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Contents
# frozen_string_literal: true
module MalawiHivProgramReports
module Utils
module ConcurrencyUtils
LOCK_FILES_DIR_PATH = Rails.root.join('tmp', 'locks')
##
# Acquire a lock and run the given block of code.
#
# The locking mechanism uses files to allow for blocking across processes.
# This is useful for example in situations where you only want to run one
# instance of a report.
#
# Parameters:
# lock_file_path: A relative path to the lock file (allows for namespacing your locks, eg art_service/regimens.lock)
# blocking: If lock can not be acquired wait else throw an error (defaults to true)
#
# Raises:
# FailedToAcquireLock: When lock couldn't be acquired and blocking is set to false
#
# Usage:
# class Someclass
# include ModelUtils
#
# def do_something
# with_lock('mylockfile.lock') do
# # Run some task requiring exclusive access to some resource
# end
# end
# end
#
# SomeClass.new.do_something
def with_lock(lock_file_path, blocking: true)
path = LOCK_FILES_DIR_PATH.join(lock_file_path)
unless Dir.exist?(path.dirname)
Rails.logger.debug("Creating lock file directory: #{path.dirname}")
::FileUtils.mkdir_p(path.dirname)
end
File.open(path, 'w') do |lock_file|
Rails.logger.debug("Attempting to acquire lock: #{lock_file_path}")
locked = lock_file.flock(blocking ? File::LOCK_EX : File::LOCK_NB | File::LOCK_EX)
raise ::FailedToAcquireLock, "Lock #{lock_file_path} is locked by another process" if !locked && !blocking
lock_file.write("Locked by process ##{Process.pid} at #{Time.now}")
yield
end
end
end
end
end
Version data entries
44 entries across 44 versions & 1 rubygems