# GoodJob

[![Gem Version](https://badge.fury.io/rb/good_job.svg)](https://rubygems.org/gems/good_job)
[![Test Status](https://github.com/bensheldon/good_job/workflows/Test/badge.svg)](https://github.com/bensheldon/good_job/actions)

GoodJob is a multithreaded, Postgres-based, ActiveJob backend for Ruby on Rails.

**Inspired by [Delayed::Job](https://github.com/collectiveidea/delayed_job) and [Que](https://github.com/que-rb/que), GoodJob is designed for maximum compatibility with Ruby on Rails, ActiveJob, and Postgres to be simple and performant for most workloads.**

- **Designed for ActiveJob.** Complete support for [async, queues, delays, priorities, timeouts, and retries](https://edgeguides.rubyonrails.org/active_job_basics.html) with near-zero configuration.
- **Built for Rails.** Fully adopts Ruby on Rails [threading and code execution guidelines](https://guides.rubyonrails.org/threading_and_code_execution.html) with [Concurrent::Ruby](https://github.com/ruby-concurrency/concurrent-ruby).
- **Backed by Postgres.** Relies upon Postgres integrity, session-level Advisory Locks to provide run-once safety and stay within the limits of `schema.rb`, and LISTEN/NOTIFY to reduce queuing latency.
- **For most workloads.** Targets full-stack teams, economy-minded solo developers, and applications that enqueue 1-million jobs/day and more.

For more of the story of GoodJob, read the [introductory blog post](https://island94.org/2020/07/introducing-goodjob-1-0).

<details markdown="1">
<summary><strong>📊 Comparison of GoodJob with other job queue backends (click to expand)</strong></summary>

|                 | Queues, priority, retries | Database                              | Concurrency       | Reliability/Integrity  | Latency                  |
|-----------------|---------------------------|---------------------------------------|-------------------|------------------------|--------------------------|
| **GoodJob**     | ✅ Yes                     | ✅ Postgres                            | ✅ Multithreaded   | ✅ ACID, Advisory Locks | ✅ Postgres LISTEN/NOTIFY |
| **Que**         | ✅ Yes                     | 🔶️ Postgres, requires  `structure.sql` | ✅ Multithreaded   | ✅ ACID, Advisory Locks | ✅ Postgres LISTEN/NOTIFY |
| **Delayed Job** | ✅ Yes                     | ✅ Postgres                            | 🔴 Single-threaded | ✅ ACID, record-based   | 🔶 Polling                |
| **Sidekiq**     | ✅ Yes                     | 🔴 Redis                               | ✅ Multithreaded   | 🔴 Crashes lose jobs    | ✅ Redis BRPOP            |
| **Sidekiq Pro** | ✅ Yes                     | 🔴 Redis                               | ✅ Multithreaded   | ✅ Redis RPOPLPUSH      | ✅ Redis RPOPLPUSH        |

</details>

## Table of contents

- [Set up](#set-up)
- [Compatibility](#compatibility)
- [Configuration](#configuration)
    - [Command-line options](#command-line-options)
        - [`good_job start`](#good_job-start)
        - [`good_job cleanup_preserved_jobs`](#good_job-cleanup_preserved_jobs)
    - [Configuration options](#configuration-options)
    - [Global options](#global-options)
    - [Dashboard](#dashboard)
    - [ActiveJob concurrency](#activejob-concurrency)
    - [Cron-style repeating/recurring jobs](#cron-style-repeatingrecurring-jobs)
    - [Updating](#updating)
        - [Upgrading minor versions](#upgrading-minor-versions)
        - [Upgrading v1 to v2](#upgrading-v1-to-v2)
- [Go deeper](#go-deeper)
    - [Exceptions, retries, and reliability](#exceptions-retries-and-reliability)
        - [Exceptions](#exceptions)
        - [Retries](#retries)
        - [ActionMailer retries](#actionmailer-retries)
    - [Timeouts](#timeouts)
    - [Optimize queues, threads, and processes](#optimize-queues-threads-and-processes)
    - [Database connections](#database-connections)
    - [Execute jobs async / in-process](#execute-jobs-async--in-process)
    - [Migrate to GoodJob from a different ActiveJob backend](#migrate-to-goodjob-from-a-different-activejob-backend)
    - [Monitor and preserve worked jobs](#monitor-and-preserve-worked-jobs)
    - [PgBouncer compatibility](#pgbouncer-compatibility)
- [Contribute](#contribute)
    - [Gem development](#gem-development)
    - [Release](#release)
- [License](#license)

