Observability

A Live session produces three kinds of signal:

• Traces. Each session is one live_session span carrying gen_ai.conversation.id (the persistence session id when set, else the transport’s). Every turn is a turn span beneath it, and each tool call, VAD edge, interruption and transcript is logged inside its turn.

• Metrics, all prefixed gemini_genai_rs_:

  Metric	Kind	What
  connections_total, sessions_active	counter, gauge	Live sessions connected, open now
  reconnections_total	counter	reconnects (GoAway or a dropped connection)
  ws_bytes_sent_total, ws_bytes_received_total	counter	Live wire traffic
  response_latency_ms	histogram	end of user speech (or text) to the model’s first output
  tool_calls_total, tool_call_duration_ms	counter, histogram	by function
  tokens_total	counter	by direction (prompt, response) and modality (TEXT, AUDIO, IMAGE, VIDEO), per turn
  http_requests_total, http_request_duration_ms	counter, histogram	REST calls

• In-process telemetry. SessionTelemetry counts the same things for one session. Its snapshot() includes tokens_by_modality. The web UI’s DevTools panels show it.

Turning export on

Configuration comes from the environment through TelemetryConfig::from_env():

Variable	Effect	Feature
OTEL_EXPORTER_OTLP_ENDPOINT	export traces and metrics over OTLP/gRPC to that collector	otel-otlp
ADK_TELEMETRY=gcp	export to Cloud Trace and Cloud Monitoring (project from GOOGLE_CLOUD_PROJECT, else detected)	otel-gcp
OTEL_SERVICE_NAME	the service name (default gemini-live)
ADK_METRICS_ADDR	serve Prometheus metrics at this address, e.g. 0.0.0.0:9464	metrics
RUST_LOG	log filter (default info)

An application that owns its subscriber can call TelemetryConfig::init() (or init_gcp()). One that builds its own subscriber, for example to add a layer, builds the exporters and attaches their layer:

use gemini_genai_rs::telemetry::TelemetryConfig;
use tracing_subscriber::prelude::*;

let config = TelemetryConfig::from_env();
config.install_metrics()?;               // Prometheus, if ADK_METRICS_ADDR is set
let exporters = config.build_otlp()?;    // or build_gcp().await
tracing_subscriber::registry()
    .with(tracing_subscriber::fmt::layer())
    .with(my_layer)
    .with(exporters.layer())
    .init();
let _guard = exporters.guard;            // hold for the life of the process

The web UI does exactly this when it is built with --features otel-otlp or --features otel-gcp:

OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317 \
  cargo run -p gemini-adk-web-rs --features otel-otlp

Metrics are recorded through the metrics facade. They go nowhere until a recorder is installed, such as the Prometheus endpoint above.

What is not exported

Transcript text, tool arguments and results appear in logs at debug and info. They are not span attributes, so a trace backend doesn’t receive them unless you ship logs there too. See hardening for what redaction does and does not cover.