TaskHub

Send it tasks, watch as they happen.

Important:

• This project is in early development and not all features are implemented yet.
• Backwards compatibility not guaranteed until version 1.x.x

Vocabulary

• server: The taskhub server.
• client: Both "clients" and "services" (that respond to clients) are referred to as clients here. A connection is an instance of a client.
• action: A category of tasks. Example of actions can be: "email:send", "geo:geocode", "email/address:validate". Actions are composed of: <noun>:<verb> or <noun>/<sub.noun>:<verb>
• task: An instance of an action, like a job.
• event: An event that updates the state of a task. See task lifecycle for complete event reference
• command: Messages sent to the hub. Either "pub" or "sub". Kind of like requests. Internal, not exposed in APIs.
• message: Messages sent from the hub to the clients. Kind of like responses. Internal, not exposed in APIs.

Task lifecycle

• init: A client asks to start this task.
• start: A task has been received by the hub and has been sent to subbing services. Event is triggered when one has started work on the task.
  • update: A service updates all other subbing services about an update.
  • drop: A service is done working on it without returning a result.
  • return: A service has returned a result, and thereby completed the task globally.
• success: A service has completed and returned a result. Task is considered complete and hub sends complete event to all subbing services.
• fail: A service failed or been cancelled.
• end: All subbing services have either timedout, succeeded or dropped, or the hub has cancelled/failed the task.

Examples

Server

const { Server } = require('taskhub');

const hub = new Server({
  port: 8080,
  // If hub waits longer than this for subscribing clients
  // the task has failed. Default value. Can be overridden per task.
  // NOT IMPLEMENTED YET.
  taskStartTimeout: 100,
  // IF a task takes longer than this to finish (either success or error)
  // hub will consider the task has failed and emit fail message.
  // Can be overridden per task.
  // NOT IMPLEMENTED YET.
  taskEndTimeout: 1000 * 60
});

hub.addCredentials('emailer', {
  // The client's authentication key
  key: '---super-secret-key---',
  // The actions the client is allowed to subscribe to.
  // NOT IMPLEMENTED YET.
  subPermissions: [ 'email/bulk:send' ],
  // The actions it is allowed to publish/start tasks for.
  // Here is can mail:send, and it can do everything under geocode,
  // such as weather:forecast, weather/metno:forecast
  // NOT IMPLEMENTED YET.
  pubPermissions: [ 'email:send', 'weather' ],
  // Specify how many connections of this client is allowed.
  // NOT IMPLEMENTED YET.
  maxConnections: 1
});

hub.start(); // Open for business

Client

import { Client } from 'taskhub';

const client = new Client({
  url: 'ws:server:port', // server url
  clientName: 'emailer', // unique name
  key: '---super-secret-key---'
});

client.sub('email/bulk:send', async (task) => {
  // Tell the hub this service will begin work on this task, so that it knows to wait.
  // Otherwise, the hub will assume a task is complete when all listening services has seen it, or timedout. (The timeout is short.)
  task.start();

  // Get payload (async because it could be large)
  const data = await task.getPayload();

  // Update the caller on current progress
  task.update(data);

  // Triggers when another client updates the task
  task.on('update', (task) => { task.getLastUpdate() });

  // When another client returns and thereby completes the task globally.
  task.on('success', () => {});

  // Done and the data is sent to the caller/publisher.
  return data; // or task.success(result);

  // This client has completed but doesn't want to return a result to pub.
  task.drop();
});

// Calling
try {
  let result = await client.pub('email/bulk:send', emails).getResult();
} catch(err) { }

// Call it with value if error, to avoid the exceptions, and wait 30 min
let result = await client.pub('email/bulk:send', emails, 1000 * 60 * 30 /* 30 min */)
  .getResult(valueIfError);

// Call it with progress updates
let finalResult = await client.pub('email/bulk:send', emails)
  .on('update', (task) => { console.log(task.getLastUpdate()); })
  .getResult(valueIfError);