## Set up

1. Add `good_job` to your application's Gemfile:

    ```ruby
    gem 'good_job'
    ```

1. Install the gem:

    ```bash
    $ bundle install
    ```

1. Run the GoodJob install generator. This will generate a database migration to create a table for GoodJob's job records:

    ```bash
    $ bin/rails g good_job:install
    ```

    Run the migration:

    ```bash
    $ bin/rails db:migrate
    ```

   Optional: If using Rails' multiple databases with the `migrations_paths` configuration option, use the `--database` option:

    ```bash
    bin/rails g good_job:install --database animals
    bin/rails db:migrate:animals
    ```

1. Configure the ActiveJob adapter:

    ```ruby
    # config/application.rb
    config.active_job.queue_adapter = :good_job
    ```

1. Inside of your application, queue your job 🎉:

    ```ruby
    YourJob.perform_later
    ```

    GoodJob supports all ActiveJob features:

    ```ruby
    YourJob.set(queue: :some_queue, wait: 5.minutes, priority: 10).perform_later
    ```

1. In development, GoodJob executes jobs immediately. In production, GoodJob provides different options:

    - By default, GoodJob separates job enqueuing from job execution so that jobs can be scaled independently of the web server.  Use the GoodJob command-line tool to execute jobs:

        ```bash
        $ bundle exec good_job start
        ```

        Ideally the command-line tool should be run on a separate machine or container from the web process. For example, on Heroku:

        ```Procfile
        web: rails server
        worker: bundle exec good_job start
        ```

        The command-line tool supports a variety of options, see the reference below for command-line configuration.

    - GoodJob can also be configured to execute jobs within the web server process to save on resources. This is useful for low-workloads when economy is paramount.

        ```
        $ GOOD_JOB_EXECUTION_MODE=async rails server
        ```

        Additional configuration is likely necessary, see the reference below for configuration.

## Compatibility

- **Ruby on Rails:** 5.2+
- **Ruby:** MRI 2.5+. JRuby 9.2.13+ (_JRuby's `activerecord-jdbcpostgresql-adapter` gem does not support Postgres LISTEN/NOTIFY)._
- **Postgres:** 9.6+

## Configuration

### Command-line options

There several top-level commands available through the `good_job` command-line tool.

Configuration options are available with `help`.

#### `good_job start`

`good_job start` executes queued jobs.

```bash
$ bundle exec good_job help start

Usage:
  good_job start

Options:
  [--max-threads=COUNT]        # Maximum number of threads to use for working jobs. (env var: GOOD_JOB_MAX_THREADS, default: 5)
  [--queues=QUEUE_LIST]        # Queues to work from. (env var: GOOD_JOB_QUEUES, default: *)
  [--poll-interval=SECONDS]    # Interval between polls for available jobs in seconds (env var: GOOD_JOB_POLL_INTERVAL, default: 1)
  [--max-cache=COUNT]          # Maximum number of scheduled jobs to cache in memory (env var: GOOD_JOB_MAX_CACHE, default: 10000)
  [--shutdown-timeout=SECONDS] # Number of seconds to wait for jobs to finish when shutting down before stopping the thread. (env var: GOOD_JOB_SHUTDOWN_TIMEOUT, default: -1 (forever))
  [--enable-cron]              # Whether to run cron process (default: false)
  [--daemonize]                # Run as a background daemon (default: false)
  [--pidfile=PIDFILE]          # Path to write daemonized Process ID (env var: GOOD_JOB_PIDFILE, default: tmp/pids/good_job.pid)

Executes queued jobs.

All options can be configured with environment variables.
See option descriptions for the matching environment variable name.

== Configuring queues

Separate multiple queues with commas; exclude queues with a leading minus;
separate isolated execution pools with semicolons and threads with colons.
```

#### `good_job cleanup_preserved_jobs`

`good_job cleanup_preserved_jobs` deletes preserved job records. See [`GoodJob.preserve_job_records` for when this command is useful.

```bash
$ bundle exec good_job help cleanup_preserved_jobs

Usage:
  good_job cleanup_preserved_jobs

Options:
  [--before-seconds-ago=SECONDS] # Delete records finished more than this many seconds ago (env var:  GOOD_JOB_CLEANUP_PRESERVED_JOBS_BEFORE_SECONDS_AGO, default: 86400)

Deletes preserved job records.

By default, GoodJob deletes job records when the job is performed and this
command is not necessary.

However, when `GoodJob.preserve_job_records = true`, the jobs will be
preserved in the database. This is useful when wanting to analyze or
inspect job performance.

If you are preserving job records this way, use this command regularly
to delete old records and preserve space in your database.
```

### Configuration options

To use GoodJob, you can set `config.active_job.queue_adapter` to a `:good_job`.

