Metadata key carrying the serialized OpenTelemetry propagation context, so a
trace can be continued across a dora message hop. Read via
Metadata::open_telemetry_context; stamped by the node and runtime send
paths when tracing is enabled. Keep this the single source of truth so the
write and read sides can never drift.
Metadata key carrying the FNV-1a hash (as an i64) of the Arrow IPC schema
for a zenoh data message. Present on schema-once messages so a receiver can
tell which primed decoder a schema-less batch belongs to and detect schema
changes. Absent on messages a receiver should decode as a standalone full
stream (large/SHM and daemon-path payloads).
FNV-1a-64 hash with a fixed seed (cross-process deterministic). Used to
fingerprint an Arrow IPC schema block so a schema-less batch can be matched
to the schema it was encoded against (see SCHEMA_HASH). The producer
node, the consumer node, and the daemon’s dora topic debug path all hash
the same schema-block bytes with this function, so the value must stay
identical across crates — keep this the single source of truth.
Remove internal wire-protocol keys (SCHEMA_HASH, FRAMING) from a
parameter map. Call this at every wire→user boundary: the keys are
meaningless after decode, and a stale SCHEMA_HASH forwarded from an
input’s metadata into send_output parameters (a standard pattern, e.g.
replay) would ride onto outputs that don’t overwrite it, making receivers
hash-mismatch and silently drop them (dora-rs/dora#2366 review).