## Why
A busy Puppetboard re-fans-out the same /facts query every few seconds, and a
502 is worse than 30-second-old facts when every PuppetDB is unreachable.
## How
- Add a `Cache` interface (get reports fresh/stale/miss, put, stats) keyed on
`<path>?<params>` with keys and repeated values sorted, plus a no-op default
so uncached paths behave exactly as before.
- Route serveMerged/serveUnion/serveSummed through `serveCached`, so the
reports cache drops in at `cacheFor` without touching a handler.
- Back /facts and /nodes with a byte-bounded LRU: `facts_ttl` (default 30s,
clamped to a 30s cap) and `facts_cache_bytes` (default 64 MiB); expired
entries are kept and served only when every backend fails.
- Single-flight identical keys so N concurrent requests cause one fan-out.
- Surface `cache` state and `serving_stale` in /healthz and the cache settings
in `config show`.
Remove hardcoded internal PuppetDB URLs and site-specific wording so the
project is publishable as-is.
- backends have no default; require config file or PDBMUX_BACKENDS
- primary/prefer default to the first configured backend
- config init writes example.com placeholders
- Load no longer validates, so config init/version work unconfigured
- genericise README, package doc, help text and Dockerfile comment
Split out from node-lookup PR #17 into its own repo. pdbmux presents a
single merged PuppetDB v4 query surface over the old (Consul) and new
(k8s) PuppetDBs during the VM to k8s migration, and is deployed in-cluster
via argocd-apps as a container image.
unkin-agent
benvin