diff options
Diffstat (limited to 'activesupport/lib/active_support/cache/redis_cache_store.rb')
| -rw-r--r-- | activesupport/lib/active_support/cache/redis_cache_store.rb | 485 |
1 files changed, 485 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/cache/redis_cache_store.rb b/activesupport/lib/active_support/cache/redis_cache_store.rb new file mode 100644 index 0000000000..9a55e49e27 --- /dev/null +++ b/activesupport/lib/active_support/cache/redis_cache_store.rb @@ -0,0 +1,485 @@ +# frozen_string_literal: true + +begin + gem "redis", ">= 4.0.1" + require "redis" + require "redis/distributed" +rescue LoadError + warn "The Redis cache store requires the redis gem, version 4.0.1 or later. Please add it to your Gemfile: `gem \"redis\", \"~> 4.0\"`" + raise +end + +# Prefer the hiredis driver but don't require it. +begin + require "redis/connection/hiredis" +rescue LoadError +end + +require "digest/sha2" +require "active_support/core_ext/marshal" + +module ActiveSupport + module Cache + module ConnectionPoolLike + def with + yield self + end + end + + ::Redis.include(ConnectionPoolLike) + ::Redis::Distributed.include(ConnectionPoolLike) + + # 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: https://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. + class RedisCacheStore < Store + # Keys are truncated with their own SHA2 digest if they exceed 1kB + MAX_KEY_BYTESIZE = 1024 + + DEFAULT_REDIS_OPTIONS = { + connect_timeout: 20, + read_timeout: 1, + write_timeout: 1, + reconnect_attempts: 0, + } + + DEFAULT_ERROR_HANDLER = -> (method:, returning:, exception:) do + if logger + logger.error { "RedisCacheStore: #{method} failed, returned #{returning.inspect}: #{exception.class}: #{exception.message}" } + end + end + + # The maximum number of entries to receive per SCAN call. + SCAN_BATCH_SIZE = 1000 + private_constant :SCAN_BATCH_SIZE + + # Advertise cache versioning support. + def self.supports_cache_versioning? + true + end + + # Support raw values in the local cache strategy. + module LocalCacheWithRaw # :nodoc: + private + def read_entry(key, options) + entry = super + if options[:raw] && local_cache && entry + entry = deserialize_entry(entry.value) + end + entry + end + + def write_entry(key, entry, options) + if options[:raw] && local_cache + raw_entry = Entry.new(serialize_entry(entry, raw: true)) + raw_entry.expires_at = entry.expires_at + super(key, raw_entry, options) + else + super + end + end + + def write_multi_entries(entries, options) + if options[:raw] && local_cache + raw_entries = entries.map do |key, entry| + raw_entry = Entry.new(serialize_entry(entry, raw: true)) + raw_entry.expires_at = entry.expires_at + end.to_h + + super(raw_entries, options) + else + super + end + end + end + + prepend Strategy::LocalCache + prepend LocalCacheWithRaw + + class << self + # Factory method to create a new Redis instance. + # + # 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: … }, …]) + # + def build_redis(redis: nil, url: nil, **redis_options) #:nodoc: + urls = Array(url) + + if redis.is_a?(Proc) + redis.call + elsif redis + redis + elsif urls.size > 1 + build_redis_distributed_client urls: urls, **redis_options + else + build_redis_client url: urls.first, **redis_options + end + end + + private + 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 + + def build_redis_client(url:, **redis_options) + ::Redis.new DEFAULT_REDIS_OPTIONS.merge(redis_options.merge(url: url)) + end + end + + attr_reader :redis_options + attr_reader :max_key_bytesize + + # 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 <tt>compress: false</tt> or change the threshold by passing + # <tt>compress_threshold: 4.kilobytes</tt>. + # + # 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 https://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 <tt>ActiveSupport::Cache::Store#fetch</tt> for more. + 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 + + 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 + + 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. + 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 + + # 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 https://redis.io/commands/KEYS for more. + # + # Failsafe: Raises errors. + 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 + + # 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. + 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 + + # 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. + 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. + # + # Removes expired entries. Handled natively by Redis least-recently-/ + # least-frequently-used expiry, so manual cleanup is not supported. + 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. + 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 + + def mget_capable? #:nodoc: + set_redis_capabilities unless defined? @mget_capable + @mget_capable + end + + def mset_capable? #:nodoc: + set_redis_capabilities unless defined? @mset_capable + @mset_capable + end + + private + def set_redis_capabilities + case redis + when Redis::Distributed + @mget_capable = true + @mset_capable = false + else + @mget_capable = true + @mset_capable = true + end + end + + # Store provider interface: + # Read an entry from the cache. + def read_entry(key, options = nil) + failsafe :read_entry do + deserialize_entry redis.with { |c| c.get(key) } + end + end + + def read_multi_entries(names, _options) + if mget_capable? + read_multi_mget(*names) + else + super + end + end + + 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 + + # Write an entry to the cache. + # + # Requires Redis 2.6.12+ for extended SET options. + 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 + + 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 + + # Delete an entry from the cache. + def delete_entry(key, options) + failsafe :delete_entry, returning: false do + redis.with { |c| c.del key } + end + end + + # Nonstandard store provider API to write multiple values at once. + 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 + + # Truncate keys that exceed 1kB. + def normalize_key(key, options) + truncate_key super.b + end + + 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 + + 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 + + def serialize_entry(entry, raw: false) + if raw + entry.value.to_s + else + Marshal.dump(entry) + end + end + + def serialize_entries(entries, raw: false) + entries.transform_values do |entry| + serialize_entry entry, raw: raw + end + end + + def failsafe(method, returning: nil) + yield + rescue ::Redis::BaseConnectionError => e + handle_exception exception: e, method: method, returning: returning + returning + end + + 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 + end + end +end |