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# frozen_string_literal: true
# Add capabilities to increment a numeric model attribute efficiently by
# using Redis and flushing the increments asynchronously to the database
# after a period of time (10 minutes).
# When an attribute is incremented by a value, the increment is added
# to a Redis key. Then, FlushCounterIncrementsWorker will execute
# `flush_increments_to_database!` which removes increments from Redis for a
# given model attribute and updates the values in the database.
#
# @example:
#
# class ProjectStatistics
# include CounterAttribute
#
# counter_attribute :commit_count
# counter_attribute :storage_size
# end
#
# It's possible to define a conditional counter attribute. You need to pass a proc
# that must accept a single argument, the object instance on which this concern is
# included.
#
# @example:
#
# class ProjectStatistics
# include CounterAttribute
#
# counter_attribute :conditional_one, if: -> { |object| object.use_counter_attribute? }
# end
#
# To increment the counter we can use the method:
# increment_counter(:commit_count, 3)
#
# This method would determine whether it would increment the counter using Redis,
# or fallback to legacy increment on ActiveRecord counters.
#
# It is possible to register callbacks to be executed after increments have
# been flushed to the database. Callbacks are not executed if there are no increments
# to flush.
#
# counter_attribute_after_commit do |statistic|
# Namespaces::ScheduleAggregationWorker.perform_async(statistic.namespace_id)
# end
#
module CounterAttribute
extend ActiveSupport::Concern
extend AfterCommitQueue
include Gitlab::ExclusiveLeaseHelpers
include Gitlab::Utils::StrongMemoize
class_methods do
def counter_attribute(attribute, if: nil)
counter_attributes << {
attribute: attribute,
if_proc: binding.local_variable_get(:if) # can't read `if` directly
}
end
def counter_attributes
@counter_attributes ||= []
end
def after_commit_callbacks
@after_commit_callbacks ||= []
end
# perform registered callbacks after increments have been committed to the database
def counter_attribute_after_commit(&callback)
after_commit_callbacks << callback
end
end
def counter_attribute_enabled?(attribute)
counter_attribute = self.class.counter_attributes.find { |registered| registered[:attribute] == attribute }
return false unless counter_attribute
return true unless counter_attribute[:if_proc]
counter_attribute[:if_proc].call(self)
end
def counter(attribute)
strong_memoize_with(:counter, attribute) do
# This needs #to_sym because attribute could come from a Sidekiq param,
# which would be a string.
build_counter_for(attribute.to_sym)
end
end
def increment_counter(attribute, increment)
return if increment == 0
run_after_commit_or_now do
new_value = counter(attribute).increment(increment)
log_increment_counter(attribute, increment, new_value)
end
end
def update_counters_with_lease(increments)
detect_race_on_record(log_fields: { caller: __method__, attributes: increments.keys }) do
self.class.update_counters(id, increments)
end
end
def reset_counter!(attribute)
detect_race_on_record(log_fields: { caller: __method__, attributes: attribute }) do
counter(attribute).reset!
end
log_clear_counter(attribute)
end
def execute_after_commit_callbacks
self.class.after_commit_callbacks.each do |callback|
callback.call(self.reset)
end
end
private
def build_counter_for(attribute)
raise ArgumentError, %(attribute "#{attribute}" does not exist) unless has_attribute?(attribute)
if counter_attribute_enabled?(attribute)
Gitlab::Counters::BufferedCounter.new(self, attribute)
else
Gitlab::Counters::LegacyCounter.new(self, attribute)
end
end
def database_lock_key
"project:{#{project_id}}:#{self.class}:#{id}"
end
# detect_race_on_record uses a lease to monitor access
# to the project statistics row. This is needed to detect
# concurrent attempts to increment columns, which could result in a
# race condition.
#
# As the purpose is to detect and warn concurrent attempts,
# it falls back to direct update on the row if it fails to obtain the lease.
#
# It does not guarantee that there will not be any concurrent updates.
def detect_race_on_record(log_fields: {})
return yield unless Feature.enabled?(:counter_attribute_db_lease_for_update, project)
# Ensure attributes is always an array before we log
log_fields[:attributes] = Array(log_fields[:attributes])
Gitlab::AppLogger.info(
message: 'Acquiring lease for project statistics update',
project_statistics_id: id,
project_id: project.id,
**log_fields,
**Gitlab::ApplicationContext.current
)
in_lock(database_lock_key, retries: 0) do
yield
end
rescue Gitlab::ExclusiveLeaseHelpers::FailedToObtainLockError
Gitlab::AppLogger.warn(
message: 'Concurrent project statistics update detected',
project_statistics_id: id,
project_id: project.id,
**log_fields,
**Gitlab::ApplicationContext.current
)
yield
end
def log_increment_counter(attribute, increment, new_value)
payload = Gitlab::ApplicationContext.current.merge(
message: 'Increment counter attribute',
attribute: attribute,
project_id: project_id,
increment: increment,
new_counter_value: new_value,
current_db_value: read_attribute(attribute)
)
Gitlab::AppLogger.info(payload)
end
def log_clear_counter(attribute)
payload = Gitlab::ApplicationContext.current.merge(
message: 'Clear counter attribute',
attribute: attribute,
project_id: project_id
)
Gitlab::AppLogger.info(payload)
end
end
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