Additional configuration can be provided via `config.good_job.OPTION = ...` for example:

```ruby
# config/application.rb

config.active_job.queue_adapter = :good_job

# Configure options individually...
config.good_job.execution_mode = :async
config.good_job.max_threads = 5
config.good_job.poll_interval = 30 # seconds
config.good_job.shutdown_timeout = 25 # seconds
config.good_job.enable_cron = true
config.good_job.cron = { example: { cron: '0 * * * *', class: 'ExampleJob'  } }
config.good_job.queues = '*'

# ...or all at once.
config.good_job = {
  execution_mode: :async,
  max_threads: 5,
  poll_interval: 30,
  shutdown_timeout: 25,
  enable_cron: true,
  cron: {
    example: {
      cron: '0 * * * *',
      class: 'ExampleJob'
    },
  },
  queues: '*',
}
```

Available configuration options are:

- `execution_mode` (symbol) specifies how and where jobs should be executed. You can also set this with the environment variable `GOOD_JOB_EXECUTION_MODE`. It can be any one of:
    - `:inline` executes jobs immediately in whatever process queued them (usually the web server process). This should only be used in test and development environments.
    - `:external` causes the adapter to enqueue jobs, but not execute them. When using this option (the default for production environments), you’ll need to use the command-line tool to actually execute your jobs.
    - `:async` (or `:async_server`) executes jobs in separate threads within the Rails web server process (`bundle exec rails server`). It can be more economical for small workloads because you don’t need a separate machine or environment for running your jobs, but if your web server is under heavy load or your jobs require a lot of resources, you should choose `:external` instead.  When not in the Rails web server, jobs will execute in `:external` mode to ensure jobs are not executed within `rails console`, `rails db:migrate`, `rails assets:prepare`, etc.
    - `:async_all` executes jobs in separate threads in _any_ Rails process.
- `max_threads` (integer) sets the maximum number of threads to use when `execution_mode` is set to `:async`. You can also set this with the environment variable `GOOD_JOB_MAX_THREADS`.
- `queues` (string) determines which queues to execute jobs from when `execution_mode` is set to `:async`. See the description of `good_job start` for more details on the format of this string. You can also set this with the environment variable `GOOD_JOB_QUEUES`.
- `poll_interval` (integer) sets the number of seconds between polls for jobs when `execution_mode` is set to `:async`. You can also set this with the environment variable `GOOD_JOB_POLL_INTERVAL`.
- `max_cache` (integer) sets the maximum number of scheduled jobs that will be stored in memory to reduce execution latency when also polling for scheduled jobs. Caching 10,000 scheduled jobs uses approximately 20MB of memory. You can also set this with the environment variable `GOOD_JOB_MAX_CACHE`.
- `shutdown_timeout` (float) number of seconds to wait for jobs to finish when shutting down before stopping the thread. Defaults to forever: `-1`. You can also set this with the environment variable `GOOD_JOB_SHUTDOWN_TIMEOUT`.
- `enable_cron` (boolean) whether to run cron process. Defaults to `false`. You can also set this with the environment variable `GOOD_JOB_ENABLE_CRON`.
- `cron` (hash) cron configuration. Defaults to `{}`. You can also set this as a JSON string with the environment variable `GOOD_JOB_CRON`

By default, GoodJob configures the following execution modes per environment:

```ruby

# config/environments/development.rb
config.active_job.queue_adapter = :good_job
config.good_job.execution_mode = :async

# config/environments/test.rb
config.active_job.queue_adapter = :good_job
config.good_job.execution_mode = :inline

# config/environments/production.rb
config.active_job.queue_adapter = :good_job
config.good_job.execution_mode = :external
```

### Global options

Good Job’s general behavior can also be configured via several attributes directly on the `GoodJob` module:

