---
title: "Caching in development environment in Rails 5"
description:
  "Rails 5 has added ability to enable cache in development environment without
  changing environment.rb file. This blog post discusses the feature."
canonical_url: "https://www.bigbinary.com/blog/caching-in-development-environment-in-rails5"
markdown_url: "https://www.bigbinary.com/blog/caching-in-development-environment-in-rails5.md"
---

# Caching in development environment in Rails 5

Rails 5 has added ability to enable cache in development environment without
changing environment.rb file. This blog post discusses the feature.

- Author: Mohit Natoo
- Published: January 25, 2016
- Categories: Rails 5, Rails

In Rails 4 if I'm doing work related to caching then first I need to turn
caching "on" by opening file `config/environments/development.rb` and changing
following line.

```ruby

config.action_controller.perform_caching = false

```

After changing the value from `false` to `true`, I need to restart the server.

This means that if I am testing caching behavior locally then every time I turn
caching "on" or "off" I need to restart the server.

## New command to create development cache in Rails 5

Rails 5 has introduced a new command to create development cache and help us
test how caching behaves in development mode. Here is the
[issue](https://github.com/rails/rails/issues/18875) and here is the
[pull request](https://github.com/rails/rails/pull/20961).

```plaintext
$ rails dev:cache
Development mode is now being cached.
```

Execution of the above command creates file `caching-dev.txt` in `tmp`
directory.

## How does it work?

In Rails 5 when a brand new Rails app is created then
`config/environments/development.rb` file will have the following snippet of
code.

```ruby

if Rails.root.join('tmp/caching-dev.txt').exist?
  config.action_controller.perform_caching = true
  config.static_cache_control = "public, max-age=172800"
  config.cache_store = :mem_cache_store
else
  config.action_controller.perform_caching = false
  config.cache_store = :null_store
end

```

In the above code we are checking if the file `tmp/caching-dev.txt` is present
and then use `:mem_cache_store` to enable caching only if the file is found.

Also, here is a snippet from the
[dev cache source code](https://github.com/rails/rails/blob/master/railties/lib/rails/commands/dev/dev_command.rb).

```ruby

def dev_cache
  if File.exist? 'tmp/caching-dev.txt'
    File.delete 'tmp/caching-dev.txt'
    puts 'Development mode is no longer being cached.'
  else
    FileUtils.touch 'tmp/caching-dev.txt'
    puts 'Development mode is now being cached.'
  end

  FileUtils.touch 'tmp/restart.txt'
end

```

## What is the advantage

The advantage is that we do not need to restart the server manually if we want
to turn caching "on" or "off". It is internally taken care by the `dev_cache`
method that is executed when `rails dev:cache` is executed. You can see in the
source code that `tmp/restart.txt` is being **touched**.

Please note that **this feature is not supported** by unicorn, thin and webrick.
My guess is that DHH wants this feature because his team uses pow and pow
restarts when `tmp/restart.txt` is touched. He also created an issue for
[spring to watch tmp/restart.txt](https://github.com/rails/rails/issues/18874)
long time back.

## Disabling development cache

Execute the same command that was used to enable caching. If caching was
previously enabled then it will be turned "off" now.

```plaintext

$ rails dev:cache
Development mode is no longer being cached.

```

## Links

- [Human page](https://www.bigbinary.com/blog/caching-in-development-environment-in-rails5)