[Bug 1020048] Re: after certain time printing to cups stops working

[Ryan Tandy]

> I've uploaded it with a slightly modified version number for
processing by the ubuntu-sru team.

haha, I called it -ubuntu9 this time around because of bdmurray's
comment (#50) :)

all good, thanks for uploading Marc!

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https://bugs.launchpad.net/bugs/1020048

Title:
  after certain time printing to cups stops working

Status in LibreOffice Productivity Suite:
  Invalid
Status in “cups” package in Ubuntu:
  Fix Released
Status in “libreoffice” package in Ubuntu:
  Invalid
Status in “cups” source package in Precise:
  In Progress
Status in “libreoffice” source package in Precise:
  Invalid

Bug description:
  SRU justification:

  [Impact]

  * When the CUPS client connects to a remote cupsd over TCP, the server 
    closes an idle connection after 5 minutes and the client does not reconnect.

  * LibreOffice is affected because it keeps a CUPS connection open. The 
    effect is that printing to a remote cupsd is no longer possible after 
    LibreOffice has been open for 5 minutes.

  [Test Case]

  * This can be reproduced on a desktop system. You don't need a separate 
    CUPS server.

  * You need at least one print queue in CUPS. If you don't have a 
    printer, install "cups-pdf".

  * Optional, configure CUPS with a shorter timeout for testing:

    sudo cupsctl Timeout=30 # seconds
    sudo restart cups

  * Configure the CUPS client to use a TCP socket:

    mkdir ~/.cups
    echo ServerName 127.0.0.1 > ~/.cups/client.conf

  * Open LibreOffice. Press Ctrl-P to open the Print dialog. Press Esc to 
    dismiss the dialog. Wait long enough for the timout to elapse (5 
    minutes by default, or as per the Timeout setting).

  * Try to print. With cups in precise, the job simply vanishes and is 
    never seen by the server. With the proposed patch, printing works 
    normally.

  [Regression Potential]

  * The patch changes a library linked by many programs. An incorrect 
    change might result in those programs misbehaving or crashing.

  * The patch is minimal, only adding a branch to handle a case that was 
    previously not handled. The behaviour in other cases should be 
    unchanged.

  [Other Info]

  * A workaround is to set the cupsd Timeout to a high value such as 8 
    hours. This works on a server with few users, but on a busy server 
    more and more connections are opened and eventually cupsd isn't able 
    to accept new clients.

  Original description:

  == Problem ==
  In our institution we are running only printers through a cups server. while freshly opened document prints well, after some time (few minutes) clicking "print file directly" and menu item "print" do not work any more. after close and open again, thing prints correctly. i have checked what exactly is going on in such cases and logs on the cups server don't show any submissions and/or errors so that the thing is obviously stopped at the level of libreoffice.

  == Analysis ==
  LibreOffice loses it's TCP connection to CUPS after exactly 5 minutes of inactivity and does not manage to reconnect. To reproduce: print something (to a real printer or cups-pdf), wait 6 minutes not printing anything, and print again. Then, nothing is printed. You can watch the TCP connection using
  netstat -tpn | grep soffice
  While it's working, it looks like this:
  tcp        0      0 127.0.0.1:48810         127.0.0.1:631           ESTABLISHED 13976/soffice.bin
  After 5 minutes, that connection is gone permanently.

  WORKAROUND: To set the timeout to 24 hours add this line to the top of /etc/cups/cupsd.conf :
  Timeout 62400

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