Jun 10 2011

The case for Augeas

Ever since I met David Lutterkort over steaks at OLS 2007 augeas was this tool in the back of my mind that I couldn't place... I never saw the need for it... or it seemed to be huge overkill for the problem that needed solving .

Till I ran into sipxecs rewriting XML files on the fly .. and putting values in their XML that I could not trace back to an original source. As of Augeas 0.8.x there's an XML lens out there.

Digging innot blah.xml with augtool you can do stuff like

  1. set /augeas/load/Xml/incl[3] /tmp/blah.xml
  2. set /augeas/load/Xml/lens Xml.lns
  3. load
  4. print /files/tmp/blah.xml/profile/settings/param[17]/
  5. /files/tmp/blah.xml/profile/settings/param[17] = "#empty"
  6. /files/tmp/blah.xml/profile/settings/param[17]/#attribute
  7. /files/tmp/blah.xml/profile/settings/param[17]/#attribute/name = "sip-ip"
  8. /files/tmp/blah.xml/profile/settings/param[17]/#attribute/value = ""
  9. augtool> print /files/tmp/blah.xml/profile/settings/param[18]/
  10. /files/tmp/blah.xml/profile/settings/param[18] = "#empty"
  11. /files/tmp/blah.xml/profile/settings/param[18]/#attribute
  12. /files/tmp/blah.xml/profile/settings/param[18]/#attribute/name = "ext-rtp-ip"
  13. /files/tmp/blah.xml/profile/settings/param[18]/#attribute/value = "auto-nat"
  14. augtool> print /files/tmp/blah.xml/profile/settings/param[16]/
  15. /files/tmp/blah.xml/profile/settings/param[16] = "#empty"
  16. /files/tmp/blah.xml/profile/settings/param[16]/#attribute
  17. /files/tmp/blah.xml/profile/settings/param[16]/#attribute/name = "rtp-ip"
  18. /files/tmp/blah.xml/profile/settings/param[16]/#attribute/value = ""

and get and set

  1. augtool> get /files/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml/profile/settings/param[17]/#attribute/value
  2. /files/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml/profile/settings/param[17]/#attribute/value =
  3. augtool> set /files/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml/profile/settings/param[16]/#attribute/value

Putting that into puppet however isn't that tvivial .

When you try to do this

  1. augeas{"sipxprofile" :
  2. changes => [
  3. "set /augeas/load/Xml/incl[last()+1] /etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml",
  4. "set /files/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml/profile/settings/param[16]/#attribute/value",
  5. "set /files/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml/profile/settings/param[17]/#attribute/value",
  6. ],
  7. }

Puppet really doesn't output what you want to do ... it only outputs the snippet you modify ..
It's the load statement above that is the really important piece but puppet can't directly work with that so you need to go around that using
The way to solve this is

  1. augeas{"sipxprofile" :
  2. lens => "Xml.lns",
  3. incl => "/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml",
  4. context => "/files/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml",
  5. changes => [
  6. "set profile/settings/param[16]/#attribute/value $ipaddress",
  7. "set profile/settings/param[17]/#attribute/value $ipaddress",
  8. ],
  9. onlyif => "get profile/settings/param[16]/#attribute/value != $ipaddress",
  10. }

Feb 02 2009

Everything is a fine whitespace problem ...

Couple of days ago I was working on a Linux Heartbeat v2 setup.
Upon inserting an XML snippet into the cib cib-adm started eating memory fast until the oom killer kicked in.

The environment was running a fairly old heartbeat-2.0.8 version so I upgraded to heartbeat-2.1.4-2.1 and there I got a nice warning that my XML sintax wasn't correct.

There was a whitespace in the XML syntax.

  1. <expression attribute="#replicationvalue" id="is_lagged" operation ="gt" ... ><

Removing the whitespace solves the problem, also on the older version. So the problem is already fixed upstream.. but you might run into it anyhow.