Class: ActiveSupport::Cache::RedisCacheStore

Inherits:
Store show all
Defined in:
activesupport/lib/active_support/cache/redis_cache_store.rb

Overview

Redis cache store.

Deployment note: Take care to use a *dedicated Redis cache* rather than pointing this at your existing Redis server. It won't cope well with mixed usage patterns and it won't expire cache entries by default.

Redis cache server setup guide: redis.io/topics/lru-cache

  • Supports vanilla Redis, hiredis, and Redis::Distributed.

  • Supports Memcached-like sharding across Redises with Redis::Distributed.

  • Fault tolerant. If the Redis server is unavailable, no exceptions are raised. Cache fetches are all misses and writes are dropped.

  • Local cache. Hot in-memory primary cache within block/middleware scope.

  • read_multi and write_multi support for Redis mget/mset. Use Redis::Distributed 4.0.1+ for distributed mget support.

  • delete_matched support for Redis KEYS globs.

Defined Under Namespace

Modules: LocalCacheWithRaw

Constant Summary collapse

MAX_KEY_BYTESIZE =

Keys are truncated with their own SHA2 digest if they exceed 1kB

1024
DEFAULT_REDIS_OPTIONS = 
{
  connect_timeout:    20,
  read_timeout:       1,
  write_timeout:      1,
  reconnect_attempts: 0,
}
DEFAULT_ERROR_HANDLER = 
-> (method:, returning:, exception:) do
  if logger
    logger.error { "RedisCacheStore: #{method} failed, returned #{returning.inspect}: #{exception.class}: #{exception.message}" }
  end
end

Instance Attribute Summary collapse

Attributes inherited from Store

#options, #silence

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Store

#delete, #delete_multi, #exist?, #fetch, #fetch_multi, #mute, #read, #silence!, #write, #write_multi

Constructor Details

#initialize(namespace: nil, compress: true, compress_threshold: 1.kilobyte, expires_in: nil, race_condition_ttl: nil, error_handler: DEFAULT_ERROR_HANDLER, **redis_options) ⇒ RedisCacheStore

Creates a new Redis cache store.

Handles four options: :redis block, :redis instance, single :url string, and multiple :url strings.

Option  Class       Result
:redis  Proc    ->  options[:redis].call
:redis  Object  ->  options[:redis]
:url    String  ->  Redis.new(url: …)
:url    Array   ->  Redis::Distributed.new([{ url: … }, { url: … }, …])

No namespace is set by default. Provide one if the Redis cache server is shared with other apps: namespace: 'myapp-cache'.

Compression is enabled by default with a 1kB threshold, so cached values larger than 1kB are automatically compressed. Disable by passing compress: false or change the threshold by passing compress_threshold: 4.kilobytes.

No expiry is set on cache entries by default. Redis is expected to be configured with an eviction policy that automatically deletes least-recently or -frequently used keys when it reaches max memory. See redis.io/topics/lru-cache for cache server setup.

Race condition TTL is not set by default. This can be used to avoid “thundering herd” cache writes when hot cache entries are expired. See ActiveSupport::Cache::Store#fetch for more.


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 180

def initialize(namespace: nil, compress: true, compress_threshold: 1.kilobyte, expires_in: nil, race_condition_ttl: nil, error_handler: DEFAULT_ERROR_HANDLER, **redis_options)
  @redis_options = redis_options

  @max_key_bytesize = MAX_KEY_BYTESIZE
  @error_handler = error_handler

  super namespace: namespace,
    compress: compress, compress_threshold: compress_threshold,
    expires_in: expires_in, race_condition_ttl: race_condition_ttl
end

Instance Attribute Details

#max_key_bytesize ⇒ Object (readonly)

Returns the value of attribute max_key_bytesize


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 151

def max_key_bytesize
  @max_key_bytesize
end

#redis_options ⇒ Object (readonly)

Returns the value of attribute redis_options


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 150

def redis_options
  @redis_options
end

Class Method Details

.build_redis(redis: nil, url: nil, **redis_options) ⇒ Object

Factory method to create a new Redis instance.

Handles four options: :redis block, :redis instance, single :url string, and multiple :url strings.

Option  Class       Result
:redis  Proc    ->  options[:redis].call
:redis  Object  ->  options[:redis]
:url    String  ->  Redis.new(url: …)
:url    Array   ->  Redis::Distributed.new([{ url: … }, { url: … }, …])


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 124

def build_redis(redis: nil, url: nil, **redis_options) #:nodoc:
  urls = Array(url)

  if redis.is_a?(Proc)
    redis.call
  elsif redis
    redis
  elsif urls.size > 1
    build_redis_distributed_client urls: urls, **redis_options
  else
    build_redis_client url: urls.first, **redis_options
  end
end

.supports_cache_versioning? ⇒ Boolean

Advertise cache versioning support.

