> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fly.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Sidekiq Background Workers

Rails applications commonly defer complex tasks that take a long to complete to a background worker to make web responses seem fast. This guide shows how to use [Sidekiq](https://github.com/mperham/sidekiq), a popular open-source Rails background job framework, to set up background workers, but it could be done with other great libraries like [Good Job](https://github.com/bensheldon/good_job), [Resque](https://github.com/resque/resque), [etc](https://www.ruby-toolbox.com/categories/Background_Jobs).

## Provision a Redis server

Sidekiq depends on Redis to communicate between the Rails server process and the background workers. Follow the [Redis setup guide](/upstash/redis) to provision a Redis server and set a `REDIS_URL` within the Rails app. Be sure to set the `REDIS_URL` via a secret as demonstrated [here](/rails/the-basics/configuration#secret-variables).

Verify the `REDIS_URL` is available to your Rails application before you continue by running:

<CodeGroup>
  ```bash cmd theme={null}
  fly ssh console -C "printenv REDIS_URL"
  ```

  ```output output theme={null}
  REDIS_URL=redis://default:yoursecretpassword@my-apps-redis-host.internal:6379
  ```
</CodeGroup>

If you don't see `REDIS_URL` in the command above, Sidekiq won't be able to connect and process background jobs.

## Run multiple processes

Most production Rails applications run background workers in a separate process. There's a few ways of accomplishing that on Fly that are [outlined in the multiple-processes](/app-guides/multiple-processes) docs.

The quickest way to run multiple processes in one region is via the `processes` directive in the `fly.toml` file.

<Info>
  The `[processes]` directive currently only works within a single Fly region. [Scaling a Rails application to multiple regions](/rails/advanced-guides/multi-region) requires a different approach to running multiple processes.
</Info>

Add the following to the `fly.toml`:

```toml theme={null}
[processes]
app = "bin/rails server"
worker = "bundle exec sidekiq"
```

Then under the `[http_service]` directive, add `processes = ["app"]`. The configuration file should look something like this:

```toml theme={null}
[http_service]
  processes = ["app"] # this service only applies to the app process
  internal_port = 3000
  force_https = true
  auto_stop_machines = true
  auto_start_machines = true
  min_machines_running = 0
```

This associates the process with the service that Fly launches.

## Deploy and test

Once multiple processes are configured in the `fly.toml` file, deploy them via:

```bash theme={null}
fly deploy
```

If all goes well the application should launch with both `app` and `worker` processes. Be sure to run through the application and test features that kick-off background jobs. If you're having issues getting it working, run `fly logs` to see errors.

## Scaling

Scaling up and down processes may be accomplished by running:

```bash theme={null}
fly scale count app=3 worker=3
```

To view the current state of the application's scale, run:

<CodeGroup>
  ```bash cmd theme={null}
  fly status
  ```

  ```output output theme={null}
  App
    Name     = my-rails-app
    Owner    = personal
    Version  = 41
    Status   = running
    Hostname = my-rails-app.fly.dev

  Instances
  ID        PROCESS VERSION REGION  DESIRED STATUS  HEALTH CHECKS       RESTARTS  CREATED
  15088508  worker  41      ord     run     running                     0         34s ago
  8789ef49  app     41      ord     run     running 1 total, 1 passing  0         2022-07-26T16:06:34Z
  c419942b  app     41      ord     run     running 1 total, 1 passing  0         2022-07-26T16:05:52Z
  ea7af986  app     41      ord     run     running 1 total, 1 passing  0         2022-07-26T16:05:52Z
  d681c33d  worker  41      ord     run     running                     0         2022-07-26T15:42:30Z
  d8d8dc08  worker  41      ord     run     running                     0         2022-07-26T15:42:30Z
  ```
</CodeGroup>

In this case, we can see that 3 worker processes and 3 app processes are running in the `ord` region.