hometown/app/controllers/concerns/cache_concern.rb

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# frozen_string_literal: true
module CacheConcern
extend ActiveSupport::Concern
module ActiveRecordCoder
EMPTY_HASH = {}.freeze
class << self
def dump(record)
instances = InstanceTracker.new
serialized_associations = serialize_associations(record, instances)
serialized_records = instances.map { |r| serialize_record(r) }
[serialized_associations, *serialized_records]
end
def load(payload)
instances = InstanceTracker.new
serialized_associations, *serialized_records = payload
serialized_records.each { |attrs| instances.push(deserialize_record(*attrs)) }
deserialize_associations(serialized_associations, instances)
end
private
# Records without associations, or which have already been visited before,
# are serialized by their id alone.
#
# Records with associations are serialized as a two-element array including
# their id and the record's association cache.
#
def serialize_associations(record, instances)
return unless record
if (id = instances.lookup(record))
payload = id
else
payload = instances.push(record)
cached_associations = record.class.reflect_on_all_associations.select do |reflection|
record.association_cached?(reflection.name)
end
unless cached_associations.empty?
serialized_associations = cached_associations.map do |reflection|
association = record.association(reflection.name)
serialized_target = if reflection.collection?
association.target.map { |target_record| serialize_associations(target_record, instances) }
else
serialize_associations(association.target, instances)
end
[reflection.name, serialized_target]
end
payload = [payload, serialized_associations]
end
end
payload
end
def deserialize_associations(payload, instances)
return unless payload
id, associations = payload
record = instances.fetch(id)
associations&.each do |name, serialized_target|
begin
association = record.association(name)
rescue ActiveRecord::AssociationNotFoundError
raise AssociationMissingError, "undefined association: #{name}"
end
target = if association.reflection.collection?
serialized_target.map! { |serialized_record| deserialize_associations(serialized_record, instances) }
else
deserialize_associations(serialized_target, instances)
end
association.target = target
end
record
end
def serialize_record(record)
arguments = [record.class.name, attributes_for_database(record)]
arguments << true if record.new_record?
arguments
end
if Rails.gem_version >= Gem::Version.new('7.0')
def attributes_for_database(record)
attributes = record.attributes_for_database
attributes.transform_values! { |attr| attr.is_a?(::ActiveModel::Type::Binary::Data) ? attr.to_s : attr }
attributes
end
else
def attributes_for_database(record)
attributes = record.instance_variable_get(:@attributes).send(:attributes).transform_values(&:value_for_database)
attributes.transform_values! { |attr| attr.is_a?(::ActiveModel::Type::Binary::Data) ? attr.to_s : attr }
attributes
end
end
def deserialize_record(class_name, attributes_from_database, new_record = false) # rubocop:disable Style/OptionalBooleanParameter
begin
klass = Object.const_get(class_name)
rescue NameError
raise ClassMissingError, "undefined class: #{class_name}"
end
# Ideally we'd like to call `klass.instantiate`, however it doesn't allow to pass
# wether the record was persisted or not.
attributes = klass.attributes_builder.build_from_database(attributes_from_database, EMPTY_HASH)
klass.allocate.init_with_attributes(attributes, new_record)
end
end
class Error < StandardError
end
class ClassMissingError < Error
end
class AssociationMissingError < Error
end
class InstanceTracker
def initialize
@instances = []
@ids = {}.compare_by_identity
end
def map(&block)
@instances.map(&block)
end
def fetch(...)
@instances.fetch(...)
end
def push(instance)
id = @ids[instance] = @instances.size
@instances << instance
id
end
def lookup(instance)
@ids[instance]
end
end
end
class_methods do
def vary_by(value)
before_action do |controller|
response.headers['Vary'] = value.respond_to?(:call) ? controller.instance_exec(&value) : value
end
end
end
included do
after_action :enforce_cache_control!
end
# Prevents high-entropy headers such as `Cookie`, `Signature` or `Authorization`
# from being used as cache keys, while allowing to `Vary` on them (to not serve
# anonymous cached data to authenticated requests when authentication matters)
def enforce_cache_control!
vary = response.headers['Vary']&.split&.map { |x| x.strip.downcase }
return unless vary.present? && %w(cookie authorization signature).any? { |header| vary.include?(header) && request.headers[header].present? }
response.cache_control.replace(private: true, no_store: true)
end
def render_with_cache(**options)
raise ArgumentError, 'Only JSON render calls are supported' unless options.key?(:json) || block_given?
key = options.delete(:key) || [[params[:controller], params[:action]].join('/'), options[:json].respond_to?(:cache_key) ? options[:json].cache_key : nil, options[:fields].nil? ? nil : options[:fields].join(',')].compact.join(':')
expires_in = options.delete(:expires_in) || 3.minutes
body = Rails.cache.read(key, raw: true)
if body
render(options.except(:json, :serializer, :each_serializer, :adapter, :fields).merge(json: body))
else
if block_given?
options[:json] = yield
elsif options[:json].is_a?(Symbol)
options[:json] = send(options[:json])
end
render(options)
Rails.cache.write(key, response.body, expires_in: expires_in, raw: true)
end
end
def cache_collection(raw, klass)
return raw unless klass.respond_to?(:with_includes)
raw = raw.cache_ids.to_a if raw.is_a?(ActiveRecord::Relation)
return [] if raw.empty?
cached_keys_with_value = begin
Rails.cache.read_multi(*raw).transform_keys(&:id).transform_values { |r| ActiveRecordCoder.load(r) }
rescue ActiveRecordCoder::Error
{} # The serialization format may have changed, let's pretend it's a cache miss.
end
uncached_ids = raw.map(&:id) - cached_keys_with_value.keys
klass.reload_stale_associations!(cached_keys_with_value.values) if klass.respond_to?(:reload_stale_associations!)
unless uncached_ids.empty?
uncached = klass.where(id: uncached_ids).with_includes.index_by(&:id)
uncached.each_value do |item|
Rails.cache.write(item, ActiveRecordCoder.dump(item))
end
end
raw.filter_map { |item| cached_keys_with_value[item.id] || uncached[item.id] }
end
def cache_collection_paginated_by_id(raw, klass, limit, options)
cache_collection raw.cache_ids.to_a_paginated_by_id(limit, options), klass
end
end