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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

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

1024

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 a few ways to provide the Redis client used by the cache:

  1. The :redis param can be:

    • A Redis instance.

    • A ConnectionPool instance wrapping a Redis instance.

    • A block that returns a Redis instance.

  2. The :url param can be:

    • A string used to create a Redis instance.

    • An array of strings used to create a Redis::Distributed instance.

If the final Redis instance is not already a ConnectionPool, it will be wrapped in one using ActiveSupport::Cache::Store::DEFAULT_POOL_OPTIONS. These options can be overridden with the :pool param, or the pool can be disabled with +:pool: false+.

Option  Class       Result
:redis  Object  ->  options[:redis]
:redis  Proc    ->  options[:redis].call
: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 159
def initialize(error_handler: DEFAULT_ERROR_HANDLER, **redis_options)
  universal_options = redis_options.extract!(*UNIVERSAL_OPTIONS)
  redis = redis_options[:redis]

  already_pool = redis.instance_of?(::ConnectionPool) ||
                 (redis.respond_to?(:wrapped_pool) && redis.wrapped_pool.instance_of?(::ConnectionPool))

  if !already_pool && 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 296
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 304
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 281
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 215
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 254
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 178
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 186
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 315
def stats
  redis.then { |c| c.info }
end

Definition files