Power inventory and topology

Model how power reaches equipment, from the panel to the power supply, so operators can answer what loses power when a feed fails, which devices lack redundant supply, and how close each feed is to its limit. RFD 5 left power feeds, panels, outlets, and power paths to a later RFD; this is that RFD.

Power follows the same rule as the rest of Renga: planned connections, observed evidence, and the current topology stay distinct, and evidence never rewires the plan silently.

NetBox models power panels at a site or location, power feeds from a panel to a rack, power outlets on PDUs, and power ports on devices, joined by cables. A feed carries its supply type, phase, voltage, amperage, and maximum utilization; a power port carries its maximum and allocated draw. Renga keeps that shape and adds observed draw and supply health as evidence.

Every power object gets a resource envelope and typed projection, like the other DCIM objects.

The current power path of a device is the chain from each of its power ports through an outlet, its PDU, and the PDU’s inlet to a feed and panel. Renga computes it from current power connections; it is never stored as a separate truth. A port whose chain is incomplete shows where it stops.

Redundancy is a property of the path: a device is redundantly powered when its ports reach at least two feeds on different sides. A device with two supplies both on side a is not redundant, whatever its supply count says.

Electrical quantities retain their units: real power in W, apparent power in VA, and current in A. For AC, usable apparent capacity is voltage × amperage × maximum utilization for single-phase, or √3 × line-to-line voltage × line current × maximum utilization for balanced three-phase. Single-phase voltage is measured across the supply conductors. DC capacity is voltage × amperage × maximum utilization in W. The configured amperage is the circuit’s rated current, not an observed load.

Allocated real load sums the allocated input watts of ports on the feed’s path. AC conversion from W to VA requires an explicit per-load power factor (VA = W / power factor, with 0 < power factor ⇐ 1), including its provenance as configured or measured. Missing power factor leaves allocated apparent load and current headroom unknown; Renga does not silently assume unity or compare watts directly with VA. An owner may set one organization-wide default power factor; until then no default exists. Headroom computed from that default is labelled as resting on a configured default rather than a per-load value. Measured W, VA, current, and power factor remain separate evidence, with their measurement time and coverage.

Renga shows allocated and measured load side by side, comparing only compatible quantities. Watt totals alone are not verified circuit headroom or assurance that another server can safely be connected. Three-phase PDUs show current and allocated load per leg using that leg’s voltage and load assignment; the balanced aggregate formula cannot establish per-leg headroom. Missing leg assignments or conversion data show incomplete capacity, not spare capacity.

Nothing on the network knows a building’s electrical layout, so part of the model is always entered. Evidence fills in the rest, and Renga computes what follows from both.

Discovery can suggest a power connection (see Suggested connections) but never records one.

Inventory facts such as installed supplies arrive through observations. Timed power readings use the telemetry batches defined below, and every fact and reading records which source produced it.

Evidence never creates or removes a power connection. An outlet reporting draw with no connected port, or a supply reporting no input, opens a finding that an operator resolves, as LLDP evidence does for data cables in RFD 7.

Readings are sampled on their own interval (one minute by default) and delivered through a versioned telemetry payload. Each batch has a replay ID and retains the installation, source stream, collector, target, and sensor identities that produced every sample. A typed telemetry endpoint accepts each source/replay-ID pair idempotently; its payload cannot be mistaken for an inventory observation.

The agent persists telemetry in a separate queue namespace whose entries carry their payload type and destination. Entry, byte, and age limits apply only to that queue. When backpressure exceeds those limits, it drops the oldest telemetry batch, reports the lost batch count and time range in queue health, and never evicts an inventory observation. Delivery drains inventory first and caps telemetry work per pass, so a telemetry backlog cannot delay inventory or lease check-ins indefinitely. Telemetry acceptance does not advance inventory accepted/reconciled clocks, change snapshot completeness, retire inventory, or trigger reconciliation.

Renga keeps the latest reading of each quantity, with its time, source, and coverage, in its own current-reading tables using the event-time rules above. Findings and headroom use only eligible current readings; structural redundancy uses confirmed paths. A separate bounded correlation window supports connection suggestions as described above.

History sits behind a Renga.Telemetry.Store behaviour, which writes samples, and reads an organization-scoped time range in fixed buckets. Every bucket returns average, minimum, maximum, last, and sample count; a bucket with no samples is a gap and is never interpolated or returned as zero.

The store only feeds charts and trends. Swapping adapters, or losing the store, never changes current-reading eligibility, a finding, or a capacity figure. Store queries always include organization scope, and an external adapter must isolate that scope in its backend namespace and query. The behaviour is not specific to power; later RFDs may record other readings through it.

Findings join the Inbox under a Power domain and follow the existing workflow.

Mutations require the managed-inventory owner/admin policy.

UPS runtime modeling, generator and transfer-switch topology, cooling, power billing, and automatic outlet control. Switching an outlet would be an operate capability under RFD 9 and needs its own design.

Progress is tracked in the implementation checklist.