KeyError in __handle_inotify_event about pyinotify HOT 9 CLOSED

I'll have to take a look a it later today. This is a dictionary of all
current watches (using the "wd" a descriptor returned by the kernel for
each). It looks like the watch is being cleaned-up due to some other event.

On Sat, Jun 13, 2015 at 5:25 AM, backbord [email protected] wrote:

Hi, I've recently started to use your nice little project in version 0.2.3
(I used pyinotify before).
However, I stumbled across the following error and hope that you can help
me.

Traceback (most recent call last):
File "test.py", line 88, in
sys.exit(main())
File "test.py", line 82, in main
handle_events(path)
File "test.py", line 49, in handle_events
for event in notifier.event_gen():
File "/foo/bar/lib/python2.7/site-packages/inotify/adapters.py", line 193, in event_gen
for event in self.__i.event_gen():
File "/foo/bar/lib/python2.7/site-packages/inotify/adapters.py", line 148, in event_gen
in self.__handle_inotify_event(fd, event_type):
File "/foo/bar/lib/python2.7/site-packages/inotify/adapters.py", line 134, in __handle_inotify_event
path = self.__watches_r[header.wd]
KeyError: 226

The number varies. I've seen all from 9 to 10 and from 220 to 229.
Have you seen this error before and can advice?

The function handle_events(path) is intended to announce all files under
a path whenever they are closed after writing. It is defined as follows.

def handle_events(path):

# we intend to react on files being closed after writing and directories being created
mask = inotify.constants.IN_CLOSE_WRITE | inotify.constants.IN_CREATE

# block_duration_s is the pause [s] between calls to the kernel
# cycle: (poll for events, yield events sequentially, yield None, sleep for block_duration_s, loop)
notifier = inotify.adapters.InotifyTree(path=path, mask=mask, block_duration_s=1)

for event in notifier.event_gen():
    if event is None:
        continue

    (header, _type_names, watch_path, filename) = event

    # InotifyTree gives IN_ISDIR, IN_CREATE, IN_DELETE regardless of the actual mask for technical reasons
    # we ignore everything not in our mask
    if not header.mask & mask:
        continue

    # a file has been closed after writing. something to announce.
    if header.mask & inotify.constants.IN_CLOSE_WRITE:
        fpath = os.path.join(watch_path, filename)
        announce_file(fpath)

    # inotify adds a watch for the newly created path automatically (and removes it if the path is deleted)
    # but there might already be some files in the folder before the watch is active. let's make sure to announce them
    if header.mask & inotify.constants.IN_CREATE & inotify.constants.IN_ISDIR:
        announce_all(watch_path)

Best regards,
Tim

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#1.

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At closer inspection, the error pops up regularly after my cleanup process removed old files and empty subdirectories from the watched directory $HOME/mirror.

find $HOME/mirror -mmin +2880 -type f -exec rm -f {} \;
find $HOME/mirror -depth -type d -empty -exec rmdir {} \;

Could it be the case that the IN_DELETE events for files and directories which inotify creates are out of order (or read out of order by PyInotify) so that the watch for a subdir is removed (with del self.__watches_r[wd] in line 71 of adapters.py) before the IN_DELETE for a file in that subdir is processed?

Please let me know if I can help to find the cause. :-)

from pyinotify.

Hm, the watched $HOME/mirror gives PyInotify some trouble and as event_gen() is a generator, I'm having trouble handling exceptions from the outside.

From the traceback in my first post and the following one, I identified two places where removed watches appear to cause problems.

Traceback (most recent call last):
  File \"test.py\", line 88, in <module>
    sys.exit(main())
  File \"test.py\", line 82, in main
    handle_events(path)
  File \"test.py\", line 49, in handle_events
    for event in notifier.event_gen():
  File \"/foo/bar/lib/python2.7/site-packages/inotify/adapters.py\", line 215, in event_gen
    self.__i.remove_watch(full_path, superficial=True)
  File \"/foo/bar/lib/python2.7/site-packages/inotify/adapters.py\", line 68, in remove_watch
    wd = self.__watches[path]
KeyError: 'some/deleted/directory'

I'll let my program run with this patch to PyInotify and will get back to you if I see anything interesting.

