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

Constants

DEFAULT_ERROR_HANDLER
DEFAULT_REDIS_OPTIONS
MAX_KEY_BYTESIZE

Keys are truncated with their own SHA2 digest if they exceed 1kB

SCAN_BATCH_SIZE

The maximum number of entries to receive per SCAN call.

Attributes

max_key_bytesize[R]
redis_options[R]

Public Class Methods

new(namespace: nil, compress: true, compress_threshold: 1.kilobyte, expires_in: nil, race_condition_ttl: nil, error_handler: DEFAULT_ERROR_HANDLER, **redis_options) click to toggle source

Creates a new Redis cache store.

Handles three options: block provided to instantiate, single URL provided, and multiple URLs provided.

:redis Proc   -> options[:redis].call
: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: <tt>namespace: 'myapp-cache'<tt>.

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.

Calls superclass method ActiveSupport::Cache::Store.new
# File lib/active_support/cache/redis_cache_store.rb, line 174
def initialize(namespace: nil, compress: true, compress_threshold: 1.kilobyte, 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
end

Private Class Methods

build_redis_client(url:, **redis_options) click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 141
def build_redis_client(url:, **redis_options)
  ::Redis.new DEFAULT_REDIS_OPTIONS.merge(redis_options.merge(url: url))
end
build_redis_distributed_client(urls:, **redis_options) click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 135
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) click to toggle source

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
# File lib/active_support/cache/redis_cache_store.rb, line 287
def cleanup(options = nil)
  super
end
clear(options = nil) click to toggle source

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 295
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
decrement(name, amount = 1, options = nil) click to toggle source

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 275
def decrement(name, amount = 1, options = nil)
  instrument :decrement, name, amount: amount do
    failsafe :decrement do
      redis.with { |c| c.decrby normalize_key(name, options), amount }
    end
  end
end
delete_matched(matcher, options = nil) click to toggle source

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 234
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.
      begin
        cursor, keys = c.scan(cursor, match: pattern, count: SCAN_BATCH_SIZE)
        c.del(*keys) unless keys.empty?
      end until cursor == "0"
    end
  end
end
increment(name, amount = 1, options = nil) click to toggle source

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 259
def increment(name, amount = 1, options = nil)
  instrument :increment, name, amount: amount do
    failsafe :increment do
      redis.with { |c| c.incrby normalize_key(name, options), amount }
    end
  end
end
inspect() click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 198
def inspect
  instance = @redis || @redis_options
  "<##{self.class} options=#{options.inspect} redis=#{instance.inspect}>"
end
read_multi(*names) click to toggle source

Cache Store API implementation.

Read multiple values at once. Returns a hash of requested keys -> fetched values.

Calls superclass method ActiveSupport::Cache::Store#read_multi
# File lib/active_support/cache/redis_cache_store.rb, line 207
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
redis() click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 185
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

Private Instance Methods

delete_entry(key, options) click to toggle source

Delete an entry from the cache.

# File lib/active_support/cache/redis_cache_store.rb, line 390
def delete_entry(key, options)
  failsafe :delete_entry, returning: false do
    redis.with { |c| c.del key }
  end
end
deserialize_entry(serialized_entry) click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 424
def deserialize_entry(serialized_entry)
  if serialized_entry
    entry = Marshal.load(serialized_entry) rescue serialized_entry
    entry.is_a?(Entry) ? entry : Entry.new(entry)
  end
end
failsafe(method, returning: nil) { || ... } click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 445
def failsafe(method, returning: nil)
  yield
rescue ::Redis::BaseConnectionError => e
  handle_exception exception: e, method: method, returning: returning
  returning
end
handle_exception(exception:, method:, returning:) click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 452
def handle_exception(exception:, method:, returning:)
  if @error_handler
    @error_handler.(method: method, exception: exception, returning: returning)
  end
rescue => failsafe
  warn "RedisCacheStore ignored exception in handle_exception: #{failsafe.class}: #{failsafe.message}\n  #{failsafe.backtrace.join("\n  ")}"
end
normalize_key(key, options) click to toggle source

Truncate keys that exceed 1kB.

# File lib/active_support/cache/redis_cache_store.rb, line 410
def normalize_key(key, options)
  truncate_key super.b
end
read_entry(key, options = nil) click to toggle source

Store provider interface: Read an entry from the cache.

# File lib/active_support/cache/redis_cache_store.rb, line 329
def read_entry(key, options = nil)
  failsafe :read_entry do
    deserialize_entry redis.with { |c| c.get(key) }
  end
end
read_multi_entries(names, _options) click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 335
def read_multi_entries(names, _options)
  if mget_capable?
    read_multi_mget(*names)
  else
    super
  end
end
read_multi_mget(*names) click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 343
def read_multi_mget(*names)
  options = names.extract_options!
  options = merged_options(options)

  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)
      unless entry.nil? || entry.expired? || entry.mismatched?(normalize_version(name, options))
        results[name] = entry.value
      end
    end
  end
end
serialize_entries(entries, raw: false) click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 439
def serialize_entries(entries, raw: false)
  entries.transform_values do |entry|
    serialize_entry entry, raw: raw
  end
end
serialize_entry(entry, raw: false) click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 431
def serialize_entry(entry, raw: false)
  if raw
    entry.value.to_s
  else
    Marshal.dump(entry)
  end
end
set_redis_capabilities() click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 316
def set_redis_capabilities
  case redis
  when Redis::Distributed
    @mget_capable = true
    @mset_capable = false
  else
    @mget_capable = true
    @mset_capable = true
  end
end
truncate_key(key) click to toggle source
# File lib/active_support/cache/redis_cache_store.rb, line 414
def truncate_key(key)
  if key.bytesize > max_key_bytesize
    suffix = ":sha2:#{::Digest::SHA2.hexdigest(key)}"
    truncate_at = max_key_bytesize - suffix.bytesize
    "#{key.byteslice(0, truncate_at)}#{suffix}"
  else
    key
  end
end
write_entry(key, entry, unless_exist: false, raw: false, expires_in: nil, race_condition_ttl: nil, **options) click to toggle source

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 366
def write_entry(key, entry, unless_exist: false, raw: false, expires_in: nil, race_condition_ttl: nil, **options)
  serialized_entry = serialize_entry(entry, raw: raw)

  # 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

  failsafe :write_entry, returning: false do
    if unless_exist || expires_in
      modifiers = {}
      modifiers[:nx] = unless_exist
      modifiers[:px] = (1000 * expires_in.to_f).ceil if expires_in

      redis.with { |c| c.set key, serialized_entry, modifiers }
    else
      redis.with { |c| c.set key, serialized_entry }
    end
  end
end
write_multi_entries(entries, expires_in: nil, **options) click to toggle source

Nonstandard store provider API to write multiple values at once.

# File lib/active_support/cache/redis_cache_store.rb, line 397
def write_multi_entries(entries, expires_in: nil, **options)
  if entries.any?
    if mset_capable? && expires_in.nil?
      failsafe :write_multi_entries do
        redis.with { |c| c.mapped_mset(serialize_entries(entries, raw: options[:raw])) }
      end
    else
      super
    end
  end
end