Command a machine with a row

The physical worldMQTTSDKHTTPMachines.commandRowMachines.commandTargetMachines.CommandResolutionconditional

Start, stop, pause or change over a machine by parking a row on its role; the machine's reply resolves the row as data.

The situation

An order needs the bonding cell changed over to a new recipe before its units arrive. The workflow should ask the machine the way it asks a person for anything, and read the answer as data, including “the machine never answered”.

The recipe

import { conditional, Machines } from '@hotmeshio/long-tail';

const target = Machines.commandTarget(line, 'bond-01');
const reply = await conditional<Machines.CommandResolution>(`changeover-${orderId}`, {
  ...Machines.commandRow(target, 'changeover', { recipe: { id: 'RCP-BOND-B', version: '1' } }),
  timeout: '10m',
});

commandRow builds a machine-command row on the machine’s role. The gateway sends the command and resolves the row with the reply, as the machine that gave it:

{ accepted: true, machineId: 'bond-01', op: 'changeover', status: 'accepted',
  reason: 'changing over to RCP-BOND-B v1' }

`status`	Meaning
`accepted`	The machine took the command
`refused`, `failed`	The machine said no; the reason is in `reason`
`no-reply`	No reply after every attempt; the command expired
`unsupported`	Not a command a row may ask for, or not a machine on this line; nothing was sent

Commands a row may ask for: start, stop, pause, resume, changeover and cancel (which needs args.jobId).

The guarantee

Asking a machine takes the same access as parking any row on its role: write access to that role, or a workflow that parks the row. A row commands only the machine whose role it is on. A no-reply command expired at the end of the asking, so a copy that reaches the machine later is refused, never run. See Machines.

The physical world