--- inotify/adapters.py
+++ inotify/adapters.py
@@ -65,7 +65,9 @@
         our tracking since inotify already cleans-up the watch.
         """

-        wd = self.__watches[path]
+        wd = self.__watches.get(path)
+        if wd is None:
+            return

         del self.__watches[path]
         del self.__watches_r[wd]
@@ -131,7 +133,9 @@

             self.__buffer = self.__buffer[event_length:]

-            path = self.__watches_r[header.wd]
+            path = self.__watches_r.get(header.wd)
+            if path is None:
+                break
             yield (header, type_names, path, filename)

             buffer_length = len(self.__buffer)

Again, thanks for putting together such a nice straightforward code!

Best regards,
Tim

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Hmm. I prefer very strict code. However, as you mentioned before, things
might be coming in out-of-order (child events being received after the
child subdirectory was already removed).
On Jun 16, 2015 3:13 AM, "backbord" [email protected] wrote:

Hm, the watched $HOME/mirror gives PyInotify some trouble and as
event_gen() is a generator, I'm having trouble handling exceptions from
the outside.

From the traceback in my first post and the following one, I identified
two places where removed watches appear to cause problems.

Traceback (most recent call last):
File "test.py", line 88, in
sys.exit(main())
File "test.py", line 82, in main
handle_events(path)
File "test.py", line 49, in handle_events
for event in notifier.event_gen():
File "/foo/bar/lib/python2.7/site-packages/inotify/adapters.py", line 215, in event_gen
self.__i.remove_watch(full_path, superficial=True)
File "/foo/bar/lib/python2.7/site-packages/inotify/adapters.py", line 68, in remove_watch
wd = self.__watches[path]
KeyError: 'some/deleted/directory'

I'll let my program run with this patch to PyInotify and will get back to
you if I see anything interesting.

--- inotify/adapters.py+++ inotify/adapters.py@@ -65,7 +65,9 @@
our tracking since inotify already cleans-up the watch.
"""

•    wd = self.__watches[path]+        wd = self.__watches.get(path)+        if wd is None:+            return
  
   del self.__watches[path]
   del self.__watches_r[wd]@@ -131,7 +133,9 @@
  
       self.__buffer = self.__buffer[event_length:]
  

•        path = self.__watches_r[header.wd]+            path = self.__watches_r.get(header.wd)+            if path is None:+                break
       yield (header, type_names, path, filename)
  
       buffer_length = len(self.__buffer)
  

Again, thanks for putting together such a nice straightforward code!

Best regards,
Tim

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#1 (comment).

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Hi Dustin,
I can neither catch nor work around an exception thrown from the generator. (See for example http://stackoverflow.com/a/11366139/3985756)
However, I agree, that strict code is the way to go -- do you have an idea on how to cope with events being handled out-of-order?
My python is a bit too limited to come up with a straight-up answer. :-)

Best regards,
Tim

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I think your way is already the best way for IDs that aren't going to be
reappearing.

Dustin
On Jun 16, 2015 3:59 AM, "backbord" [email protected] wrote:

Hi Dustin,
I can neither catch nor work around an exception thrown from the
generator. (See for example http://stackoverflow.com/a/11366139/3985756)
However, I agree, that strict code is the way to go -- do you have an idea
on how to cope with events being handled out-of-order?
My python is a bit too limited to come up with a straight-up answer. :-)

Best regards,
Tim

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#1 (comment).

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If this seems to work, please submit a PR.

Dustin

On Tue, Jun 16, 2015 at 4:06 AM, Dustin Oprea [email protected]
wrote:

I think your way is already the best way for IDs that aren't going to be
reappearing.

Dustin
On Jun 16, 2015 3:59 AM, "backbord" [email protected] wrote:

Hi Dustin,
I can neither catch nor work around an exception thrown from the
generator. (See for example http://stackoverflow.com/a/11366139/3985756)
However, I agree, that strict code is the way to go -- do you have an
idea on how to cope with events being handled out-of-order?
My python is a bit too limited to come up with a straight-up answer. :-)

Best regards,
Tim

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#1 (comment).

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Ok, my first pull request ever. Hope it's to your liking. :-)

Thanks and regards,
Tim

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I've performed a release of 0.2.4. This includes the fix.

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