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# Slowpoke
[Rack::Timeout](https://github.com/heroku/rack-timeout) enhancements for Rails
- safer service timeouts
- dynamic timeouts
- custom error pages
## Installation
Add this line to your application’s Gemfile:
```ruby
gem 'slowpoke'
```
And run:
```sh
rails generate slowpoke:install
```
This creates a `public/503.html` you can customize.
## Development
To try out custom error pages in development, temporarily add to `config/environments/development.rb`:
```ruby
config.slowpoke.timeout = 1
config.consider_all_requests_local = false
```
And add a `sleep` call to one of your actions:
```ruby
sleep(2)
```
The custom error page should appear.
## Production
The default timeout is 15 seconds. You can change this in `config/environments/production.rb` with:
```ruby
config.slowpoke.timeout = 5
```
For dynamic timeouts, use:
```ruby
config.slowpoke.timeout = lambda do |env|
request = Rack::Request.new(env)
request.path.start_with?("/admin") ? 15 : 5
end
```
Subscribe to timeouts with:
```ruby
ActiveSupport::Notifications.subscribe "timeout.slowpoke" do |name, start, finish, id, payload|
# report timeout
end
```
To learn more, see the [Rack::Timeout documentation](https://github.com/heroku/rack-timeout).
## Safer Service Timeouts
Rack::Timeout can raise an exception at any point in the code, which can leave your app in an [unclean state](https://www.schneems.com/2017/02/21/the-oldest-bug-in-ruby-why-racktimeout-might-hose-your-server/). The safest way to recover from a request timeout is to spawn a new process. This is the default behavior for Slowpoke.
For threaded servers like Puma, this means killing all threads when any one of them times out. This can have a significant impact on performance.
You can customize this behavior with:
```ruby
Slowpoke.on_timeout do |env|
next if Rails.env.development? || Rails.env.test?
exception = env["action_dispatch.exception"]
if exception && exception.backtrace.first.include?("/active_record/")
Slowpoke.kill
end
end
```
Note: To access `env["action_dispatch.exception"]` in development, temporarily add to `config/environments/development.rb`:
```ruby
config.consider_all_requests_local = false
```
## Database Timeouts
It’s a good idea to set a [statement timeout](https://github.com/ankane/the-ultimate-guide-to-ruby-timeouts/#statement-timeouts-1) and a [connect timeout](https://github.com/ankane/the-ultimate-guide-to-ruby-timeouts/#activerecord). For Postgres, your `config/database.yml` should include something like:
```yml
production:
connect_timeout: 3 # sec
variables:
statement_timeout: 5s
```
## Upgrading
### 0.3.0
If you set the timeout with:
```ruby
Slowpoke.timeout = 5
```
Remove it and add to `config/environments/production.rb`:
```ruby
config.slowpoke.timeout = 5
```
If you use migration timeouts, check out [this guide](https://github.com/ankane/the-ultimate-guide-to-ruby-timeouts/#statement-timeouts-1) for how to configure them directly in `config/database.yml`.
### 0.1.0
`0.1.0` removes database timeouts, since Rails supports them by default. To restore the previous behavior, use:
```yaml
production:
variables:
statement_timeout: <%= Slowpoke.timeout * 1000 %>
```
## History
View the [changelog](https://github.com/ankane/slowpoke/blob/master/CHANGELOG.md)
## Contributing
Everyone is encouraged to help improve this project. Here are a few ways you can help:
- [Report bugs](https://github.com/ankane/slowpoke/issues)
- Fix bugs and [submit pull requests](https://github.com/ankane/slowpoke/pulls)
- Write, clarify, or fix documentation
- Suggest or add new features
To get started with development:
```sh
git clone https://github.com/ankane/slowpoke.git
cd slowpoke
bundle install
```
|
