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.
Keys are truncated with the ActiveSupport
digest if they exceed 1kB
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 143 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
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.
ActiveSupport::Cache::Store::new
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 69 def self.supports_cache_versioning? true end
Advertise cache versioning support.
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 275 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.
ActiveSupport::Cache::Store#cleanup
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 283 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.
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 256 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
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.
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 204 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
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.
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 233 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
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.
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 168 def inspect instance = @redis || @redis_options "#<#{self.class} options=#{options.inspect} redis=#{instance.inspect}>" end
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 177 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.
ActiveSupport::Cache::Store#read_multi
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 155 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
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 294 def stats redis.with { |c| c.info } end
Get info from redis servers.
© 2004–2021 David Heinemeier Hansson
Licensed under the MIT License.