Pattern: Use of non-atomic file operation
Issue: -
Checks for non-atomic file operation. And then replace it with a nearly equivalent and atomic method.
These can cause problems that are difficult to reproduce, especially in cases of frequent file operations in parallel, such as test runs with parallel_rspec.
For examples: creating a directory if there is none, has the following problems
An exception occurs when the directory didn’t exist at the time of exist?, but someone else created it before mkdir was executed.
Subsequent processes are executed without the directory that should be there when the directory existed at the time of exist?, but someone else deleted it shortly afterwards.
# bad
unless FileTest.exist?(path)
FileUtils.makedirs(path)
end
if FileTest.exist?(path)
FileUtils.remove(path)
end
# good
FileUtils.mkdir_p(path)
FileUtils.rm_rf(path)