Path: csiph.com!usenet.pasdenom.info!news.redatomik.org!newsfeed.xs4all.nl!newsfeed4a.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Date: Tue, 31 Mar 2015 16:50:12 +0200
From: Ervin =?utf-8?Q?Heged=C3=BCs?= <airween@gmail.com>
To: python-list@python.org
Subject: Lockfile hanling
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
User-Agent: Mutt/1.5.21 (2010-09-15)
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.374.1427813384.10327.python-list@python.org>
Lines: 45
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:88385

Hello,

there is an app, written in Python, which stores few bytes of
datas in a single file. The application uses threads. Every
thread can modify the file, but only one at a time. I'm using a
lock file to prevent the multiple access.

Here is the lock method:

  while True:
      try:
          fl = os.open(self.lockfile, os.O_CREAT | os.O_EXCL | os.O_RDWR)
      except OSError, e:
          if e.errno != errno.EEXIST:
              raise
          time.sleep(0.2)
          continue
      except:
          syslog.syslog(syslog.LOG_DEBUG, "Sync error: " + str(sys.exc_info()[1]))
      else:
          break

This works as well for me - about 3-4 weeks. After some weeks, I
got this error:

OSError: [Errno 24] Too many open files: '/var/spool/myapp/queue.lock'


Today the app had been restarted, about 3-4 hours ago. Now I see
under the proc/PID/fd:

lrwx------ 1 root     root     64 márc 31 16.45 5 -> /var/spool/myapp/queue.lock (deleted)

there are about 50 deleted FD's. After few weeks the process
reaches the number if max fd's.

How can I prevent or avoid this issue? What's the correct way to
handle the lockfile in Python?


Thanks,


Ervin