- **`GoodJob.active_record_parent_class`** (string) The ActiveRecord parent class inherited by GoodJob's ActiveRecord model `GoodJob::Job` (defaults to `"ActiveRecord::Base"`). Configure this when using [multiple databases with ActiveRecord](https://guides.rubyonrails.org/active_record_multiple_databases.html) or when other custom configuration is necessary for the ActiveRecord model to connect to the Postgres database. _The value must be a String to avoid premature initialization of ActiveRecord._
- **`GoodJob.logger`** ([Rails Logger](https://api.rubyonrails.org/classes/ActiveSupport/Logger.html)) lets you set a custom logger for GoodJob. It should be an instance of a Rails `Logger`.
- **`GoodJob.preserve_job_records`** (boolean) keeps job records in your database even after jobs are completed. (Default: `false`)
- **`GoodJob.retry_on_unhandled_error`** (boolean) causes jobs to be re-queued and retried if they raise an instance of `StandardError`. Instances of `Exception`, like SIGINT, will *always* be retried, regardless of this attribute’s value. (Default: `true`)
- **`GoodJob.on_thread_error`** (proc, lambda, or callable) will be called when an Exception. It can be useful for logging errors to bug tracking services, like Sentry or Airbrake.

You’ll generally want to configure these in `config/initializers/good_job.rb`, like so:

```ruby
# config/initializers/good_job.rb
GoodJob.active_record_parent_class = "ApplicationRecord"
GoodJob.preserve_job_records = true
GoodJob.retry_on_unhandled_error = false
GoodJob.on_thread_error = -> (exception) { Raven.capture_exception(exception) }
```

### Dashboard

![Dashboard UI](https://github.com/bensheldon/good_job/raw/main/SCREENSHOT.png)

_🚧 GoodJob's dashboard is a work in progress. Please contribute ideas and code on [Github](https://github.com/bensheldon/good_job/issues)._

GoodJob includes a Dashboard as a mountable `Rails::Engine`.

1. Explicitly require the Engine code at the top of your `config/application.rb` file, immediately after Rails is required. This is necessary because the mountable engine is an optional feature of GoodJob.

    ```ruby
    # config/application.rb
    require_relative 'boot'

    require 'rails/all'
    require 'good_job/engine' # <= Add this line
    # ...
    ```

1. Mount the engine in your `config/routes.rb` file. The following will mount it at `http://example.com/good_job`.

    ```ruby
    # config/routes.rb
    # ...
    mount GoodJob::Engine => 'good_job'
    ```

    Because jobs can potentially contain sensitive information, you should authorize access. For example, using Devise's `authenticate` helper, that might look like:

    ```ruby
    # config/routes.rb
    # ...
    authenticate :user, ->(user) { user.admin? } do
      mount GoodJob::Engine => 'good_job'
    end
    ```

    Another option is using basic auth like this:

    ```ruby
    # config/initializers/good_job.rb
    GoodJob::Engine.middleware.use(Rack::Auth::Basic) do |username, password|
      ActiveSupport::SecurityUtils.secure_compare(Rails.application.credentials.good_job_username, username) &&
        ActiveSupport::SecurityUtils.secure_compare(Rails.application.credentials.good_job_password, password)
    end
    ```

### ActiveJob concurrency

GoodJob can extend ActiveJob to provide limits on concurrently running jobs, either at time of _enqueue_ or at _perform_. Limiting concurrency can help prevent duplicate, double or unecessary jobs from being enqueued, or race conditions when performing, for example when interacting with 3rd-party APIs.

**Note:** Limiting concurrency at _enqueue_ requires Rails 6.0+ because Rails 5.2 does not support `throw :abort` in ActiveJob callbacks.

```ruby
class MyJob < ApplicationJob
  include GoodJob::ActiveJobExtensions::Concurrency

  good_job_control_concurrency_with(
    # Maximum number of jobs with the concurrency key to be concurrently enqueued
    enqueue_limit: 2,

    # Maximum number of jobs with the concurrency key to be concurrently performed
    perform_limit: 1,

    # A unique key to be globally locked against.
    # Can be String or Lambda/Proc that is invoked in the context of the job.
    # Note: Arguments passed to #perform_later must be accessed through `arguments` method.
    key: -> { "Unique-#{arguments.first}" } #  MyJob.perform_later("Alice") => "Unique-Alice"
  )

  def perform(first_name)
    # do work
  end
end
```

When testing, the resulting concurrency key value can be inspected:

```ruby
job = MyJob.perform_later("Alice")
job.good_job_concurrency_key #=> "Unique-Alice"
```

### Cron-style repeating/recurring jobs

GoodJob can enqueue jobs on a recurring basis that can be used as a replacement for cron.

