npm package: @operationalresults/faktory-worker
Description: A faktory worker framework for node apps
Author: Josh Bielick
Latest version: 4.6.0-1

# faktory-worker

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A node.js client and worker library for the [Faktory](https://github.com/contribsys/faktory) job server. The client allows you to push jobs and communicate with the Faktory server and the worker fetches background jobs from the Faktory server and processes them.

Faktory server compatibility: `~v1.6.1`

## Installation

```
npm install faktory-worker
```

## Links

- [API Docs](docs/api.md)
- [contribsys/faktory](https://github.com/contribsys/faktory)

## Usage

### Pushing jobs

```js
const faktory = require("faktory-worker");

(async () => {
  const client = await faktory.connect();
  await client.job("ResizeImage", { id: 333, size: "thumb" }).push();
  await client.close(); // reuse client if possible! remember to disconnect!
})().catch((e) => console.error(e));
```

A job is a payload of keys and values according to [the faktory job payload specification](https://github.com/contribsys/faktory/wiki/The-Job-Payload). Any keys provided will be passed to the faktory server during `PUSH`. A `jid` (uuid) is created automatically for your job when using this library. See [the spec](https://github.com/contribsys/faktory/wiki/The-Job-Payload) for more options and defaults.

### Pushing bulk jobs

```js
const faktory = require("faktory-worker");

(async () => {
  const client = await faktory.connect();
  let job1 = client.job("ResizeImage", { id: 333, size: "thumb" });
  let job2 = client.job("ResizeImage", { id: 334, size: "thumb" });

  let rejected = await client.pushBulk([job1, job2]);

  // rejected is a dictionary of [jid]: { payload, reason } if any failed to enqueue
  for (const [jid, { payload, reason }] of Object.entries(rejected)) {
    console.error(`Faild to push job for image ${payload.args[0].id}`);
  }

  await client.close(); // reuse client if possible! remember to disconnect!
})().catch((e) => console.error(e));
```

faktory link:
[https://github.com/contribsys/faktory/blob/main/Changes.md#160](url)

### Processing jobs

```js
const faktory = require("faktory-worker");

faktory.register("ResizeImage", async ({ id, size }) => {
  const image = await Image.find(id);
  await image.resize(size);
});

faktory.work().catch((error) => {
  console.error(`worker failed to start: ${error}`);
  process.exit(1);
});
```

A job function can be a sync or async function. Simply return a promise or use `await` in your async function to perform async tasks during your job. If you return early or don't `await` properly, the job will be `ACK`ed when the function returns.

`faktory.work()` traps `INT` and `TERM` signals so that it can gracefully shut down and finish any in-progress jobs before the `options.timeout` is reached.

#### Queues

By default, faktory_worker_node will listen to a `default` queue. If you'd like to use multiple queues, specify them in `options.queues` when instantiating a `Worker` or via `--queue` when using the CLI.

Queues can be specified in two ways: **strictly ordered** and **weighted random**.

##### Strictly Ordered

To specify queues to be worked on in a strict order (empty one, then the next, etc), use an array of queue names for `options.queues`.

```js
faktory.work({ queues: ["immediately", "afterwards"] });
```

In the previous example, all jobs are be fetched and started from the `immediately` queue before any are fetched and started from the `afterwards` queue.

##### Weighted Random

To specify queues to be worked on randomly, use an object of `[queueName: string]: number` entries. To ensure that some queues are processed more frequently than others, use a _higher_ weight number for that queue. Weights are relative. `100`, `200`, and `300` is no different than `1`, `2`, and `3`, respectively.

```js
faktory.work({ queues: { critical: 10, default: 1 } });
```

In the example above, the `critical` queue, weighted `10`, will have _roughly_ 10 jobs processed for every 1 job processed in the `default` queue. For equal weighting (just random queue processing), see below:

```js
faktory.work({ queues: { useast: 1, uswest: 1 } });
```

In the example above, `useast` and `uswest` have equal weights are worked on concurrently.

### Error Handling

A Faktory `Worker` emits several events that can be used to handle errors. When a job function throws an error, it is caught and the job is `FAIL`ed. You can listen for a `fail` event to do something with these errors (like send a message to an error aggregator).

