Add a dedicated UNIBUS_NATS_MONITOR=1 toggle that opens the embedded
nats-server monitoring HTTP endpoint (127.0.0.1:8222, loopback only) so a
local metrics scraper can read /varz, /connz and /jsz for server-level
metrics (msgs/s, connections, KV bucket msgs, RAFT leader per stream,
restarts).
Previously the monitoring endpoint was only reachable via UNIBUS_NATS_DEBUG=1,
which is coupled to the verbose nats-server debug log: enabling the endpoint
also wrote routes/RAFT/room subjects to journald in clear, which regresses the
hardened posture (issue 0007). The two concerns are now decoupled.
The toggle computation is extracted to a pure function
natsLogOpts(debugEnv, monitorEnv) (noLog, debug, trace, monitor): MONITOR=1
opens the endpoint while keeping the log quiet (NoLog true / Debug false). The
inverse coupling is preserved for backward compatibility (DEBUG still implies
MONITOR). The 127.0.0.1 bind stays hardcoded — the monitoring endpoint has no
auth and must never be reachable from the network.
Deploy wiring versioned: additive systemd drop-in
membershipd-cluster.service.d/nats-monitor.conf (Environment=UNIBUS_NATS_MONITOR=1)
plus a "NATS server metrics" section in the cluster README with the rolling
activation runbook (magnus -> homer -> datardos) gated on R3 reconvergence
(followers 2/2) between nodes.
Tests: pure decoupling table (monitor on => log NOT debug; debug => monitor;
default closed) + a real embedded server with MONITOR=1 asserting /varz answers
200 on loopback:8222, and a server without the flag with the endpoint closed.
100% additive: behavior is identical without the flag. Bump app.md 0.10.0 ->
0.11.0.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Egutierrez