Observability

Ella IMS supports four observability pillars: Metrics, Traces, Logs and Profiles.

Metrics

Ella IMS exposes Prometheus metrics at GET /api/v1/metrics.

Metric	Type	Description
ellaims_build_info	Gauge	Always 1. The version and revision of the running build are in its labels.
ellaims_registered_subscribers	Gauge	Subscribers registered now.
ellaims_registration_attempts_total	Counter	Registrations and re-registrations, by result: accept, auth_failure, reject.
ellaims_active_calls	Gauge	Calls in progress.
ellaims_calls_total	Counter	Calls that ended, by outcome: answered, cancelled, busy, rejected, no_answer, unavailable, failed.
ellaims_sip_responses_total	Counter	Final responses the P-CSCF sent to phones, by method and status class.
ellaims_sip_request_duration_seconds	Histogram	Time from a request of a phone to the final response the P-CSCF sent, by method and status class, the answer of the far end included when the request is forwarded. INVITE is left out: its final response waits for the callee.
ellaims_diameter_peer_up	Gauge	1 if the connection to a Diameter peer is open, by peer and application.
ellaims_peer_requests_total	Counter	Requests to the HSS, the policy function, the SMSCs and the MMEs and SMSFs, by interface (cx, rx, n5, sh, s6c, sgd) and result (success, failure, error, timeout).
ellaims_peer_request_duration_seconds	Histogram	Duration of requests to the HSS, the policy function, the SMSCs and the MMEs and SMSFs, by interface.
ellaims_ipsmgw_short_messages_total	Counter	Short messages the IP-SM-GW carried, by direction (mo, mt), domain (smsc for mo; ims, mme, sgsn, smsf_3gpp, smsf_non_3gpp, none for mt, the last tried) and result (success, failure).
ellaims_api_request_duration_seconds	Histogram	Duration of API requests, by method, route (/api/v1/users/{email}) and status code. Requests to /api/v1/pprof/ and to no route are left out.
ellaims_database_query_duration_seconds	Histogram	Duration of database calls, by connection pool: write, read.
ellaims_database_query_errors_total	Counter	Failed database calls, by connection pool.
ellaims_database_storage_bytes	Gauge	Size of the database on disk, by file: main, wal.
go_*	Gauge, Counter, Summary	Go runtime: goroutines, heap, garbage-collection pauses.
process_*	Gauge, Counter	Process: memory, CPU, open file descriptors, start time.

Traces

Ella IMS exports OpenTelemetry traces when telemetry.enabled is set in the configuration file.

Property	Value
Export	OTLP over gRPC, without TLS
Service	ella-ims
Sampling	Parent-based, always on for a trace the IMS starts
Propagation	W3C Trace Context
Error status	HTTP and SIP: a server span from a 5xx response, a client span from a 4xx, except a SIP 401 or 407 challenge. Diameter: a client span from a Result-Code from 3000.
SIP trust domain	Trace context is read and sent on SIP only within the trust domain: the IMS's own addresses, and for the I-CSCF, the S-CSCF and the MCPTT AS, sip.trusted_networks. It never reaches a phone.

Spans

Span	Kind	Description
{method} {route}	Server	A request to the API, except /api/v1/livez, /api/v1/readyz, /api/v1/metrics and /api/v1/pprof/. Links to the caller's traceparent.
{method} {url.template}	Client	A request to the PCF on N5.
POST /n5/v1/sessions/{id}/{notify,terminate}	Server	A notification from the PCF on N5.
Cx/{command}, Sh/{command}, Rx/{command}, S6c/{command}, SGd/{command}	Server, Client	A Diameter request.
{method}, such as INVITE	Server, Client	A SIP transaction, until its final response. A request from a phone starts a trace, linked to the INVITE of its call or the REGISTER it renews.
registration expiry, media loss, …	Internal	Work that starts later than its cause, as on a timer or after a settings change: a new trace, linked to its cause.

Attributes

Attribute	Values
ella.ims.role	pcscf, icscf, scscf, mcptt, ipsmgw, or ims for work of the IMS as a whole
sip.call_id	The Call-ID of a SIP span
ella.ims.icid	The ICID of P-Charging-Vector of a SIP span, which joins it to its call record

Logs

Field	Description
trace_id	Trace ID of the span the event happened in. Absent outside a span.
span_id	Span ID of the span the event happened in. Absent outside a span.

Profiles

Ella IMS exposes the net/http/pprof API at /api/v1/pprof/.