The case for Augeas

Kris Buytaert — Fri, 10 Jun 2011 14:26:18 +0000

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

set /augeas/load/Xml/incl[3] /tmp/blah.xml
set /augeas/load/Xml/lens Xml.lns
load
print /files/tmp/blah.xml/profile/settings/param[17]/
/files/tmp/blah.xml/profile/settings/param[17] = "#empty"
/files/tmp/blah.xml/profile/settings/param[17]/#attribute
/files/tmp/blah.xml/profile/settings/param[17]/#attribute/name = "sip-ip"
/files/tmp/blah.xml/profile/settings/param[17]/#attribute/value = "10.255.202.90"
augtool> print /files/tmp/blah.xml/profile/settings/param[18]/
/files/tmp/blah.xml/profile/settings/param[18] = "#empty"
/files/tmp/blah.xml/profile/settings/param[18]/#attribute
/files/tmp/blah.xml/profile/settings/param[18]/#attribute/name = "ext-rtp-ip"
/files/tmp/blah.xml/profile/settings/param[18]/#attribute/value = "auto-nat"
augtool> print /files/tmp/blah.xml/profile/settings/param[16]/
/files/tmp/blah.xml/profile/settings/param[16] = "#empty"
/files/tmp/blah.xml/profile/settings/param[16]/#attribute
/files/tmp/blah.xml/profile/settings/param[16]/#attribute/name = "rtp-ip"
/files/tmp/blah.xml/profile/settings/param[16]/#attribute/value = "10.255.202.90"

and get and set

augtool> get  /files/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml/profile/settings/param[17]/#attribute/value
/files/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml/profile/settings/param[17]/#attribute/value = 10.255.202.90
augtool> set /files/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml/profile/settings/param[16]/#attribute/value 10.0.0.2

Putting that into puppet however isn't that tvivial .

When you try to do this

augeas{"sipxprofile" :
        changes => [
        "set /augeas/load/Xml/incl[last()+1] /etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml",
        "set /files/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml/profile/settings/param[16]/#attribute/value 10.0.0.2",
        "set /files/etc/sipxpbx/freeswitch/conf/sip_profiles/sipX_profile.xml/profile/settings/param[17]/#attribute/value 10.0.0.2",
        ],
        }

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

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

Everything is a fine whitespace problem ...

Kris Buytaert — Mon, 02 Feb 2009 21:00:36 +0000

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.

<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.

Everything is a Freaking DNS problem - xml

The case for Augeas

Everything is a fine whitespace problem ...