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https://github.com/mezis/level2
Multiple caching levels for Rails. Kinda like your CPU's L1/L2 caches.
https://github.com/mezis/level2
activesupport cache gem ruby ruby-on-rails
Last synced: about 1 month ago
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Multiple caching levels for Rails. Kinda like your CPU's L1/L2 caches.
- Host: GitHub
- URL: https://github.com/mezis/level2
- Owner: mezis
- License: mit
- Created: 2016-06-06T15:32:42.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2023-07-26T13:53:03.000Z (over 1 year ago)
- Last Synced: 2024-04-24T19:48:13.624Z (7 months ago)
- Topics: activesupport, cache, gem, ruby, ruby-on-rails
- Language: Ruby
- Size: 27.3 KB
- Stars: 16
- Watchers: 3
- Forks: 8
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE.txt
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README
# Level2 [](https://travis-ci.org/mezis/level2) [](https://badge.fury.io/rb/level2)
A gem for tiered Rails caching.
This lets you "stack" Rails caches: you can use a smaller, faster cache for the
hotest cached items, and a larger, slower cache for more — mimicking how
microprocessors commonly have a small, ultrafast L1 cache and slower L2 and L3
caches.
A common idiom is to use Rails's
[`memory_store`](http://guides.rubyonrails.org/caching_with_rails.html#activesupport-cache-memorystore)
as the first level, and
[`mem_cache_store`](http://guides.rubyonrails.org/caching_with_rails.html#activesupport-cache-memcachestore)
or
[`redis_store`](https://github.com/redis-store/redis-store/wiki/Frameworks-Configuration)
as the second.
If your production setup has multiple Ruby processes per server, and some free
memory on servers, it can be more sensible to run one `mem_cache_store` per
server plus a shared one.
## Behaviour
- When reading a cache key, try reading from the first level first, then go down
the list: if a key is in L1 and L2, the value in L1 will be returned —
honouring expiry.
- Higher levels of cache are populated when reading: if a key is in L2 but not
L1, it will be added to L1.
- When writing a key, it is written to all levels.
## Installation
Add this line to your application's Gemfile:
```ruby
gem 'level2'
```
And then execute:
$ bundle
Or install it yourself as:
$ gem install level2
## Usage
Level2 is configured like any other Rails cache store. Its array of options are passed to
the same store lookup.
Example:
```ruby
# in config/application.rb
config.cache_store = :level2, {
L1: [ :memory_store, size: 32.megabytes ],
L2: [ :mem_cache_store, 'host1.example.org:11211' ]
}
```
From thereon,
- `Rails.cache.read` and `.fetch` will read from `L1` and fall back to `L2` if
the key is absent from `L1`.
- On L1 misses and L2 hits, L1 will be populated.
- `Rails.cache.write` and `.fetch` will write to both stores.
While discouraged, it is possible to write directly to a given cache level:
```ruby
Rails.cache.write('foo', 'bar', only: :L2)
```
This can be useful in cases where `L1` is a non-shared cache (e.g. in-memory
cache) and `L2` is shared (e.g. Redis, Memcached); and you want to keep the
ability to bust the cache manually.
## Notifications
Level2 enriches
[`ActiveSupport::Notifications`](http://edgeguides.rubyonrails.org/active_support_instrumentation.html#active-support).
Event payloads will include a `:level` field. On cache hits, this will indicate
where the hit comes from; on misses, or any other event, the field may be
present but the value is unspecified.
Example:
```ruby
# in an initializer
ActiveSupport::Notifications.subscribe 'cache_read.active_support' do |*args|
event = ActiveSupport::Notifications::Event.new(*args)
if event.payload[:hit]
Rails.logger.info "Hit from #{event.payload[:level]}"
end
end
```
## Development
After checking out the repo, run `bin/setup` to install dependencies. Then, run
`rake spec` to run the tests. You can also run `bin/console` for an interactive
prompt that will allow you to experiment.
To install this gem onto your local machine, run `bundle exec rake install`. To
release a new version, update the version number in `version.rb`, and then run
`bundle exec rake release`, which will create a git tag for the version, push
git commits and tags, and push the `.gem` file to
[rubygems.org](https://rubygems.org).
## Contributing
Bug reports and pull requests are welcome on GitHub at
https://github.com/mezis/level2.
## License
The gem is available as open source under the terms of the [MIT
License](http://opensource.org/licenses/MIT).