sr_watch crashes when encountering file it can't read

[EricFunk]

If a directory is being watched with sr_watch and someone goes in and attempts to create a new file with:

vi somefile

The presence of the unreadable swap file '.somefile.swp'. causes the observer to trigger a creation event, then when sr_post.py attempts to compute a checksum. The following line:

fp = open(path,'rb')

triggers an exception, but since it isn't handled the sr_watch process completely crashes. Here is the resulting error message:

2019-07-31 13:31:32,901 [DEBUG] trim_headers
2019-07-31 13:31:32,902 [DEBUG] sum set by compute_sumstr
2019-07-31 13:31:32,902 [DEBUG] sr_config set_sumalgo d
2019-07-31 13:31:32,976 [ERROR] Traceback (most recent call last):
2019-07-31 13:31:32,977 [ERROR]   File "/usr/bin/sr_watch", line 11, in <module>
2019-07-31 13:31:32,977 [ERROR] load_entry_point('metpx-sarracenia==2.19.4b2', 'console_scripts', 'sr_watch')()
2019-07-31 13:31:32,978 [ERROR]   File "/usr/lib/python3/dist-packages/sarra/sr_watch.py", line 65, in main
2019-07-31 13:31:32,978 [ERROR] watch.exec_action(action,old)
2019-07-31 13:31:32,978 [ERROR]   File "/usr/lib/python3/dist-packages/sarra/sr_instances.py", line 301, in exec_action
2019-07-31 13:31:32,978 [ERROR] elif action == 'start'      : self.start_parent()
2019-07-31 13:31:32,979 [ERROR]   File "/usr/lib/python3/dist-packages/sarra/sr_instances.py", line 785, in start_parent
2019-07-31 13:31:32,979 [ERROR] self.start()
2019-07-31 13:31:32,979 [ERROR]   File "/usr/lib/python3/dist-packages/sarra/sr_post.py", line 1480, in start
2019-07-31 13:31:32,980 [ERROR] self.run()
2019-07-31 13:31:32,980 [ERROR]   File "/usr/lib/python3/dist-packages/sarra/sr_post.py", line 1467, in run
2019-07-31 13:31:32,981 [ERROR] if self.sleep > 0: self.watch_loop()
2019-07-31 13:31:32,981 [ERROR]   File "/usr/lib/python3/dist-packages/sarra/sr_post.py", line 1285, in watch_loop
2019-07-31 13:31:32,981 [ERROR] self.wakeup()
2019-07-31 13:31:32,981 [ERROR]   File "/usr/lib/python3/dist-packages/sarra/sr_post.py", line 1161, in wakeup
2019-07-31 13:31:32,982 [ERROR] done = self.process_event( event, src, dst )
2019-07-31 13:31:32,982 [ERROR]   File "/usr/lib/python3/dist-packages/sarra/sr_post.py", line 1056, in process_event
2019-07-31 13:31:32,982 [ERROR] ok = self.post1file(src,lstat)
2019-07-31 13:31:32,982 [ERROR]   File "/usr/lib/python3/dist-packages/sarra/sr_post.py", line 981, in post1file
2019-07-31 13:31:32,983 [ERROR] ok = self.post_file(path,lstat)
2019-07-31 13:31:32,983 [ERROR]   File "/usr/lib/python3/dist-packages/sarra/sr_post.py", line 541, in post_file
2019-07-31 13:31:32,983 [ERROR] sumstr = self.compute_sumstr(path, fsiz)
2019-07-31 13:31:32,983 [ERROR]   File "/usr/lib/python3/dist-packages/sarra/sr_post.py", line 622, in compute_sumstr
2019-07-31 13:31:32,984 [ERROR] fp = open(path,'rb')
2019-07-31 13:31:32,984 [ERROR] PermissionError
2019-07-31 13:31:32,984 [ERROR] :
2019-07-31 13:31:32,984 [ERROR] [Errno 13] Permission denied: '/apps/bullprep/fcsts/transmit/uplink-transmit/.test10.swp'

I imagine a reject statement can be included to ignore these types of files, but I am guessing it should perhaps cause an error message and not cause it to crash.

[benlapETS]

• I agree with you this shouldnt crash. This is part of the bad coding practice that led the dev of sr_post that I am trying to fix for a while. But from my side, I added handling when file was not found but I guess I will have to expand the handling to OSError to be less specific as we learn how to handle each case properly.

• BTW, why would we need to watch hidden files/folder ? is there some cases that we want to watch them ? I guess it wouldnt be the rule but the exception...

[benlapETS]

I pushed the fix directly to master, give me some feedback if you see any problem.

[petersilva]

@EricFunk ... this fix should be available in daily builds that you can get from
the daily repo:

https://launchpad.net/~ssc-hpc-chp-spc/+archive/ubuntu/metpx-daily

if there is some place you want to test it.

[petersilva]

fix released in 2.19.09