Cron-style jobs are run on every GoodJob process (e.g. CLI or `async` execution mode) when `config.good_job.enable_cron = true`; use GoodJob's [ActiveJob concurrency](#activejob-concurrency) extension to limit the number of jobs that are enqueued.

Cron-format is parsed by the [`fugit`](https://github.com/floraison/fugit) gem, which has support for seconds-level resolution (e.g. `* * * * * *`).

```ruby
# config/environments/application.rb or a specific environment e.g. production.rb

# Enable cron in this process; e.g. only run on the first Heroku worker process
config.good_job.enable_cron = ENV['DYNO'] == 'worker.1' # or `true` or via $GOOD_JOB_ENABLE_CRON

# Configure cron with a hash that has a unique key for each recurring job
config.good_job.cron = {
  # Every 15 minutes, enqueue `ExampleJob.set(priority: -10).perform_later(42, name: "Alice")`
  frequent_task: { # each recurring job must have a unique key
    cron: "*/15 * * * *", # cron-style scheduling format by fugit gem
    class: "ExampleJob", # reference the Job class with a string
    args: [42, { name: "Alice" }], # arguments to pass; can also be a proc e.g. `-> { { when: Time.now } }`
    set: { priority: -10 }, # additional ActiveJob properties; can also be a lambda/proc e.g. `-> { { priority: [1,2].sample } }`
    description: "Something helpful", # optional description that appears in Dashboard (coming soon!)
  },
  another_task: {
    cron: "0 0,12 * * *",
    class: "AnotherJob",
  },
  # etc.
}
```

### Updating

GoodJob follows semantic versioning, though updates may be encouraged through deprecation warnings in minor versions.

#### Upgrading minor versions

Upgrading between minor versions (e.g. v1.4 to v1.5) should not introduce breaking changes, but can introduce new deprecation warnings and database migration notices.

To perform upgrades to the GoodJob database tables:

1. Generate new database migration files:

    ```bash
    bin/rails g good_job:update
    ```

   Optional: If using Rails' multiple databases with the `migrations_paths` configuration option, use the `--database` option:

    ```bash
    $ bin/rails g good_job:update --database animals
    ```

1. Run the database migration locally

    ```bash
    bin/rails db:migrate
    ```

1. Commit the migration files and resulting `db/schema.rb` changes.
1. Deploy the code, run the migrations against the production database, and restart server/worker processes.

#### Upgrading v1 to v2

GoodJob v2 introduces a new Advisory Lock key format that is different than the v1 advisory lock key format; it's therefore necessary to perform a simple, but staged production upgrade. If you are already using `>= v1.12+` no other changes are necessary.

1. Upgrade your production environment to `v1.99.x` following the minor version upgrade process, including database migrations. `v1.99` is a transitional release that is safely compatible with both `v1.x` and `v2.0.0` because it uses both `v1`- and `v2`-formatted advisory locks.
1. Address any deprecation warnings generated by `v1.99`.
1. Upgrade your production environment to `v1.99.x` to `v2.0.x` again following the _minor_ upgrade process.

Notable changes:

- Renames `:async_server` execution mode to `:async`; renames prior `:async` execution mode to `:async_all`.
- Sets default Development environment's execution mode to `:async` with disabled polling.
- Excludes performing jobs from `enqueue_limit`'s count in `GoodJob::ActiveJobExtensions::Concurrency`.
- Triggers `GoodJob.on_thread_error` for unhandled ActiveJob exceptions.
- Renames `GoodJob.reperform_jobs_on_standard_error` accessor to `GoodJob.retry_on_unhandled_error`.
- Renames `GoodJob::Adapter.shutdown(wait:)` argument to `GoodJob::Adapter.shutdown(timeout:)`.
- Changes Advisory Lock key format from `good_jobs[ROW_ID]` to `good_jobs-[ACTIVE_JOB_ID]`.
- Expects presence of columns `good_jobs.active_job_id`, `good_jobs.concurrency_key`, `good_jobs.concurrency_key`, and `good_jobs.retried_good_job_id`.

## Go deeper

### Exceptions, retries, and reliability

GoodJob guarantees that a completely-performed job will run once and only once. GoodJob fully supports ActiveJob's built-in functionality for error handling, retries and timeouts.

