Module node_status 

Compact node status and identity for the auxiliary radio lane.

An operator paired only to a ground station sees the drone it relays as a bare row: no capabilities, no services, no board. Everything the fleet view wants lives on the drone’s own /api/status, and the WFB link carries no IP, so none of it reaches the ground node. This module is the wire shape that closes that gap, carried on the auxiliary lane’s status and identity channels.

Why a dedicated schema and not the heartbeat payload

The cloud heartbeat already assembles exactly these facts, but its payload is a hundred-plus camelCase fields sized for an HTTP POST. One aux frame carries AUX_MAX_PAYLOAD = 1200 bytes, and the lane is shared with MAVLink at telemetry rates. So this is a deliberately separate, deliberately small projection: the fields a ground operator acts on, and nothing else.

Two economies do the work. The encoding is msgpack rather than JSON, matching the state socket’s v2 form. Field names are two or three characters, because msgpack writes map keys as strings and twenty-odd long names would spend several hundred bytes on nothing but labels. Every field is documented here, which is where the readability lives.

Absent means unknown, never zero

Every optional field is skip_serializing_if, so a fact the drone could not read is ABSENT from the frame rather than sent as a plausible-looking 0 or false. A ground reader shows “unknown”, never a fabricated reading. This is also what keeps the frame small in practice: a node with no flight controller spends no bytes saying so.

Trimming, not fragmentation

A snapshot that will not fit is TRIMMED, in a fixed order, until it does. It is never split across frames.

Fragmentation was considered and rejected. It would need a reassembly buffer, a reassembly timeout, and a partial-frame policy on the receiving side, and on a lossy radio lane one dropped fragment discards the whole snapshot anyway. Status is periodic and idempotent: losing one costs a second, and the next is complete. Trimming keeps the receiver a pure function of one datagram with no cross-frame state to get wrong.

In practice trimming never fires. A fully-populated snapshot measures a few hundred bytes against a 1200-byte budget, and a test pins the worst case with every field at its maximum length. The ladder exists so that a future field, or an unusually long board name, degrades predictably instead of silently failing to send.

Bounded by construction

Every variable-length field is capped at build time by the NodeStatus builders and NodeIdentity::build — strings truncated, the failed-service list capped at MAX_FAILED_NAMES. The cap is not a formality: the failed-unit list is the one field an operator most wants and the one that grows without bound on a badly broken node, which is exactly when the lane must not be flooded.

Structs

NodeIdentity

A drone’s identity, sent less often than status because it does not change.

NodeStatus

A compact projection of a node’s status, sized for one aux frame.

Constants

MAX_DEVICE_ID

Longest device id carried. Real ids are 12 hex characters, so this is headroom rather than a limit that bites.

MAX_FAILED_NAMES

Most failed-unit names carried in one snapshot.

MAX_NAME

Longest human-facing node name carried.

MAX_PLUGIN_LIST

Longest plugin-inventory string carried: pluginId@contractVersion entries joined by commas. Capped so a node with many plugins degrades predictably instead of overflowing the frame; a real node runs a handful.

MAX_SHORT

Longest short free-text field (agent version, board name, SoC, firmware family, camera and video state).

MAX_UNIT_NAME

Longest single failed-unit name carried.

NODE_STATUS_VERSION

Schema version for both the status and identity frames.

Functions

parse_plugin_list

Parse a plugin-inventory string produced by plugin_list_string back into (id, contractVersion) pairs. A malformed entry is skipped rather than failing the whole parse, so one bad token never blinds a version check.

plugin_list_string

Format an installed-plugin inventory as id@ver entries joined by commas, sorted by id so the string is stable regardless of install order. None when the inventory is empty. Plugin ids are reverse-DNS and carry no @, so the last @ always separates id from version on decode.