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
andwrite_multi
support for Redis mget/mset. UseRedis::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 Active Support digest if they exceed 1kB
- SCAN_BATCH_SIZE
-
The maximum number of entries to receive per SCAN call.
Attributes
Public Class Methods
Source
# File lib/active_support/cache/redis_cache_store.rb, line 149 def initialize(error_handler: DEFAULT_ERROR_HANDLER, **redis_options) universal_options = redis_options.extract!(*UNIVERSAL_OPTIONS) if 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
Creates a new Redis cache store.
There are four ways to provide the Redis client used by the cache: the :redis
param can be a Redis instance or a block that returns a Redis instance, or the :url
param can be a string or an array of strings which will be used to create a Redis instance or a Redis::Distributed
instance.
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.
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
ActiveSupport::Cache::Store::new
Source
# File lib/active_support/cache/redis_cache_store.rb, line 63 def self.supports_cache_versioning? true end
Advertise cache versioning support.
Private Class Methods
Source
# File lib/active_support/cache/redis_cache_store.rb, line 104 def build_redis_client(**redis_options) ::Redis.new(DEFAULT_REDIS_OPTIONS.merge(redis_options)) end
Source
# File lib/active_support/cache/redis_cache_store.rb, line 98 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
Source
# File lib/active_support/cache/redis_cache_store.rb, line 282 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
Source
# File lib/active_support/cache/redis_cache_store.rb, line 290 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
Clear the entire cache on all Redis servers. Safe to use on shared servers if the cache is namespaced.
Failsafe: Raises errors.
Source
# File lib/active_support/cache/redis_cache_store.rb, line 267 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
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
# File lib/active_support/cache/redis_cache_store.rb, line 201 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
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
# File lib/active_support/cache/redis_cache_store.rb, line 240 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
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
# File lib/active_support/cache/redis_cache_store.rb, line 164 def inspect "#<#{self.class} options=#{options.inspect} redis=#{redis.inspect}>" end
Source
# File lib/active_support/cache/redis_cache_store.rb, line 172 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
Cache
Store
API implementation.
Read multiple values at once. Returns a hash of requested keys -> fetched values.
Source
# File lib/active_support/cache/redis_cache_store.rb, line 301 def stats redis.then { |c| c.info } end
Get info from redis servers.
Private Instance Methods
Source
# File lib/active_support/cache/redis_cache_store.rb, line 450 def change_counter(key, amount, options) redis.then do |c| c = c.node_for(key) if c.is_a?(Redis::Distributed) expires_in = options[:expires_in] if expires_in if supports_expire_nx? count, _ = c.pipelined do |pipeline| pipeline.incrby(key, amount) pipeline.call(:expire, key, expires_in.to_i, "NX") end else count, ttl = c.pipelined do |pipeline| pipeline.incrby(key, amount) pipeline.ttl(key) end c.expire(key, expires_in.to_i) if ttl < 0 end else count = c.incrby(key, amount) end count end end
Source
# File lib/active_support/cache/redis_cache_store.rb, line 385 def delete_entry(key, **options) failsafe :delete_entry, returning: false do redis.then { |c| c.del(key) == 1 } end end
Delete an entry from the cache.
Source
# File lib/active_support/cache/redis_cache_store.rb, line 392 def delete_multi_entries(entries, **_options) failsafe :delete_multi_entries, returning: 0 do redis.then { |c| c.del(entries) } end end
Deletes multiple entries in the cache. Returns the number of entries deleted.
Source
# File lib/active_support/cache/redis_cache_store.rb, line 428 def deserialize_entry(payload, raw: false, **) if raw && !payload.nil? Entry.new(payload) else super(payload) end end
ActiveSupport::Cache::Store#deserialize_entry
Source
# File lib/active_support/cache/redis_cache_store.rb, line 484 def failsafe(method, returning: nil) yield rescue ::Redis::BaseError => error @error_handler&.call(method: method, exception: error, returning: returning) returning end
Source
# File lib/active_support/cache/redis_cache_store.rb, line 414 def normalize_key(key, options) truncate_key super&.b end
Truncate keys that exceed 1kB.
ActiveSupport::Cache::Store#normalize_key
Source
# File lib/active_support/cache/redis_cache_store.rb, line 306 def pipeline_entries(entries, &block) redis.then { |c| if c.is_a?(Redis::Distributed) entries.group_by { |k, _v| c.node_for(k) }.each do |node, sub_entries| node.pipelined { |pipe| yield(pipe, sub_entries) } end else c.pipelined { |pipe| yield(pipe, entries) } end } end
Source
# File lib/active_support/cache/redis_cache_store.rb, line 320 def read_entry(key, **options) deserialize_entry(read_serialized_entry(key, **options), **options) end
Store
provider interface: Read an entry from the cache.
Source
# File lib/active_support/cache/redis_cache_store.rb, line 330 def read_multi_entries(names, **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_entries, returning: {}) do redis.then { |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)) begin results[name] = entry.value rescue DeserializationError end end end end end
Source
# File lib/active_support/cache/redis_cache_store.rb, line 324 def read_serialized_entry(key, raw: false, **options) failsafe :read_entry do redis.then { |c| c.get(key) } end end
Source
# File lib/active_support/cache/redis_cache_store.rb, line 444 def serialize_entries(entries, **options) entries.transform_values do |entry| serialize_entry(entry, **options) end end
Source
# File lib/active_support/cache/redis_cache_store.rb, line 436 def serialize_entry(entry, raw: false, **options) if raw entry.value.to_s else super(entry, raw: raw, **options) end end
ActiveSupport::Cache::Store#serialize_entry
Source
# File lib/active_support/cache/redis_cache_store.rb, line 477 def supports_expire_nx? return @supports_expire_nx if defined?(@supports_expire_nx) redis_versions = redis.then { |c| Array.wrap(c.info("server")).pluck("redis_version") } @supports_expire_nx = redis_versions.all? { |v| Gem::Version.new(v) >= Gem::Version.new("7.0.0") } end
Source
# File lib/active_support/cache/redis_cache_store.rb, line 418 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
Source
# File lib/active_support/cache/redis_cache_store.rb, line 357 def write_entry(key, entry, raw: false, **options) write_serialized_entry(key, serialize_entry(entry, raw: raw, **options), raw: raw, **options) end
Write an entry to the cache.
Requires Redis 2.6.12+ for extended SET options.
Source
# File lib/active_support/cache/redis_cache_store.rb, line 399 def write_multi_entries(entries, **options) return if entries.empty? failsafe :write_multi_entries do pipeline_entries(entries) do |pipeline, sharded_entries| options = options.dup options[:pipeline] = pipeline sharded_entries.each do |key, entry| write_entry key, entry, **options end end end end
Nonstandard store provider API to write multiple values at once.
Source
# File lib/active_support/cache/redis_cache_store.rb, line 361 def write_serialized_entry(key, payload, raw: false, unless_exist: false, expires_in: nil, race_condition_ttl: nil, pipeline: 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 if pipeline pipeline.set(key, payload, **modifiers) else failsafe :write_entry, returning: nil do redis.then { |c| !!c.set(key, payload, **modifiers) } end end end