.append(
             DomainDashboardBanItem(
@@ -648,7 +649,7 @@ async def bans_by_country(
                 return ip, None
             except Exception as exc:
                 log.error("ban_service_geo_lookup_unexpected_error", ip=ip, error=type(exc).__name__)
-                return ip, None
+                raise  # Bubble programming errors to global handler
 
         results = await asyncio.gather(*(_safe_lookup(ip) for ip in unique_ips))
         geo_map = {ip: geo for ip, geo in results if geo is not None}

backend/app/services/jail_service.py

@@ -159,12 +159,13 @@ async def _check_backend_cmd_supported(
         if state.backend_cmd_supported is not None:
             return state.backend_cmd_supported
 
-        # Probe: send the command and catch any exception.
+        # Probe: send the command and catch only fail2ban protocol errors.
+        # Programming errors (TypeError, AttributeError) bubble up to global handler.
         try:
             ok(await client.send(["get", jail_name, "backend"]))
             state.backend_cmd_supported = True
             log.debug("backend_cmd_supported_detected")
-        except Exception:
+        except ValueError:
             state.backend_cmd_supported = False
             log.debug("backend_cmd_unsupported_detected")
 

backend/app/services/server_service.py

@@ -14,7 +14,7 @@ from typing import cast
 
 import structlog
 
-from app.exceptions import ServerOperationError
+from app.exceptions import Fail2BanConnectionError, Fail2BanProtocolError, ServerOperationError
 from app.models.server_domain import DomainServerSettings, DomainServerSettingsResult
 from app.models.server import ServerSettingsUpdate
 from app.utils.constants import FAIL2BAN_SOCKET_TIMEOUT
@@ -79,7 +79,7 @@ async def _safe_get(
     try:
         response = await client.send(command)
         return ok(cast("Fail2BanResponse", response))
-    except Exception:
+    except (Fail2BanConnectionError, Fail2BanProtocolError, ValueError):
         return default
 
 

backend/app/utils/config_writer.py

@@ -150,7 +150,7 @@ def _write_parser_atomic(
         with os.fdopen(fd, "w", encoding="utf-8") as f:
             f.write(content)
         os.replace(tmp_path_str, str(path))
-    except Exception:
+    except OSError:
         with contextlib.suppress(OSError):
             os.unlink(tmp_path_str)
         raise