Class: ActiveSupport::Cache::RedisCacheStore

Inherits:
Store show all
Includes:
Strategy::LocalCache
Defined in:
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.

Constant Summary collapse

MAX_KEY_BYTESIZE =

Keys are truncated with the ActiveSupport 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 included from Strategy::LocalCache

#middleware, #with_local_cache

Methods inherited from Store

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

Constructor Details

#initialize(namespace: nil, compress: true, compress_threshold: 1.kilobyte, coder: default_coder, 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.



149
150
151
152
153
154
155
156
157
158
159
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 149

def initialize(namespace: nil, compress: true, compress_threshold: 1.kilobyte, coder: default_coder, 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,
    coder: coder
end

Instance Attribute Details

#max_key_bytesize ⇒ Object (readonly)

Returns the value of attribute max_key_bytesize.



120
121
122
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 120

def max_key_bytesize
  @max_key_bytesize
end

#redis_options ⇒ Object (readonly)

Returns the value of attribute redis_options.



119
120
121
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 119

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: … }, …])



91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 91

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)
  elsif urls.empty?
    build_redis_client(**redis_options)
  else
    build_redis_client(url: urls.first, **redis_options)
  end
end

.supports_cache_versioning? ⇒ Boolean

Advertise cache versioning support.

Returns:

  • (Boolean) 


73
74
75
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 73

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.



281
282
283
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 281

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.



289
290
291
292
293
294
295
296
297
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 289

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.



262
263
264
265
266
267
268
269
270
271
272
273
274
275
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 262

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.



210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 210

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.



239
240
241
242
243
244
245
246
247
248
249
250
251
252
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 239

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 



174
175
176
177
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 174

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

#mget_capable? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


304
305
306
307
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 304

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

#mset_capable? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


309
310
311
312
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 309

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.



183
184
185
186
187
188
189
190
191
192
193
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 183

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 



161
162
163
164
165
166
167
168
169
170
171
172
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 161

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

#stats ⇒ Object

Get info from redis servers.



300
301
302
 
# File 'lib/active_support/cache/redis_cache_store.rb', line 300

def stats
  redis.with { |c| c.info }
end