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 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.

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

max_key_bytesize [R]

redis [R]

Public Class Methods

new (error_handler: DEFAULT_ERROR_HANDLER, **redis_options)

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

Calls superclass method ActiveSupport::Cache::Store::new

supports_cache_versioning? ()

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

build_redis_client (**redis_options)

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

build_redis_distributed_client (urls:, **redis_options)

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

cleanup (options = nil)

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.

Calls superclass method ActiveSupport::Cache::Store#cleanup

clear (options = nil)

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.

decrement (name, amount = 1, options = nil)

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.

delete_matched (matcher, options = nil)

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.

increment (name, amount = 1, options = nil)

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.

inspect ()

Source

# File lib/active_support/cache/redis_cache_store.rb, line 164
def inspect
  "#<#{self.class} options=#{options.inspect} redis=#{redis.inspect}>"
end

read_multi (*names)

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.

stats ()

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

change_counter (key, amount, options)

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

delete_entry (key, **options)

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.

delete_multi_entries (entries, **_options)

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.

deserialize_entry (payload, raw: false, **)

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

Calls superclass method ActiveSupport::Cache::Store#deserialize_entry

failsafe (method, returning: nil) { || ... }

Source

# File lib/active_support/cache/redis_cache_store.rb, line 484
def failsafe(method, returning: nil)
  yield
rescue ::Redis::BaseError, ConnectionPool::Error, ConnectionPool::TimeoutError => error
  @error_handler&.call(method: method, exception: error, returning: returning)
  returning
end

normalize_key (key, options)

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.

Calls superclass method ActiveSupport::Cache::Store#normalize_key

pipeline_entries (entries) { |pipe, sub_entries| ... }

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

read_entry (key, **options)

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.

read_multi_entries (names, **options)

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

read_serialized_entry (key, raw: false, **options)

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

serialize_entries (entries, **options)

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

serialize_entry (entry, raw: false, **options)

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

Calls superclass method ActiveSupport::Cache::Store#serialize_entry

supports_expire_nx? ()

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

truncate_key (key)

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

write_entry (key, entry, raw: false, **options)

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.

write_multi_entries (entries, **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.

write_serialized_entry (key, payload, raw: false, unless_exist: false, expires_in: nil, race_condition_ttl: nil, pipeline: nil, **options)

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