class ActiveSupport::Cache::RedisCacheStore
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
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Supports vanilla Redis, hiredis, and Redis::Distributed.
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Supports Memcached-like sharding across Redises with Redis::Distributed.
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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.
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read_multi
andwrite_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 the
ActiveSupport
digest if they exceed 1kB- SCAN_BATCH_SIZE
The maximum number of entries to receive per SCAN call.
Attributes
Public Class Methods
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 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
Advertise cache versioning support.
# File lib/active_support/cache/redis_cache_store.rb, line 73 def self.supports_cache_versioning? true end
Private Class Methods
# File lib/active_support/cache/redis_cache_store.rb, line 114 def build_redis_client(**redis_options) ::Redis.new(DEFAULT_REDIS_OPTIONS.merge(redis_options)) end
# File lib/active_support/cache/redis_cache_store.rb, line 108 def build_redis_distributed_client(urls:, **redis_options) ::Redis::Distributed.new([], DEFAULT_REDIS_OPTIONS.merge(redis_options)).tap do |dist| urls.each { |u| dist.add_node url: u } end end
Public Instance Methods
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 lib/active_support/cache/redis_cache_store.rb, line 281 def cleanup(options = nil) super end
Clear the entire cache on all Redis servers. Safe to use on shared servers if the cache is namespaced.
Failsafe: Raises errors.
# 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
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 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
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 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
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 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
# 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
Cache
Store
API implementation.
Read multiple values at once. Returns a hash of requested keys -> fetched values.
ActiveSupport::Cache::Store#read_multi
# 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
# 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
Get info from redis servers.
# File lib/active_support/cache/redis_cache_store.rb, line 300 def stats redis.with { |c| c.info } end
Private Instance Methods
Delete an entry from the cache.
# File lib/active_support/cache/redis_cache_store.rb, line 403 def delete_entry(key, options) failsafe :delete_entry, returning: false do redis.with { |c| c.del key } end end
Deletes multiple entries in the cache. Returns the number of entries deleted.
# File lib/active_support/cache/redis_cache_store.rb, line 410 def delete_multi_entries(entries, **_options) redis.with { |c| c.del(entries) } end
ActiveSupport::Cache::Store#deserialize_entry
# File lib/active_support/cache/redis_cache_store.rb, line 445 def deserialize_entry(payload, raw: false, **) if raw && !payload.nil? Entry.new(payload) else super(payload) end end
# File lib/active_support/cache/redis_cache_store.rb, line 467 def failsafe(method, returning: nil) yield rescue ::Redis::BaseError => error ActiveSupport.error_reporter&.report(error, handled: true, severity: :warning) @error_handler&.call(method: method, exception: error, returning: returning) returning end
Truncate keys that exceed 1kB.
ActiveSupport::Cache::Store#normalize_key
# File lib/active_support/cache/redis_cache_store.rb, line 431 def normalize_key(key, options) truncate_key super&.b end
Store
provider interface: Read an entry from the cache.
# File lib/active_support/cache/redis_cache_store.rb, line 330 def read_entry(key, **options) deserialize_entry(read_serialized_entry(key, **options), **options) end
ActiveSupport::Cache::Store#read_multi_entries
# File lib/active_support/cache/redis_cache_store.rb, line 340 def read_multi_entries(names, **options) if mget_capable? read_multi_mget(*names, **options) else super end end
# File lib/active_support/cache/redis_cache_store.rb, line 348 def read_multi_mget(*names) options = names.extract_options! options = merged_options(options) return {} if names == [] raw = options&.fetch(:raw, false) keys = names.map { |name| normalize_key(name, options) } values = failsafe(:read_multi_mget, returning: {}) do redis.with { |c| c.mget(*keys) } end names.zip(values).each_with_object({}) do |(name, value), results| if value entry = deserialize_entry(value, raw: raw) unless entry.nil? || entry.expired? || entry.mismatched?(normalize_version(name, options)) results[name] = entry.value end end end end
# File lib/active_support/cache/redis_cache_store.rb, line 334 def read_serialized_entry(key, raw: false, **options) failsafe :read_entry do redis.with { |c| c.get(key) } end end
# File lib/active_support/cache/redis_cache_store.rb, line 461 def serialize_entries(entries, **options) entries.transform_values do |entry| serialize_entry(entry, **options) end end
ActiveSupport::Cache::Store#serialize_entry
# File lib/active_support/cache/redis_cache_store.rb, line 453 def serialize_entry(entry, raw: false, **options) if raw entry.value.to_s else super(entry, raw: raw, **options) end end
# File lib/active_support/cache/redis_cache_store.rb, line 315 def set_redis_capabilities redis.with do |c| case c when Redis::Distributed @mget_capable = true @mset_capable = false else @mget_capable = true @mset_capable = true end end end
# File lib/active_support/cache/redis_cache_store.rb, line 435 def truncate_key(key) if key && key.bytesize > max_key_bytesize suffix = ":hash:#{ActiveSupport::Digest.hexdigest(key)}" truncate_at = max_key_bytesize - suffix.bytesize "#{key.byteslice(0, truncate_at)}#{suffix}" else key end end
Write an entry to the cache.
Requires Redis 2.6.12+ for extended SET options.
# File lib/active_support/cache/redis_cache_store.rb, line 373 def write_entry(key, entry, raw: false, **options) write_serialized_entry(key, serialize_entry(entry, raw: raw, **options), raw: raw, **options) end
# File lib/active_support/cache/redis_cache_store.rb, line 396 def write_key_expiry(client, key, options) if options[:expires_in] && client.ttl(key).negative? client.expire key, options[:expires_in].to_i end end
Nonstandard store provider API to write multiple values at once.
ActiveSupport::Cache::Store#write_multi_entries
# File lib/active_support/cache/redis_cache_store.rb, line 415 def write_multi_entries(entries, expires_in: nil, **options) if entries.any? if mset_capable? && expires_in.nil? failsafe :write_multi_entries do payload = serialize_entries(entries, **options) redis.with do |c| c.mapped_mset(payload) end end else super end end end
# File lib/active_support/cache/redis_cache_store.rb, line 377 def write_serialized_entry(key, payload, raw: false, unless_exist: false, expires_in: nil, race_condition_ttl: nil, **options) # If race condition TTL is in use, ensure that cache entries # stick around a bit longer after they would have expired # so we can purposefully serve stale entries. if race_condition_ttl && expires_in && expires_in > 0 && !raw expires_in += 5.minutes end modifiers = {} if unless_exist || expires_in modifiers[:nx] = unless_exist modifiers[:px] = (1000 * expires_in.to_f).ceil if expires_in end failsafe :write_entry, returning: false do redis.with { |c| c.set key, payload, **modifiers } end end