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===== List of metrics =====

All metrics are exported through a single ''/metrics'' endpoint in Prometheus text format. The name follows the rules of Prometheus: ''epdg_<group>_<name>[_unit]'', the Counter type has the suffix ''_total'', Histogram is the suffix ''_seconds''/''_bytes''.

==== 1. Config (2) ====

^ Name ^ Type ^ Appointment ^
| ''epdg_config_status'' | Gauge | Component configuration status (0=error, 1=ok) |
| ''epdg_config_reload_total'' | Counter | Configuration download counter (success/failure) |

==== 2. Network (1) ====

^ Name ^ Type ^ Appointment ^
| ''epdg_network_connection_status'' | Gauge | TCP/UDP connection status to a node (0=down, 1=up) — applies to PGW (S2b), AAA (SWm), HSS (SWx) |

==== 3. IKEv2 SWu (3) ====

^ Name ^ Type ^ Appointment ^
| ''epdg_ikev2_messages_total'' | Counter | IKEv2 Message Counter (IKE_SA_INIT / IKE_AUTH / CREATE_CHILD_SA / INFORMATIONAL) |
| ''epdg_ikev2_request_duration_seconds'' | Histogram | IKEv2 response time |
| ''epdg_ikev2_errors_total'' | Counter | IKEv2 errors (NO_PROPOSAL_CHOSEN, AUTHENTICATION_FAILED, INVALID_SYNTAX, etc.) |

==== 4. GTPv2-C S2b (4) ====

^ Name ^ Type ^ Appointment ^
| ''epdg_gtp_messages_total'' | Counter | GTPv2-C (Create/Modify/Delete Session, Echo) |
| ''epdg_gtp_request_duration_seconds'' | Histogram | Waiting time request → reply |
| ''epdg_gtp_errors_total'' | Counter | GTP-C error by Cause Code |
| ''epdg_gtp_retransmissions_total'' | Counter | Redirecting GTP-C requests |

==== 5. GTP-U data plane (3) ====

^ Name ^ Type ^ Appointment ^
| ''epdg_gtpu_packets_total'' | Counter | Packages via GTP-U tunnel (uplink/downlink) |
| ''epdg_gtpu_bytes_total'' | Counter | Bytes through GTP-U tunnel |
| ''epdg_gtpu_errors_total'' | Counter | Tunneling errors (TEID mismatch, decap fail) |

==== 6. Diameter SWm/SWx/S6b (5) ====

^ Name ^ Type ^ Appointment ^
| ''epdg_diameter_messages_total'' | Counter | DER/DEA (SWm), MAR/MAA (SWx), AAR/AAA (S6b), STR/STA|
| ''epdg_diameter_request_duration_seconds'' | Histogram | Waiting time request → reply by Diameter |
| ''epdg_diameter_errors_total'' | Counter | Errors by Experimental-Result-Code |
| ''epdg_diameter_watchdog_status'' | Gauge | DWR/DWA watchdog status to node (0=timeout, 1=ok) |
| ''epdg_diameter_connection_status'' | Gauge | Diameter connection status to node (0=disconnected, 1=connected) |

==== 7. Service KPI (4) ====

^ Name ^ Type ^ Appointment ^
| ''epdg_service_attach_total'' | Counter | Attempts to connect (success/failure) via APN |
| ''epdg_service_attach_duration_seconds'' | Histogram | Duration of connection (IKE_SA_INIT → session ready) |
| ''epdg_service_availability'' | Gauge | Accessibility flag (0=down, 1=up) |
| ''epdg_service_uptime_seconds'' | Gauge | Service availability time |

==== 8. Session State (4) ====

^ Name ^ Type ^ Appointment ^
| ''epdg_session_ike_sa_total'' | Gauge | Active IKE SA |
| ''epdg_session_child_sa_total'' | Gauge | Active Child SA (IPSec tunnels) |
| ''epdg_session_gtp_sessions_total'' | Gauge | Active GTP-C sessions on S2b |
| ''epdg_session_subscribers_total'' | Gauge | Unique subscribers (UE connected) |

==== 9. Application (3) ====

^ Name ^ Type ^ Appointment ^
| ''epdg_app_threads_total'' | Gauge | Total number of work streams |
| ''epdg_app_memory_bytes'' | Gauge | Process memory by type |
| ''epdg_app_log_messages_total'' | Counter | Log messages by level (debug/info/warn/error/fatal) |

==== 10. System (4) ====

^ Name ^ Type ^ Appointment ^
| ''epdg_system_cpu_usage_percent'' | Gauge | Download CPU |
| ''epdg_system_memory_bytes'' | Gauge | System memory |
| ''epdg_system_disk_bytes'' | Gauge | Disk space |
| ''epdg_system_open_fds'' | Gauge | Open file descriptions |

==== Types of metrics (reminder) ====

^ Type ^ Appointment ^
| **Counter** | Monotonically growing counter (messages, errors, reboots) |
| **Gauge** | Current value (active sessions, memory, status) |
| **Histogram** | Distribution of values with automatic slices over intervals (duration, lifetime) |