RedisHashStore

RedisHashStore extends ActiveSupport's RedisCacheStore to provide the ability to easily use Redis hashes for caching.

We decided to create this gem because:

1. We were previously using #delete_matched which can have many performance issues at scale (See this similar issue at GitLab).
2. #deleted_matched doesn't delete values from all the nodes in a Redis cluster.

Rails

Supported Rails versions are listed in Appraisals.

Installing

Install it yourself as:

$ gem install redis_hash_store

Or add it to your Gemfile:

gem 'redis_hash_store'

and then execute:

$ bundle

Configuration

All you need to do is add:

# config/production(development|test|staging|preview).rb

config.cache_store = :redis_hash_store, redis_cache_store_options

Usage

This gem simply adds new functionality to RedisCacheStore, so all existing logic in that class is not affected.

Here is a list of available methods:

• #write_hash_value
• #read_hash_value
• #read_hash
• #delete_hash_value
• #delete_hash
• #fetch_hash_value

Examples

Let's imagine we need to store amount of Services for City.

#write_hash_value

city = "Riyadh"
coffee_shop_type = "coffee_shop"
restaurants_type = "restaurant"

coffee_shops_count = Service.where(type: coffee_shop_type, city: city).count
=> 250
restaurants_count = Service.where(type: restaurants_type, city: city).count
=> 340

Rails.cache.write_hash_value("#{city} counters", coffee_shop_type, coffee_shops_count)
=> 1
Rails.cache.write_hash_value("#{city} counters", restaurants_type, restaurants_count)
=> 1

#read_hash_value

Now it's accessible by:

Rails.cache.read_hash_value("#{city} counters", coffee_shop_type)
=> 250
Rails.cache.read_hash_value("#{city} counters", restaurants_type)
=> 340

#read_hash

Looks pretty easy, right? Maybe you're thinking: "What the difference?"

1. You can access all records under the "#{city} counters" hash

Rails.cache.read_hash("#{city} counters")
=> { "coffee_shop"=>250, "restaurant"=>340 }

#delete_hash_value

2. You can easily remove every value under "#{city} counters"

Rails.cache.delete_hash_value("#{city} counters", coffee_shop_type)
=> 1

#delete_hash

3. You can also delete the entire "#{city} counters" hash

Rails.cache.delete_hash("#{city} counters")
=> 1

#fetch_hash_value

4. You can fetch needed value under "#{city} counters"

Rails.cache.fetch_hash_value("#{city} counters", coffee_shop_type) do
  Service.where(type: coffee_shop_type, city: city).count
end
=> 250

Rails.cache.fetch_hash_value("#{city} counters", coffee_shop_type, force: true) do
  Service.where(type: coffee_shop_type, city: city).count * 2
end
=> 500

Benchmarks

indexes = 1..1_000_000

indexes.each do |index|
  Rails.cache.write("some_data_#{index}", index)
  Rails.cache.write_hash_value("some_data", index, index)
end

Benchmark.bm do |x|
  x.report("delete_matched")  { Rails.cache.delete_matched("some_data_*") }
  x.report("delete_hash")     { Rails.cache.delete_hash("some_data") }
end

    user         system      total        real
delete_matched  0.571040   0.244962   0.816002 (3.791056)
delete_hash     0.000000   0.000225   0.000225 (0.677891)

Contributing

Please see CONTRIBUTING.md.