An `error` event is emitted when an unexpected error occurs in the this library. If no listener is registered for the `error` event, a default handler is added.

```js
const worker = await faktory.work();

worker.on("fail", ({ job, error }) => {
  // report job error somewhere
});
```

### Middleware

Faktory middleware works just like [`koa`](https://github.com/koajs/koa) middleware. You can register a middleware function (async or sync) with `.use`. Middleware is called for every job that is performed. Always return a promise, `await next()`, or `return next();` to allow execution to continue down the middleware chain.

```js
const faktory = require("faktory-worker");

faktory.use(async (ctx, next) => {
  const start = process.hrtime();
  await next();
  const time = process.hrtime(start);
  console.info("%s took %ds %dms", ctx.job.jobtype, time[0], time[1] / 1e6);
});

faktory.work();
```

### CLI

`faktory-worker` comes with two helper scripts:

`node_modules/.bin/faktory-work`

Starts one worker. Use `--help` for more information.

and

`node_modules/.bin/faktory-cluster`

### Worker Options

You can override the default options for a faktory worker by providing an object to the `faktory.work()` method or the `Worker()` constructor.

Here are the defaults:

```js
await faktory.work({
  host: process.env.FAKTORY_URL || "127.0.0.1",

  // default: 7419 -- can extracted from FAKTORY_URL env var
  port: 7419,

  // can extracted from FAKTORY_URL env var
  password: undefined,

  // this is a max number of jobs the worker will have
  // in progress at any time
  concurrency: 20,

  // the queues the worker will process—remember to preserve default if overriding this
  // default fetching behavior is **Strictly Ordered**
  queues: ["default"],

  // the number of milliseconds jobs have to complete after
  // receiving a graceful shutdown signal. After this timeout, in-progress jobs may be abruptly stopped.
  timeout: 8 * 1000,

  // the worker id to use in the faktory-server connection
  // for this process. must be unique per process.
  wid: uuid().first(8),

  // labels for the faktory worker process to see in the UI
  labels: [],
});
```

### Debugging

Use `DEBUG=faktory*` to see related debug log lines.

## FAQ

- How do I specify the Faktory server location?

By default, it will connect to `tcp://127.0.0.1:7419`.
Use FAKTORY_URL to specify the URL, e.g. `tcp://faktory.example.com:12345` or use FAKTORY_PROVIDER to specify the environment variable which contains the URL: `FAKTORY_PROVIDER=FAKTORYTOGO_URL`. This level of
indirection is useful for SaaSes, Heroku Addons, etc.

- How do I access the job payload in my function?

The function passed to `register` can be a thunk. The registered function will receive the job `args` and if that function returns a function, that returned function will be called and provided the execution context (`ctx`) which contains the raw `job` payload at `ctx.job`, containing all custom props and other metadata of the job payload.

```js
faktory.register("JobWithHeaders", (...args) => async ({ job }) => {
  const [email] = args;
  I18n.locale = job.custom.locale;
  log(job.custom.txid);
  await sendEmail(email);
});
```

- How do I add middleware to the job execution stack?

Because many jobs may share the same dependencies, the faktory job processor holds a middleware stack of functions that will execute _before_ the job function does. You can add middleware to this stack by calling `faktory.use` and providing a function to be called. The middleware execution in faktory-worker works exactly the same as [`koa`](https://github.com/koajs/koa).

Here's an example of passing a pooled connection to every faktory job that's executed.

```js
const { createPool } = require("generic-pool"); // any pool or connection library works
const faktory = require("faktory");

const pool = createPool({
  create() {
    return new Client();
  },
  destroy(client) {
    return client.disconnect();
  },
});

faktory.use(async (ctx, next) => {
  ctx.db = await pool.acquire();
  try {
    // middleware *must* return next() or await next()
    // this invokes the downstream middleware (including your job fn)
    await next();
  } finally {
    // return connection to pool
    pool.release(ctx.db);
  }
});

faktory.register("TouchRecord", (id) => async ({ db }) => {
  const record = await db.find(id);
  await record.touch();
});
```

## Features

- [ ] Customizable logger
- [ ] Pro features
- [x] CLI: Require jobs from folder and automatically register
- [x] Mutate API
- [x] Connection pooling
- [x] Handle signals from server heartbeat response
- [x] Middleware
- [x] CLI
- [x] Heartbeat
- [x] Tests
- [x] Authentication
- [x] Fail jobs
- [x] Add'l client commands API
- [x] Labels

## Development

Install docker.

`bin/server` will run the faktory server in a docker container. The server is available at `127.0.0.1:7419`

## Debugging

Use `DEBUG=faktory*` to see debug output from this library.

## Tests

A faktory server must be running locally. Use `bin/server` to start one.

The tests can be run via `npm test`—they will be executed by ava.

## Author

Josh Bielick, @jbielick