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Fixed inotify race conditions and fd leak in scripts

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Since we were only registering our inotify reader after the previous
operation completed, it was easy to miss modifications that happened
faster than our scripts. Since our scripts are in Python, this happened
quite often and made it hard to trust the current state of scripts
with --keep-open, sort of defeating the purpose of --keep-open...

I think previously this race condition wasn't avoided because of the
potential to loop indefinitely if --keep-open referenced a file that the
script itself modified, but it's up to the user to avoid this if it is
an issue.

---

Also while fixing this, I noticed our use of the inotify_simple library
was leaking file descriptors everywhere! I just wasn't closing any
inotify objects at all. A bit concerning since scripts with --keep-open
can be quite long lived...
This commit is contained in:
Christopher Haster
2023-11-29 13:14:05 -06:00
parent a9772d785a
commit b8d3a5ef46
2 changed files with 85 additions and 65 deletions
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60
scripts/plot.py
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@@ -140,30 +140,32 @@ def openio(path, mode='r', buffering=-1):
else:
return open(path, mode, buffering)
def inotifywait(paths):
# wait for interesting events
inotify = inotify_simple.INotify()
flags = (inotify_simple.flags.ATTRIB
| inotify_simple.flags.CREATE
| inotify_simple.flags.DELETE
| inotify_simple.flags.DELETE_SELF
| inotify_simple.flags.MODIFY
| inotify_simple.flags.MOVED_FROM
| inotify_simple.flags.MOVED_TO
| inotify_simple.flags.MOVE_SELF)
if inotify_simple is None:
Inotify = None
else:
class Inotify(inotify_simple.INotify):
def __init__(self, paths):
super().__init__()
# recurse into directories
for path in paths:
if os.path.isdir(path):
for dir, _, files in os.walk(path):
inotify.add_watch(dir, flags)
for f in files:
inotify.add_watch(os.path.join(dir, f), flags)
else:
inotify.add_watch(path, flags)
# wait for interesting events
flags = (inotify_simple.flags.ATTRIB
| inotify_simple.flags.CREATE
| inotify_simple.flags.DELETE
| inotify_simple.flags.DELETE_SELF
| inotify_simple.flags.MODIFY
| inotify_simple.flags.MOVED_FROM
| inotify_simple.flags.MOVED_TO
| inotify_simple.flags.MOVE_SELF)
# wait for event
inotify.read()
# recurse into directories
for path in paths:
if os.path.isdir(path):
for dir, _, files in os.walk(path):
self.add_watch(dir, flags)
for f in files:
self.add_watch(os.path.join(dir, f), flags)
else:
self.add_watch(path, flags)
class LinesIO:
def __init__(self, maxlen=None):
@@ -1392,6 +1394,11 @@ def main(csv_paths, *,
if keep_open:
try:
while True:
# register inotify before running the command, this avoids
# modification race conditions
if keep_open and Inotify:
inotify = Inotify(csv_paths)
if cat:
draw(sys.stdout)
else:
@@ -1400,11 +1407,12 @@ def main(csv_paths, *,
ring.draw()
# try to inotifywait
if inotify_simple is not None:
if keep_open and Inotify:
ptime = time.time()
inotifywait(csv_paths)
# sleep for a minimum amount of time, this helps issues
# around rapidly updating files
inotify.read()
inotify.close()
# sleep for a minimum amount of time, this helps reduce
# flicker issues
time.sleep(max(0, (sleep or 0.01) - (time.time()-ptime)))
else:
time.sleep(sleep or 0.1)