qlog

Write a qlog trace of every QUIC connection the proxy makes or accepts, to read in qvis or with jq. Use this page to debug QUIC and HTTP/3 behaviour (handshakes, loss, congestion); it is not meant for production.

qlog. With --qlog-dir <dir> (Http3Options.Builder.qlogDirectory, qlog_dir), each of the proxy's QUIC connections, to clients and to servers, writes a qlog trace into <dir>, whether or not metrics are on: <ODCID>_server.sqlog or <ODCID>_client.sqlog, named after the connection's original Destination Connection ID and the proxy's side of it. A file is JSON-SEQ (RFC 7464), as the qlog main schema serializes a trace: each record starts with the record separator (0x1E) and ends with a newline. The first is the header ("qlog_version":"0.3", "qlog_format":"JSON-SEQ", the vantage point, and ODCID and group_id in common_fields, with "time_format":"relative" and the wall-clock reference_time); then one record per event, {"time":<ms since the first event>,"name":"transport:packet_sent","data":{...}}, with the quic module's events: packets sent, received and lost, key updates, state changes and the connection's close. The directory keeps at most --qlog-max-files files (1000 by default; the oldest the proxy wrote are deleted), and a file stops at 64 MiB (qlogMaxFileBytes). qlog builds an event for every packet, so it is for debugging.

java -jar microproxy.jar --port 8443 --http3 --listener-keystore proxy.p12 --qlog-dir /tmp/qlog
# Open the files in qvis (https://qvis.quictools.info), or read them with jq --seq:
jq --seq -c 'select(.name == "recovery:packet_lost")' /tmp/qlog/*_server.sqlog