I guess we could, though I have rarely seen programs do this. They
usually just to the std* descriptors.
---------------------------------------------------------------------------
Menno Smits wrote:
>
> The following bug has been logged online:
>
> Bug reference: 1958
> Logged by: Menno Smits
> Email address: menno@netboxblue.com
> PostgreSQL version: 8.0.3
> Operating system: Linux (Fedora Core 3)
> Description: Postmaster doesn't close open file handles on startup
> Details:
>
> The postmaster process doesn't close open file handles/sockets when it
> daemonises. This means it inherits all open file handles that the parent
> process had. This can lead to strange side effects because postgres will
> hold sockets and files that it really shouldn't.
>
> The following short Python script demonstrates the problem. It starts
> listening on TCP port 4444 and then restarts postgresql. Run with "python
> <script>.py".
>
> Postgresql should be running before the script is run.
> -----------------------------------------------------
> import os
> import socket
>
> # Start listening on TCP port 444
> s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
> s.bind(('127.0.0.1', 4444))
> s.listen(5)
>
> # Restart postgres
> os.system('/etc/init.d/postgresql restart')
>
> s.close()
> -----------------------------------------------------
>
> After the script is run use the following command to see what sockets
> postmaster has:
> netstat -tnlp | grep postmaster
>
> The output will be something like:
> tcp 0 0 127.0.0.1:5432 0.0.0.0:* LISTEN
> 5813/postmaster
> tcp 0 0 127.0.0.1:4444 0.0.0.0:* LISTEN
> 5813/postmaster
>
> Port 5432 makes sense but clearly it shouldn't be listening on 4444.
>
> Rerunning the python script will fail because postmaster still has the
> socket open:
> ------------------------------------------------------
> Traceback (most recent call last):
> File "postgres-bug.py", line 6, in ?
> s.bind(('127.0.0.1', 4444))
> File "<string>", line 1, in bind
> socket.error: (98, 'Address already in use')
> ------------------------------------------------------
>
> It is considered good UNIX programming practise to close open file handles
> when daemonising. See
> http://www.enderunix.org/docs/eng/daemon.php
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
> choose an index scan if your joining column's datatypes do not
> match
>
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
