collection.cgi: contextswitch graph broken on Ubuntu 14.04

[mgedmin]

Problem: some of the graphs (e.g. contextswitch) do not work on Ubuntu 14.04

Apache's error.log says

collection.cgi: RRDs::graph: No DS called 'contextswitches' in '/var/lib/collectd/rrd/example.com/contextswitch/contextswitch.rrd'

Cause: collectd 5.0 changed the data schema in a backwards-incompatible way:

The convention was and is that data sets with only one data source should use the name "value" for this data source. This has been fixed for the following types:
...

• contextswitch

...

(there are 25 items in total listed there).

Complication:

The CGI script should continue to work on Ubuntu 12.04 LTS servers that have the old data schema.

Note that on upgrade to 14.04 LTS the data migration script doesn't appear to be run, so you might encounter Ubuntu 14.04 LTS servers using the old data schema. I don't mind if those become broken.

Scope:

Broken graphs that I care about are:

• contextswitch
• entropy
• ntpd
• users

[mgedmin]

The same server where I encountered the problem with contextswitch also has issues with

• entropy
• ntpd
• swap
• users

Errors from apache's error.log:

RRDs::graph: No DS called 'entropy' in '.../entropy/entropy.rrd'
RRDs::graph: No DS called 'seconds' in '.../ntpd/time_offset-error.rrd'
RRDs::graph: No DS called 'users' in '.../users/users.rrd'

and this one is especially special:

RRDs::graph: invalid rpn expression in: _nnl at /usr/lib/pov-server-page/collection.cgi line 3205.
main::meta_graph_generic_stack('HASH(0x258bbd8)', 'ARRAY(0x25dd208)') called at /usr/lib/pov-server-page/collection.cgi line 3717
main::meta_graph_swap('example.com', 'swap', undef, 'swap', undef) called at /usr/lib/pov-server-page/collection.cgi line 806
main::action_show_graph('example.com', 'swap', undef, 'swap', undef) called at /usr/lib/pov-server-page/collection.cgi line 943
main::main() called at /usr/lib/pov-server-page/collection.cgi line 65

but I have other servers running Ubuntu 14.04 that don't exhibit those problems (update: because the data schema migration script was never run on them).

[mgedmin]

Swap is missing in 14.04 OpenVZ containers due to https://bugs.launchpad.net/ubuntu/+source/collectd/+bug/1372750

[mgedmin]

I now suspect do-release-upgrade doesn't show me the debconf question asking about automated migration from collectd 4 to 5, and so I haven't actually performed the migration on any of the servers I upgraded to 14.04!

Clue: /var/cache/debconf/config.dat has

Name: collectd/auto-migrate-4-5
Template: collectd/auto-migrate-4-5
Value: false
Owners: collectd-core
Flags: seen

[mgedmin]

Heard on IRC:

mgedmin: regarding 12.04, I prepared a PPA for 5.5.0 recently: https://launchpad.net/~collectd/+archive/ubuntu/collectd-5.5

[mgedmin]

collection.cgi does not know collectd's version number.

Maybe I could add a parameter at the top and modify it during package build? But currently I build on precise and then copy the binary debs into newer Ubuntu releases.

[mgedmin]

Submitted the fix to upstream: collectd/collectd#1339