When Proxmox /nodes/{node}/status returns only total/used/free without
available/buffers/cached, EffectiveAvailable() returns Free (non-zero),
causing the RRD fallback gate to be skipped. This results in inflated
node memory where cache/buffers are counted as "used."
Widen the RRD fallback condition from requiring effectiveAvailable == 0
to triggering whenever missingCacheMetrics is true. Add negative caching
for failed RRD lookups (2-minute backoff) to avoid repeated retries.
rcourtman
32746e2d2a