Module telemetry 

Available on crate features quic and std only.

OpenTelemetry metrics for endpoints and the connections they carry.

Nothing is recorded unless an endpoint is built with EndpointBuilder::with_metrics.

A connection is recorded once, at its first terminal outcome: its duration runs from creation to that outcome, and its UDP totals are the ones it had then, so traffic of a closing or draining period that follows is not counted. Connection series carry quic.side (client, server) and quic.version (1, 2, other); ended connections also carry quic.close.reason and quic.handshake.completed:

• quic.connection.duration and quic.connection.closed;
• quic.connection.handshake.duration, recorded when the handshake completes;
• quic.connection.bytes {direction = sent, received}: UDP payload bytes;
• quic.connection.lost_packets: packets declared lost on the connection’s last path;
• quic.connection.datagrams.gated {direction}: datagrams the datagram gates dropped.

Endpoint counters are read on collection and summed over every endpoint built with the same QuicMetrics (or a clone of it), dropped endpoints included, so a total never falls. Two separately created QuicMetrics report the same series unless their MeterOptions attributes tell them apart. Exported endpoint counters:

• quic.endpoint.handshakes {outcome = accepted, outgoing, refused, ignored}: refused and ignored are attempts the application refused or ignored;
• quic.endpoint.handshakes.expired: attempts that expired before the application took them;
• quic.endpoint.admission.refused {reason = at_limit, per_source, unvalidated} and quic.endpoint.admission.retried: attempts the endpoint refused or answered with a Retry under load, before the application saw them;
• quic.endpoint.datagrams.received, and quic.endpoint.datagrams.dropped for those a saturated receive queue dropped;
• quic.endpoint.receive.truncated_entries: receive entries discarded whole for a truncated datagram (entries, not datagrams);
• quic.endpoint.receive.errors_ignored: receive errors ignored as injectable noise;
• quic.endpoint.responses.dropped {reason = queue_full, send_failed}: stateless responses that never left.

Occupancy (attempts in progress, queue use, retained sockets) is not exported; it is in Endpoint::stats.

Structs

QuicMetrics

Metrics shared by the endpoints built with it, and by their connections.