Am 08.07.2012 13:29, schrieb Richard Baron Penman:
> My initial solution was a thread that writes status to a tmp file
> first and then renames:
>
> open(tmp_file, 'w').write(status)
> os.rename(tmp_file, status_file)
You algorithm may not write and flush all data to disk. You need to do
additional work. You must also store the tmpfile on the same partition
(better: same directory) as the status file
with open(tmp_file, "w") as f:
f.write(status)
# flush buffer and write data/metadata to disk
f.flush()
os.fsync(f.fileno())
# now rename the file
os.rename(tmp_file, status_file)
# finally flush metadata of directory to disk
dirfd = os.open(os.path.dirname(status_file), os.O_RDONLY)
try:
os.fsync(dirfd)
finally:
os.close(dirfd)
> This works well on Linux but Windows raises an error when status_file
> already exists.
> http://docs.python.org/library/os.html#os.rename
Windows doesn't suppport atomic renames if the right side exists. I
suggest that you implement two code paths:
if os.name == "posix":
rename = os.rename
else:
def rename(a, b):
try:
os.rename(a, b)
except OSError, e:
if e.errno != 183:
raise
os.unlink(b)
os.rename(a, b)
Christian
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