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Versions: 65
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Contents
# Used to perform locked, atomic writes to the data file.
module Scout
class DataFile
attr_accessor :path, :logger
attr_reader :data
def initialize(path,logger)
@path = path
@logger = logger
end
# atomic_write first writes to the tmp file.
def tmp_path
path+'.tmp'
end
# saves the data file by (1) locking the file at +path+ to ensure other processes
# don't overlap (2) using an atomic write to ensure other processes always read a complete file.
def save(content)
lock do
atomic_write(content)
end
end
private
def lock
File.open(path, File::RDWR | File::CREAT) do |f|
begin
f.flock(File::LOCK_EX)
yield
ensure
f.flock(File::LOCK_UN)
end
end
rescue Errno::ENOENT, Exception => e
logger.error("Unable to access data file [#{e.message}]")
end
# Uses an Atomic Write - first writes to a tmp file then replace the history file.
# Ensures reads on the history file don't see a partial write.
def atomic_write(content)
File.open(tmp_path, 'w+') do |f|
f.write(content)
end
FileUtils.mv(tmp_path, path)
end
end
end
Version data entries
65 entries across 65 versions & 1 rubygems