Returns:

  • (Boolean) 

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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 70

def self.supports_cache_versioning?
  true
end

Instance Method Details

#cleanup(options = nil) ⇒ Object

Cache Store API implementation.

Removes expired entries. Handled natively by Redis least-recently-/ least-frequently-used expiry, so manual cleanup is not supported.


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 311

def cleanup(options = nil)
  super
end

#clear(options = nil) ⇒ Object

Clear the entire cache on all Redis servers. Safe to use on shared servers if the cache is namespaced.

Failsafe: Raises errors.


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 319

def clear(options = nil)
  failsafe :clear do
    if namespace = merged_options(options)[:namespace]
      delete_matched "*", namespace: namespace
    else
      redis.with { |c| c.flushdb }
    end
  end
end

#decrement(name, amount = 1, options = nil) ⇒ Object

Cache Store API implementation.

Decrement a cached value. This method uses the Redis decr atomic operator and can only be used on values written with the :raw option. Calling it on a value not stored with :raw will initialize that value to zero.

Failsafe: Raises errors.


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 292

def decrement(name, amount = 1, options = nil)
  instrument :decrement, name, amount: amount do
    failsafe :decrement do
      options = merged_options(options)
      key = normalize_key(name, options)

      redis.with do |c|
        c.decrby(key, amount).tap do
          write_key_expiry(c, key, options)
        end
      end
    end
  end
end

#delete_matched(matcher, options = nil) ⇒ Object

Cache Store API implementation.

Supports Redis KEYS glob patterns:

h?llo matches hello, hallo and hxllo
h*llo matches hllo and heeeello
h[ae]llo matches hello and hallo, but not hillo
h[^e]llo matches hallo, hbllo, ... but not hello
h[a-b]llo matches hallo and hbllo

Use \ to escape special characters if you want to match them verbatim.

See redis.io/commands/KEYS for more.

Failsafe: Raises errors.


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 240

def delete_matched(matcher, options = nil)
  instrument :delete_matched, matcher do
    unless String === matcher
      raise ArgumentError, "Only Redis glob strings are supported: #{matcher.inspect}"
    end
    redis.with do |c|
      pattern = namespace_key(matcher, options)
      cursor = "0"
      # Fetch keys in batches using SCAN to avoid blocking the Redis server.
      nodes = c.respond_to?(:nodes) ? c.nodes : [c]

      nodes.each do |node|
        begin
          cursor, keys = node.scan(cursor, match: pattern, count: SCAN_BATCH_SIZE)
          node.del(*keys) unless keys.empty?
        end until cursor == "0"
      end
    end
  end
end

#increment(name, amount = 1, options = nil) ⇒ Object

Cache Store API implementation.

Increment a cached value. This method uses the Redis incr atomic operator and can only be used on values written with the :raw option. Calling it on a value not stored with :raw will initialize that value to zero.

Failsafe: Raises errors.


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 269

def increment(name, amount = 1, options = nil)
  instrument :increment, name, amount: amount do
    failsafe :increment do
      options = merged_options(options)
      key = normalize_key(name, options)

      redis.with do |c|
        c.incrby(key, amount).tap do
          write_key_expiry(c, key, options)
        end
      end
    end
  end
end

#inspect ⇒ Object 


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 204

def inspect
  instance = @redis || @redis_options
  "<##{self.class} options=#{options.inspect} redis=#{instance.inspect}>"
end

#mget_capable? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 

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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 329

def mget_capable? #:nodoc:
  set_redis_capabilities unless defined? @mget_capable
  @mget_capable
end

#mset_capable? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 

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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 334

def mset_capable? #:nodoc:
  set_redis_capabilities unless defined? @mset_capable
  @mset_capable
end

#read_multi(*names) ⇒ Object

Cache Store API implementation.

Read multiple values at once. Returns a hash of requested keys -> fetched values.


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 213

def read_multi(*names)
  if mget_capable?
    instrument(:read_multi, names, options) do |payload|
      read_multi_mget(*names).tap do |results|
        payload[:hits] = results.keys
      end
    end
  else
    super
  end
end

#redis ⇒ Object 


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# File 'activesupport/lib/active_support/cache/redis_cache_store.rb', line 191

def redis
  @redis ||= begin
    pool_options = self.class.send(:retrieve_pool_options, redis_options)

    if pool_options.any?
      self.class.send(:ensure_connection_pool_added!)
      ::ConnectionPool.new(pool_options) { self.class.build_redis(**redis_options) }
    else
      self.class.build_redis(**redis_options)
    end
  end
end