#### Exceptions

ActiveJob provides [tools for rescuing and retrying exceptions](https://guides.rubyonrails.org/active_job_basics.html#exceptions), including `retry_on`, `discard_on`, `rescue_from` that will rescue exceptions before they get to GoodJob.

If errors do reach GoodJob, you can assign a callable to `GoodJob.on_thread_error` to be notified. For example, to log errors to an exception monitoring service like Sentry (or Bugsnag, Airbrake, Honeybadger, etc.):

```ruby
# config/initializers/good_job.rb
GoodJob.on_thread_error = -> (exception) { Raven.capture_exception(exception) }
```

#### Retries

By default, GoodJob will automatically and immediately retry a job when an exception is raised to GoodJob.

However, ActiveJob can be configured to retry an infinite number of times, with an exponential backoff. Using ActiveJob's `retry_on` prevents exceptions from reaching GoodJob:

```ruby
class ApplicationJob < ActiveJob::Base
  retry_on StandardError, wait: :exponentially_longer, attempts: Float::INFINITY
  # ...
end
```

When using `retry_on` with _a limited number of retries_, the final exception will not be rescued and will raise to GoodJob. GoodJob can be configured to discard un-handled exceptions instead of retrying them:

```ruby
# config/initializers/good_job.rb
GoodJob.retry_on_unhandled_error = false
```

Alternatively, pass a block to `retry_on` to handle the final exception instead of raising it to GoodJob:

```ruby
class ApplicationJob < ActiveJob::Base
  retry_on StandardError, attempts: 5 do |_job, _exception|
    # Log error, do nothing, etc.
  end
  # ...
end
```

When using `retry_on` with an infinite number of retries, exceptions will never be raised to GoodJob, which means `GoodJob.on_thread_error` will never be called. To report log or report exceptions to an exception monitoring service (e.g. Sentry, Bugsnag, Airbrake, Honeybadger, etc), create an explicit exception wrapper. For example:

```ruby
class ApplicationJob < ActiveJob::Base
  retry_on StandardError, wait: :exponentially_longer, attempts: Float::INFINITY

  retry_on SpecialError, attempts: 5 do |_job, exception|
    Raven.capture_exception(exception)
  end

  around_perform do |_job, block|
    block.call
  rescue StandardError => e
    Raven.capture_exception(e)
    raise
  end
  # ...
end
```

#### ActionMailer retries

Any configuration in `ApplicationJob` will have to be duplicated on `ActionMailer::MailDeliveryJob` (`ActionMailer::DeliveryJob` in Rails 5.2 or earlier) because ActionMailer uses a custom class, `ActionMailer::MailDeliveryJob`, which inherits from `ActiveJob::Base`,  rather than your applications `ApplicationJob`.

You can use an initializer to configure `ActionMailer::MailDeliveryJob`, for example:

```ruby
# config/initializers/good_job.rb
ActionMailer::MailDeliveryJob.retry_on StandardError, wait: :exponentially_longer, attempts: Float::INFINITY

# With Sentry (or Bugsnag, Airbrake, Honeybadger, etc.)
ActionMailer::MailDeliveryJob.around_perform do |_job, block|
  block.call
rescue StandardError => e
  Raven.capture_exception(e)
  raise
end
```

Note, that `ActionMailer::MailDeliveryJob` is a default since Rails 6.0. Be sure that your app is using that class, as it
might also be configured to use (deprecated now) `ActionMailer::DeliveryJob`.

### Timeouts

Job timeouts can be configured with an `around_perform`:

```ruby
class ApplicationJob < ActiveJob::Base
  JobTimeoutError = Class.new(StandardError)

  around_perform do |_job, block|
    # Timeout jobs after 10 minutes
    Timeout.timeout(10.minutes, JobTimeoutError) do
      block.call
    end
  end
end
```

### Optimize queues, threads, and processes

By default, GoodJob creates a single thread execution pool that will execute jobs from any queue. Depending on your application's workload, job types, and service level objectives, you may wish to optimize execution resources. For example, providing dedicated execution resources for transactional emails so they are not delayed by long-running batch jobs. Some options:

- Multiple execution pools within a single process:

    ```bash
    $ bundle exec good_job --queues="transactional_messages:2;batch_processing:1;-transactional_messages,batch_processing:2;*" --max-threads=5
    ```

