cURL caching prevents landscape-broker from working

[Sidnei da Silva]

Apparently cURL might be caching failures to resolve DNS for way too long. When looking at my broker logs, I saw the following message repeated many many times:

2010-02-16 09:39:51,198 ERROR [Dummy-1 ] Error contacting the server at https://staging.landscape.canonical.com/message-system.
Traceback (most recent call last):
  File "/usr/lib/python2.6/dist-packages/landscape/broker/transport.py", line 63, in exchange
    curly, data = self._curl(spayload, computer_id, message_api)
  File "/usr/lib/python2.6/dist-packages/landscape/broker/transport.py", line 41, in _curl
    headers=headers, cainfo=self._pubkey, curl=curl))
  File "/usr/lib/python2.6/dist-packages/landscape/lib/fetch.py", line 91, in fetch
    raise PyCurlError(e.args[0], e.args[1])
PyCurlError: Error 6: Couldn't resolve host 'staging.landscape.canonical.com'

It's unclear if that's actually related to DNS caching, but it's the best guess so far.

The message below explains the different options for DNS caching, straight from the author:

  http://curl.haxx.se/mail/lib-2002-01/0076.html

[Kevin McDermott (bigkevmcd)]

http://curl.haxx.se/mail/lib-2002-01/0076.html

    curl_easy_setopt(handle, CURLOPT_DNS_CACHE_TIMEOUT, 15);

    With two special cases, 0 and -1... O will completely disable dns
    caching and -1 will make it so that the DNS cache *never* expires.

[Andreas Hasenack (ahasenack)]

Confirmed code in staging packages. Also induced DNS errors with iptables, and both positive and negative DNS results were not cached, i.e., the client transitioned between both states quickly.

[Martin Pitt (pitti)]

Accepted landscape-client into karmic-proposed, the package will build now and be available in a few hours. Please test and give feedback here. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you in advance!

[Martin Pitt (pitti)]

Accepted landscape-client into jaunty-proposed, the package will build now and be available in a few hours. Please test and give feedback here. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you in advance!

[Launchpad Janitor (janitor)]

This bug was fixed in the package landscape-client - 1.5.0.1-0ubuntu0.9.04.0

---------------
landscape-client (1.5.0.1-0ubuntu0.9.04.0) jaunty-proposed; urgency=low

  * New upstream version
    - Fix smart-update failing its very first run (LP: #562496)
    - Depend on pythonX.Y-dbus and pythonX.Y-pycurl (LP: #563063)
    - Make only one request at a time to retrieve EC2 instances (LP: #567515)

  * New upstream version (LP: #557244)
    - Fix package-changer running before smart-update has completed (LP: #542215)
    - Report the version of Eucalyptus used to generate topology data (LP: #554007)
    - Enable the Eucalyptus plugin by default, if supported (LP: #546531)
    - Use a whitelist of allowed filesystem types to instead of a blacklist (LP: #351927)
    - Report the update-manager logs to the server (LP: #503384)
    - Turn off Curl's DNS caching for requests. (LP: #522668)
 -- Free Ekanayaka <email address hidden> Wed, 21 Apr 2010 12:31:28 +0200

[Launchpad Janitor (janitor)]

This bug was fixed in the package landscape-client - 1.5.0.1-0ubuntu0.9.10.0

---------------
landscape-client (1.5.0.1-0ubuntu0.9.10.0) karmic-proposed; urgency=low

  * New upstream version
    - Fix smart-update failing its very first run (LP: #562496)
    - Depend on pythonX.Y-dbus and pythonX.Y-pycurl (LP: #563063)
    - Make only one request at a time to retrieve EC2 instances (LP: #567515)

  * New upstream version (LP: #557244)
    - Fix package-changer running before smart-update has completed (LP: #542215)
    - Report the version of Eucalyptus used to generate topology data (LP: #554007)
    - Enable the Eucalyptus plugin by default, if supported (LP: #546531)
    - Use a whitelist of allowed filesystem types to instead of a blacklist (LP: #351927)
    - Report the update-manager logs to the server (LP: #503384)
    - Turn off Curl's DNS caching for requests. (LP: #522668)
 -- Free Ekanayaka <email address hidden> Wed, 21 Apr 2010 12:31:28 +0200

[Andreas Hasenack (ahasenack)]

This was released already for the other distros too. A small typo in the changelog prevented it from closing this bug automatically (#522688 was referenced instead of #522668)