confusing error message and backtrace in unit agent on non-existant unit passed to relation-get

do you have a sample charm for this? there is no rel data in the topology,
so it would be interesting to test out.

On Tue, Jul 3, 2012 at 12:04 PM, Clint Byrum <email address hidden> wrote:

> Public bug reported:
>
> Test case:
>
> 1. create a charm with a relation hook which stores this yaml using
> relation-set, like this:
>
> --- begin monitors.yaml ---
> version: '0.1'
> monitors:
> nrpe:
> mysqld:
> name: MySQL Running
> args:
> command: check_procs
> args: '-c 1: /usr/sbin/mysqld'
> mysql:
> basic:
> --- end monitors.yaml ---
>
> #!/bin/sh
> relation-set something=$(cat monitors.yaml)
>
> This appears to corrupt the topology node since it is not escaped
> properly:
>
> 2012-07-03 15:17:48,451: twisted@ERROR: Unhandled Error
> Traceback (most recent call last):
> File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line
> 1181, in unwindGenerator
> return _inlineCallbacks(None, gen, Deferred())
> File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line
> 1039, in _inlineCallbacks
> result = g.send(result)
> File "/usr/lib/python2.7/dist-packages/juju/state/hook.py", line 258, in
> _setup_relation_state
> unit_id = yield self._resolve_name(unit_name)
> File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line
> 1181, in unwindGenerator
> return _inlineCallbacks(None, gen, Deferred())
> --- <exception caught here> ---
> File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line
> 1039, in _inlineCallbacks
> result = g.send(result)
> File "/usr/lib/python2.7/dist-packages/juju/state/hook.py", line 63, in
> _resolve_name
> unit_id = self._topology.get_service_unit_id_from_name(unit_name)
> File "/usr/lib/python2.7/dist-packages/juju/state/topology.py", line
> 262, in get_service_unit_id_from_name
> service_name, unit_sequence_id = unit_name.split("/")
> exceptions.ValueError: need more than 1 value to unpack
>
> ** Affects: juju
> Importance: High
> Status: New
>
> --
> You received this bug notification because you are subscribed to juju.
> https://bugs.launchpad.net/bugs/1020635
>
> Title:
> cannot store yaml in relation settings
>
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[zk: localhost:2181(CONNECTED) 38] get /relations/relation-0000000005/settings/unit-0000000001
monitors:
  monitors:
    mysql: {basic: null}
    nrpe:
      mysqld:is
        args: {args: '-c 1: /usr/sbin/mysqld', command: check_procs}
        name: MySQL Running
  version: '0.1'
private-address: ip-10-248-6-102.us-west-2.compute.internal

cZxid = 0x613

This seems wrong. We have interpreted the yaml as just an extension of the yaml, where users will expect it to just be another string of bytes.

I suspect that somewhere along the way this confuses other pieces of the code which assume only unstructured strings will come out of the relation settings.

If you deploy these:

lp:~clint-fewbar/charms/precise/mysql/add-monitors
lp:~clint-fewbar/charms/precise/nagios/add-monitors

And relate them with the add-monitors relation, the backtrace happens in nagios's unit agent.

Fully agreed.

The yaml storage, while important, is actually not the culprit here.

A bug in a hook script was running this:

relation-get monitors m

So the real bug is that this is a backtrace where it should be a simple error "unit m not found"