    This configuration will result in a single process with 4 isolated thread execution pools. Isolated execution pools are separated with a semicolon (`;`) and queue names and thread counts with a colon (`:`)

    - `transactional_messages:2`: execute jobs enqueued on `transactional_messages` with up to 2 threads.
    - `batch_processing:1` execute jobs enqueued on `batch_processing` with a single thread.
    - `-transactional_messages,batch_processing`: execute jobs enqueued on _any_ queue _excluding_ `transactional_messages` or `batch_processing` with up to 2 threads.
    - `*`: execute jobs on any queue on up to 5 threads, as configured by `--max-threads=5`

    For moderate workloads, multiple isolated thread execution pools offers a good balance between congestion management and economy.

    Configuration can be injected by environment variables too:

    ```bash
    $ GOOD_JOB_QUEUES="transactional_messages:2;batch_processing:1;-transactional_messages,batch_processing:2;*" GOOD_JOB_MAX_THREADS=5 bundle exec good_job
    ```

- Multiple processes; for example, on Heroku:

    ```procfile
    # Procfile

    # Separate dyno types
    worker: bundle exec good_job --max-threads=5
    transactional_worker: bundle exec good_job --queues="transactional_messages" --max-threads=2
    batch_worker: bundle exec good_job --queues="batch_processing" --max-threads=1

    # Combined multi-process dyno
    combined_worker: bundle exec good_job --max-threads=5 & bundle exec good_job --queues="transactional_messages" --max-threads=2 & bundle exec good_job --queues="batch_processing" --max-threads=1 & wait -n
    ```

    Running multiple processes can optimize for CPU performance at the expense of greater memory and system resource usage.

Keep in mind, queue operations and management is an advanced discipline. This stuff is complex, especially for heavy workloads and unique processing requirements. Good job 👍

### Database connections

Each GoodJob execution thread requires its own database connection that is automatically checked out from Rails’ connection pool. _Allowing GoodJob to create more threads than available database connections can lead to timeouts and is not recommended._ For example:

```yaml
# config/database.yml
pool: <%= [ENV.fetch("RAILS_MAX_THREADS", 5).to_i, ENV.fetch("GOOD_JOB_MAX_THREADS", 4).to_i].max %>
```

### Execute jobs async / in-process

GoodJob can execute jobs "async" in the same process as the web server (e.g. `bin/rails s`). GoodJob's async execution mode offers benefits of economy by not requiring a separate job worker process, but with the tradeoff of increased complexity. Async mode can be configured in two ways:

- Via Rails configuration:

    ```ruby
    # config/environments/production.rb
    config.active_job.queue_adapter = :good_job

    # To change the execution mode
    config.good_job.execution_mode = :async

    # Or with more configuration
    config.good_job = {
      execution_mode: :async,
      max_threads: 4,
      poll_interval: 30
    }
    ```

- Or, with environment variables:

    ```bash
    $ GOOD_JOB_EXECUTION_MODE=async GOOD_JOB_MAX_THREADS=4 GOOD_JOB_POLL_INTERVAL=30 bin/rails server
    ```

Depending on your application configuration, you may need to take additional steps:

- Ensure that you have enough database connections for both web and job execution threads:

    ```yaml
    # config/database.yml
    pool: <%= ENV.fetch("RAILS_MAX_THREADS", 5).to_i + ENV.fetch("GOOD_JOB_MAX_THREADS", 4).to_i %>
    ```

- When running Puma with workers (`WEB_CONCURRENCY > 0`) or another process-forking web server, GoodJob's threadpool schedulers should be stopped before forking, restarted after fork, and cleanly shut down on exit. Stopping GoodJob's scheduler pre-fork is recommended to ensure that GoodJob does not continue executing jobs in the parent/controller process. For example, with Puma:

    ```ruby
    # config/puma.rb

    before_fork do
      GoodJob.shutdown
    end

    on_worker_boot do
      GoodJob.restart
    end

    on_worker_shutdown do
      GoodJob.shutdown
    end

    MAIN_PID = Process.pid
    at_exit do
      GoodJob.shutdown if Process.pid == MAIN_PID
    end
    ```

  GoodJob is compatible with Puma's `preload_app!` method.

### Migrate to GoodJob from a different ActiveJob backend

If your application is already using an ActiveJob backend, you will need to install GoodJob to enqueue and perform newly created jobs _and_ finish performing pre-existing jobs on the previous backend.

