Production-oriented documentation for qu, a small distributed uptime monitor that votes on the health of HTTP/TCP/ICMP targets across a cluster of cooperating nodes.

The top-level README.md is the marketing pitch and quick-start. The pages here go deeper and are organised by what you're trying to do.

Getting set up

Installation — pre-built binaries, building from source, verifying release artifacts, what the install script does.
Configuration — node.yaml, cluster.yaml, trust.yaml, environment variables, file layout, defaults.

Running it

Architecture — how nodes form quorum, how a master is elected, how cluster state replicates, what happens during a partition, and exactly which guarantees the design gives you.
Operations — day-2 tasks: upgrades, backups, recovery from a lost node, recovery from a lost quorum, monitoring qu itself.
Security — the mTLS / TOFU trust model, what the cluster secret protects, how to rotate keys, what to put on a public network and what not to.
Troubleshooting — common failure modes with the log lines you'll see and the fix.

Deployment recipes

Pick the one that matches your environment. They share most of the operational guidance — what differs is how qu is packaged and how the inter-node link is secured at the network layer.

systemd on bare metal / VM — single static binary, hardened unit file, CAP_NET_RAW for ICMP.
Docker / docker-compose — official image, single-node and multi-node compose files, persistent volumes.
Tailscale / WireGuard overlay — nodes in separate networks with no public ingress; cluster traffic stays on the tailnet.
Public-internet exposure — when you have no overlay and :9901 is reachable from the open internet: firewalling, rate-limiting, secret hygiene.

A note on stability

The wire protocol (internal/transport) and the on-disk format (cluster.yaml, node.yaml, trust.yaml) are considered stable within a minor version. Breaking changes will bump the major version and ship with a migration note.