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February 13, 2022 08:50
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Override cache key and touch methods in active record when we cannot update the last modified / updated at column in database. We keep track of the changes in memcache.
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module CacheKeyMonkeyPatch | |
module ActiveRecord | |
module Integration | |
# Returns a cache key that can be used to identify this record. | |
# | |
# ==== Examples | |
# | |
# Product.new.cache_key # => "products/new" | |
# Product.find(5).cache_key # => "products/5" (updated_at / last_modified_time not available) | |
# Person.find(5).cache_key # => "people/5-20140227181414671756000" (updated_at / last_modified_time available) | |
def cache_key | |
last_update_timestamp = Rails.cache.read(object_key) | |
return "#{self.class.model_name.cache_key}/#{id}-#{last_update_timestamp}" if last_update_timestamp | |
case | |
when new_record? | |
cached_cache_key = "#{self.class.model_name.cache_key}/new" | |
when timestamp = (self[:updated_at] || self.respond_to?(:last_modified_time) && self.last_modified_time) | |
timestamp = timestamp.to_s(:nsec) | |
Rails.logger.info "\e[33m READ: #{object_key} from nil to #{timestamp}" | |
Rails.cache.write(object_key, timestamp) | |
cached_cache_key = "#{self.class.model_name.cache_key}/#{id}-#{timestamp}" | |
else | |
cached_cache_key = "#{self.class.model_name.cache_key}/#{id}" | |
end | |
cached_cache_key | |
end | |
end | |
end | |
end | |
ActiveRecord::Base.class_eval do | |
include CacheKeyMonkeyPatch::ActiveRecord::Integration | |
end | |
module ActiveRecord | |
class Base | |
def update_cache_key_for_associated_belongs_to_models(event) | |
belongs_to_associations_to_touch = self.class.reflect_on_all_associations(:belongs_to).select { |assoc| assoc.options[:touch] } | |
belongs_to_associations_to_touch.each do |belongs_to_assoc| | |
associated_object = self.send(belongs_to_assoc.name) | |
associated_object.touch("PROPAGATE from #{self.class.to_s}") if associated_object | |
end | |
end | |
def touch(event = nil) | |
event ||= 'CREATE' | |
cached_timestamp = Rails.cache.fetch(object_key) || 'nil' | |
new_timestamp = Time.zone.now.to_s(:nsec) | |
Rails.logger.info "\e[33m #{event} #{object_key} from #{cached_timestamp} to #{new_timestamp}" | |
Rails.cache.write(object_key, new_timestamp) | |
update_cache_key_for_associated_belongs_to_models(event) | |
end | |
def object_key | |
"cache_key_#{self.class.model_name.i18n_key}_#{self.id}" | |
end | |
end | |
end |
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