1. Enqueue newly created jobs on GoodJob either entirely by setting `ActiveJob::Base.queue_adapter = :good_job` or progressively via individual job classes:

    ```ruby
    # jobs/specific_job.rb
    class SpecificJob < ApplicationJob
      self.queue_adapter = :good_job
      # ...
    end
    ```

1. Continue running executors for both backends. For example, on Heroku it's possible to run [two processes](https://help.heroku.com/CTFS2TJK/how-do-i-run-multiple-processes-on-a-dyno) within the same dyno:

   ```procfile
    # Procfile
    # ...
    worker: bundle exec que ./config/environment.rb & bundle exec good_job & wait -n
    ```

1. Once you are confident that no unperformed jobs remain in the previous ActiveJob backend, code and configuration for that backend can be completely removed.

### Monitor and preserve worked jobs

GoodJob is fully instrumented with [`ActiveSupport::Notifications`](https://edgeguides.rubyonrails.org/active_support_instrumentation.html#introduction-to-instrumentation).

By default, GoodJob will delete job records after they are run, regardless of whether they succeed or not (raising a kind of `StandardError`), unless they are interrupted (raising a kind of `Exception`).

To preserve job records for later inspection, set an initializer:

```ruby
# config/initializers/good_job.rb
GoodJob.preserve_job_records = true
```

It is also necessary to delete these preserved jobs from the database after a certain time period:

- For example, in a Rake task:

    ```ruby
    GoodJob::Job.finished(1.day.ago).delete_all
    ```

- For example, using the `good_job` command-line utility:

    ```bash
    $ bundle exec good_job cleanup_preserved_jobs --before-seconds-ago=86400
    ```

### PgBouncer compatibility

GoodJob is not compatible with PgBouncer in _transaction_ mode, but is compatible with PgBouncer's _connection_ mode. GoodJob uses connection-based advisory locks and LISTEN/NOTIFY, both of which require full database connections.

A workaround to this limitation is to make a direct database connection available to GoodJob. With Rails 6.0's support for [multiple databases](https://guides.rubyonrails.org/active_record_multiple_databases.html), a direct connection to the database can be configured:

1. Define a direct connection to your database that is not proxied through PgBouncer, for example:

    ```yml
    # config/database.yml

    production:
      primary:
        url: postgres://pgbouncer_host/my_database
      primary_direct:
        url: postgres://database_host/my_database
    ```

1. Create a new ActiveRecord base class that uses the direct database connection

    ```ruby
    # app/models/application_direct_record.rb

    class ApplicationDirectRecord < ActiveRecord::Base
      self.abstract_class = true
      connects_to database: :primary_direct
    end
    ```

1. Configure GoodJob to use the newly created ActiveRecord base class:

    ```ruby
    # config/initializers/good_job.rb

    GoodJob.active_record_parent_class = "ApplicationDirectRecord"
    ```

## Contribute

Contributions are welcomed and appreciated 🙏

- Review the [Prioritized Project Backlog](https://github.com/bensheldon/good_job/projects/1).
- Open a new Issue or contribute to an [existing Issue](https://github.com/bensheldon/good_job/issues). Questions or suggestions are fantastic.
- Participate according to our [Code of Conduct](https://github.com/bensheldon/good_job/projects/1).

### Gem development

To run tests:

```bash
# Clone the repository locally
$ git clone git@github.com:bensheldon/good_job.git

# Set up the local environment
$ bin/setup

# Run the tests
$ bin/rspec
```

This gem uses Appraisal to run tests against multiple versions of Rails:

```bash
# Install Appraisal(s) gemfiles
$ bundle exec appraisal

# Run tests
$ bundle exec appraisal bin/rspec
```

For developing locally within another Ruby on Rails project:

```bash
# Within Ruby on Rails directory...
$ bundle config local.good_job /path/to/local/git/repository

# Confirm that the local copy is used
$ bundle install

# => Using good_job 0.1.0 from https://github.com/bensheldon/good_job.git (at /Users/You/Projects/good_job@dc57fb0)
```

### Release

Package maintainers can release this gem by running:

```bash
# Sign into rubygems
$ gem signin

# Add a .env file with the following:
# CHANGELOG_GITHUB_TOKEN= # Github Personal Access Token

# Update version number, changelog, and create git commit:
$ bundle exec rake release[minor] # major,minor,patch

# ..and follow subsequent directions.
```

## License

The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).