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Last active August 11, 2018 04:22
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ot2-pause-handler
Raw
.gitignore
node_modules
Raw
README.md

OT2 Pause Handler

Setup

Requirements

  • Node v8 LTS
  • npm v6
    • Once Node is installed, use npm to upgrade itself
    • npm install --global npm@latest
  • Clone or download this repository
    • git clone https://gist.github.com/3ba833f8cc7252e7cb5e84cfae4554fe.git ot2-pause-handler
    • Or Download it as ZIP

Once downloaded

# install dependencies
cd path/to/ot2-pause-handler
npm install

Usage

  1. Open the Opentrons App
  2. Upload your protocol with a robot.pause command
  3. Start the script with:
# by default, use USB-to-ethernet adapter address
node index.js

# specify a different IP (e.g. for WiFi)
node index.js "192.168.1.100"
  1. Click "Run" in the app
  2. Script will detect when protocol goes from running to paused and run its doYourThing function
Raw
index.js
// checking OT2 RPC websocket for session state changes
'use strict'
const execa = require('execa')
const WebSocket = require('ws')
const {get, uniqueId} = require('lodash')
// get host and port from command line, defaulting to USB-to-ethernet address
const argv = process.argv.slice(2)
const HOST = argv[0] || '[fd00:0:cafe:fefe::1]'
const PORT = argv[1] || 31950
// RPC message types
const TYPE_NOTIFICATION = 2
const TYPE_CONTROL = 3
// RPC notification topics
const TOPIC_SESSION = 'session'
// session states
const STATE_RUNNING = 'running'
const STATE_PAUSED = 'paused'
let ws
let sessionId = null
let previousState = null
// start
initializeRpcClient()
// YOUR CODE HERE
function doYourThing() {
console.log('Doing your thing')
// example shell command to run
execa('sleep', ['1'])
// once the shell command has finished executing, call `resume`
.then(() => call('resume'))
.catch(console.error)
}
function initializeRpcClient () {
const url = `ws://${HOST}:${PORT}`
console.log('Connecting to', url)
ws = new WebSocket(url)
// listen for RPC JSON messages on the websocket
ws.on('message', handleMessage)
}
function call (name, args = []) {
if (!sessionId) {
return console.error("Can't resume because we don't have a session")
}
console.log(`Calling method "${name}" on session ${sessionId}`)
// send a remote call of `resume` on the session object
ws.send(JSON.stringify({
$: {token: uniqueId('token')},
id: sessionId,
name,
args
}))
}
function handleMessage (data) {
const message = parseMessage(data)
// check the message metadata for the type of message
if (message.$.type === TYPE_NOTIFICATION) {
// if it's a notification, pull out the session state and handle do your
// thing if the state changed from running to paused
const {topic, payload: {state}} = getNotificationProps(message)
if (topic === TOPIC_SESSION) {
if (previousState === STATE_RUNNING && state === STATE_PAUSED) {
console.log(`Session changed from running to paused`)
doYourThing()
}
previousState = state
}
} else if (message.$.type === TYPE_CONTROL) {
// if it's the control message (initial message sent by server), grab
// the session ID from the message to make RPC calls later on
sessionId = get(message, 'root.v.session_manager.v.session.i')
if (!sessionId) {
throw new Error('Protocol must be loaded before starting this utility')
}
console.log('Listening to session', sessionId)
}
}
function parseMessage (data) {
try {
return JSON.parse(data)
} catch (e) {
console.warn('Parse error', e)
return {}
}
}
function getNotificationProps(message) {
let {topic, payload} = get(message, 'data.v', {topic: null, payload: null})
return {topic, payload: get(payload, 'v')}
}
Raw
package-lock.json
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}
Raw
package.json
{
"name": "ot2-pause-handler",
"private": true,
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"keywords": [],
"author": "Mike Cousins <mike@opentrons.com>",
"engines": {
"node": ">=8",
"npm": ">=6"
},
"license": "Apache-2.0",
"dependencies": {
"execa": "^0.10.0",
"lodash": "^4.17.10",
"ws": "^6.0.0"
}
}
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