Module telemetry 

Telemetry: tracing spans, metrics, and structured events for client calls.

This is the transport-neutral instrumentation the client crates wrap their RPCs with (Option B: telemetry lives in canton-core). Every instrumented call opens a canton.rpc tracing span, emits request/error counters via the metrics facade, and logs a structured success/error event.

Exporting. Following the standard Rust telemetry model, this crate emits and the application chooses the exporters: a tracing_subscriber for logs and spans, a metrics recorder for counters. Metrics carry method + transport labels, so any recorder (Prometheus, an OTLP bridge, …) gets the per-endpoint request/error breakdown for free (success = requests − errors).

The otel feature supplies a supported OpenTelemetry path for both halves rather than leaving it as an exercise: otel::otlp_tracer builds the span exporter, otel::otlp_metrics builds the metrics pipeline and installs the recorder that bridges this crate’s counters onto it, and trace context is injected into every outgoing request — gRPC metadata, JSON headers, and the WebSocket upgrade — automatically.

Streams. Use instrument for a call that returns a value and instrument_stream for one that returns a stream. The difference is not cosmetic: a subscription’s outcome is not known when it opens, so instrumenting only the opening records every long-lived stream as a success and never revisits it.

Modules

otelotel

OpenTelemetry export helpers (enable the otel feature).

Constants

METRIC_ERRORS

Counter: client errors, labelled by method, transport, and retriable.

METRIC_REQUESTS

Counter: total client requests, labelled by method and transport.

TRANSPORT_GRPC

transport label / span-field value for the gRPC lane.

TRANSPORT_JSON

transport label / span-field value for the JSON lane.

Functions

current_trace_id

The current span’s trace id as 32 hex characters, when an OpenTelemetry context is active.

instrument

Instrument a client RPC future: open a canton.rpc span, count the request (and any error), and log a structured outcome event.

instrument_stream

Instrument a client stream: the same span, counters and events as instrument, but for the life of the stream rather than the moment it opens.