class `ActiveSupport::Cache::RedisCacheStore`

Redis Cache Store

Deployment note: Take care to use a dedicated Redis cache rather than pointing this at a persistent Redis server (for example, one used as an Active Job queue). Redis 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.

Inherits From

class ActiveSupport::Cache::Store

Constants

`DEFAULT_ERROR_HANDLER`

-> (method:, returning:, exception:) do
if logger
logger.error { "RedisCacheStore: #{method} failed, returned #{returning.inspect}: #{exception.class}: #{exception.message}" }
end
ActiveSupport.error_reporter&.report(
exception,
severity: :warning,
source: "redis_cache_store.active_support",
)
end

`DEFAULT_REDIS_OPTIONS`

{
connect_timeout:    1,
read_timeout:       1,
write_timeout:      1,
}

`MAX_KEY_BYTESIZE`

Keys are truncated with the Active Support digest if they exceed 1kB

Attributes

[R]	`max_key_bytesize`
[R]	`redis`

Public class methods

`new(error_handler: DEFAULT_ERROR_HANDLER, **redis_options)`

Creates a new Redis cache store.

There are four ways to provide the Redis client used by the cache: the :redis param can be a Redis instance or a block that returns a Redis instance, or the :url param can be a string or an array of strings which will be used to create a Redis instance or a Redis::Distributed instance.

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.

Setting skip_nil: true will not cache nil results:

cache.fetch('foo') { nil }
cache.fetch('bar', skip_nil: true) { nil }
cache.exist?('foo') # => true
cache.exist?('bar') # => false

Source code GitHub

# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 149
def initialize(error_handler: DEFAULT_ERROR_HANDLER, **redis_options)
  universal_options = redis_options.extract!(*UNIVERSAL_OPTIONS)

  if pool_options = self.class.send(:retrieve_pool_options, redis_options)
    @redis = ::ConnectionPool.new(pool_options) { self.class.build_redis(**redis_options) }
  else
    @redis = self.class.build_redis(**redis_options)
  end

  @max_key_bytesize = MAX_KEY_BYTESIZE
  @error_handler = error_handler

  super(universal_options)
end

`supports_cache_versioning?()`

Advertise cache versioning support.

Source code GitHub

# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 63
def self.supports_cache_versioning?
  true
end

Public instance methods

`cleanup(options = nil)`

Cache Store API implementation.

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

Source code GitHub

# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 282
def cleanup(options = nil)
  super
end

`clear(options = nil)`

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

Failsafe: Raises errors.

Source code GitHub

# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 290
def clear(options = nil)
  failsafe :clear do
    if namespace = merged_options(options)[:namespace]
      delete_matched "*", namespace: namespace
    else
      redis.then { |c| c.flushdb }
    end
  end
end

`decrement(name, amount = 1, options = nil)`

Decrement a cached integer value using the Redis decrby atomic operator. Returns the updated value.

If the key is unset or has expired, it will be set to -amount:

cache.decrement("foo") # => -1

To set a specific value, call write passing raw: true:

cache.write("baz", 5, raw: true)
cache.decrement("baz") # => 4

Decrementing a non-numeric value, or a value written without raw: true, will fail and return nil.

Failsafe: Raises errors.

Source code GitHub

# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 267
def decrement(name, amount = 1, options = nil)
  options = merged_options(options)
  key = normalize_key(name, options)

  instrument :decrement, key, amount: amount do
    failsafe :decrement do
      change_counter(key, -amount, options)
    end
  end
end

`delete_matched(matcher, options = nil)`

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.

Source code GitHub

# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 201
def delete_matched(matcher, options = nil)
  unless String === matcher
    raise ArgumentError, "Only Redis glob strings are supported: #{matcher.inspect}"
  end
  pattern = namespace_key(matcher, options)

  instrument :delete_matched, pattern do
    redis.then do |c|
      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)`

Increment a cached integer value using the Redis incrby atomic operator. Returns the updated value.

If the key is unset or has expired, it will be set to amount:

cache.increment("foo") # => 1
cache.increment("bar", 100) # => 100

To set a specific value, call write passing raw: true:

cache.write("baz", 5, raw: true)
cache.increment("baz") # => 6

Incrementing a non-numeric value, or a value written without raw: true, will fail and return nil.

Failsafe: Raises errors.

Source code GitHub

# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 240
def increment(name, amount = 1, options = nil)
  options = merged_options(options)
  key = normalize_key(name, options)

  instrument :increment, key, amount: amount do
    failsafe :increment do
      change_counter(key, amount, options)
    end
  end
end

`inspect()`

Source code GitHub

# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 164
def inspect
  "#<#{self.class} options=#{options.inspect} redis=#{redis.inspect}>"
end

`read_multi(*names)`

Cache Store API implementation.

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

Source code GitHub

# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 172
def read_multi(*names)
  return {} if names.empty?

  options = names.extract_options!
  options = merged_options(options)
  keys    = names.map { |name| normalize_key(name, options) }

  instrument_multi(:read_multi, keys, options) do |payload|
    read_multi_entries(names, **options).tap do |results|
      payload[:hits] = results.keys.map { |name| normalize_key(name, options) }
    end
  end
end

`stats()`

Get info from redis servers.

Source code GitHub

# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 301
def stats
  redis.then { |c| c.info }
end

Definition files

activesupport/lib/active_support/cache/redis_cache_store.rb

class ActiveSupport::Cache::RedisCacheStore

Inherits From

Constants

DEFAULT_ERROR_HANDLER

DEFAULT_REDIS_OPTIONS

MAX_KEY_BYTESIZE

Attributes

Public class methods

new(error_handler: DEFAULT_ERROR_HANDLER, **redis_options)

supports_cache_versioning?()

Public instance methods

cleanup(options = nil)

clear(options = nil)

decrement(name, amount = 1, options = nil)

delete_matched(matcher, options = nil)

increment(name, amount = 1, options = nil)

inspect()

read_multi(*names)

stats()

Definition files

class `ActiveSupport::Cache::RedisCacheStore`

`DEFAULT_ERROR_HANDLER`

`DEFAULT_REDIS_OPTIONS`

`MAX_KEY_BYTESIZE`

`new(error_handler: DEFAULT_ERROR_HANDLER, **redis_options)`

`supports_cache_versioning?()`

`cleanup(options = nil)`

`clear(options = nil)`

`decrement(name, amount = 1, options = nil)`

`delete_matched(matcher, options = nil)`

`increment(name, amount = 1, options = nil)`

`inspect()`

`read_multi(*names)`

`stats()`