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class ActiveSupport::Cache::RedisCacheStore

Parent:
ActiveSupport::Cache::Store

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.

Constants

DEFAULT_ERROR_HANDLER
DEFAULT_REDIS_OPTIONS
MAX_KEY_BYTESIZE

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

Attributes

max_key_bytesize[R]
redis_options[R]

Public Class Methods

new(namespace: nil, compress: true, compress_threshold: 1.kilobyte, expires_in: nil, race_condition_ttl: nil, error_handler: DEFAULT_ERROR_HANDLER, **redis_options) Show source
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 174
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

Creates a new Redis cache store.

Handles three options: block provided to instantiate, single URL provided, and multiple URLs provided.

: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: <tt>namespace: 'myapp-cache'<tt>.

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.

Calls superclass method ActiveSupport::Cache::Store.new

Public Instance Methods

cleanup(options = nil) Show source
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 287
def cleanup(options = nil)
  super
end

Cache Store API implementation.

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

Calls superclass method ActiveSupport::Cache::Store#cleanup
clear(options = nil) Show source
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 295
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

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

Failsafe: Raises errors.

decrement(name, amount = 1, options = nil) Show source
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 275
def decrement(name, amount = 1, options = nil)
  instrument :decrement, name, amount: amount do
    failsafe :decrement do
      redis.with { |c| c.decrby normalize_key(name, options), amount }
    end
  end
end

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.

delete_matched(matcher, options = nil) Show source
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 234
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.
      begin
        cursor, keys = c.scan(cursor, match: pattern, count: SCAN_BATCH_SIZE)
        c.del(*keys) unless keys.empty?
      end until cursor == "0"
    end
  end
end

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.

increment(name, amount = 1, options = nil) Show source
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 259
def increment(name, amount = 1, options = nil)
  instrument :increment, name, amount: amount do
    failsafe :increment do
      redis.with { |c| c.incrby normalize_key(name, options), amount }
    end
  end
end

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.

inspect() Show source
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 198
def inspect
  instance = @redis || @redis_options
  "<##{self.class} options=#{options.inspect} redis=#{instance.inspect}>"
end
read_multi(*names) Show source
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 207
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

Cache Store API implementation.

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

Calls superclass method ActiveSupport::Cache::Store#read_multi
redis() Show source
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 185
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

© 2004–2018 David Heinemeier Hansson
Licensed under the MIT License.