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104 lines
4.2 KiB
104 lines
4.2 KiB
# Better Errors [](https://rubygems.org/gems/better_errors) [](https://travis-ci.org/charliesome/better_errors) [](https://codeclimate.com/github/charliesome/better_errors)
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Better Errors replaces the standard Rails error page with a much better and more useful error page. It is also usable outside of Rails in any Rack app as Rack middleware.
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## Features
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* Full stack trace
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* Source code inspection for all stack frames (with highlighting)
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* Local and instance variable inspection
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* Live REPL on every stack frame
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## Installation
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Add this to your Gemfile:
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```ruby
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group :development do
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gem "better_errors"
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end
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```
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If you would like to use Better Errors' **advanced features** (REPL, local/instance variable inspection, pretty stack frame names), you need to add the [`binding_of_caller`](https://github.com/banister/binding_of_caller) gem by [@banisterfiend](http://twitter.com/banisterfiend) to your Gemfile:
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```ruby
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gem "binding_of_caller"
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```
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This is an optional dependency however, and Better Errors will work without it.
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_Note: If you discover that Better Errors isn't working - particularly after upgrading from version 0.5.0 or less - be sure to set `config.consider_all_requests_local = true` in `config/environments/development.rb`._
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## Security
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**NOTE:** It is *critical* you put better\_errors in the **development** section. **Do NOT run better_errors in production, or on Internet facing hosts.**
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You will notice that the only machine that gets the Better Errors page is localhost, which means you get the default error page if you are developing on a remote host (or a virtually remote host, such as a Vagrant box). Obviously, the REPL is not something you want to expose to the public, but there may also be other pieces of sensitive information available in the backtrace.
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To poke selective holes in this security mechanism, you can add a line like this to your startup (for example, on Rails it would be `config/environments/development.rb`)
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```ruby
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BetterErrors::Middleware.allow_ip! ENV['TRUSTED_IP'] if ENV['TRUSTED_IP']
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```
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Then run Rails like this:
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```shell
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TRUSTED_IP=66.68.96.220 rails s
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```
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Note that the `allow_ip!` is actually backed by a `Set`, so you can add more than one IP address or subnet.
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**Tip:** You can find your apparent IP by hitting the old error page's "Show env dump" and looking at "REMOTE_ADDR".
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**VirtualBox:** If you are using VirtualBox and are accessing the guest from your host's browser, you will need to use `allow_ip!` to see the error page.
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## Usage
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If you're using Rails, there's nothing else you need to do.
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If you're not using Rails, you need to insert `BetterErrors::Middleware` into your middleware stack, and optionally set `BetterErrors.application_root` if you'd like Better Errors to abbreviate filenames within your application.
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Here's an example using Sinatra:
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```ruby
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require "sinatra"
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require "better_errors"
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configure :development do
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use BetterErrors::Middleware
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BetterErrors.application_root = __dir__
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end
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get "/" do
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raise "oops"
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end
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```
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### Unicorn, Puma, and other multi-worker servers
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Better Errors works by leaving a lot of context in server process memory. If
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you're using a web server that runs multiple "workers" it's likely that a second
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request (as happens when you click on a stack frame) will hit a different
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worker. That worker won't have the necessary context in memory, and you'll see
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a `Session Expired` message.
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If this is the case for you, consider turning the number of workers to one (1)
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in `development`. Another option would be to use Webrick, Mongrel, Thin,
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or another single-process server as your `rails server`, when you are trying
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to troubleshoot an issue in development.
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## Get in touch!
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If you're using better_errors, I'd love to hear from you. Drop me a line and tell me what you think!
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## Contributing
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1. Fork it
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2. Create your feature branch (`git checkout -b my-new-feature`)
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3. Commit your changes (`git commit -am 'Add some feature'`)
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4. Push to the branch (`git push origin my-new-feature`)
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5. Create new Pull Request
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