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
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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.
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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.
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Constants
DEFAULT_ERROR_HANDLER | = | -> (method:, returning:, exception:) do if logger logger.error { "RedisCacheStore: #{method} failed, returned #{returning.inspect}: #{exception.class}: #{exception.message}" } end ActiveSupport.error_reporter&.report( exception, severity: :warning, source: "redis_cache_store.active_support", ) end |
DEFAULT_REDIS_OPTIONS | = | { connect_timeout: 1, read_timeout: 1, write_timeout: 1, } |
MAX_KEY_BYTESIZE | = | 1024 |
Keys are truncated with the Active Support digest if they exceed 1kB |
Attributes
[R] | max_key_bytesize | |
[R] | redis |
Class Public methods
new(error_handler: DEFAULT_ERROR_HANDLER, **redis_options) Link
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
# File activesupport/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
supports_cache_versioning?() Link
Advertise cache versioning support.
Instance Public methods
cleanup(options = nil) Link
clear(options = nil) Link
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) Link
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.
# File activesupport/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) change_counter(key, -amount, options) end end end
delete_matched(matcher, options = nil) Link
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 198 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.then 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) Link
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.
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 236 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) change_counter(key, amount, options) end end end
inspect() Link
read_multi(*names) Link
Cache
Store
API implementation.
Read multiple values at once. Returns a hash of requested keys -> fetched values.
# File activesupport/lib/active_support/cache/redis_cache_store.rb, line 172 def read_multi(*names) return {} if names.empty? options = names.extract_options! instrument_multi(:read_multi, names, options) do |payload| read_multi_entries(names, **options).tap do |results| payload[:hits] = results.keys end end end