[collectd] Warning-Error of ovs_stats plugin

[Georgia Panoutsakopoulou]

Hello,

We are trying to use ovs_stats collectd’s plugin but it comes with an
error-warning and the metrics that are exposed are not stable.


We use openvswitch 2.11.0, dpdk 18.11.1 and collectd 5.9.2 (package
libyajl-dev is installed) with configuration:



<LoadPlugin ovs_stats>

   Interval 1

</LoadPlugin>



<Plugin ovs_stats>

  Port "6640"

  Address "127.0.0.1"

  Socket "/usr/local/var/run/openvswitch/db.sock"

  Bridges "fastbr0"

</Plugin>



When running collectd we get the warning:

plugin_dispatch_values: ds->type = if_errors: (ds->ds_num = 2) !=
(vl->values_len = 1)



When we tried it in debug mode the warning became an assertation error:

 assert(0 == strcmp(ds->type, vl->type)) and collectd exited.



The check that fails can be found in this link:
https://github.com/collectd/collectd/blob/master/src/daemon/plugin.c#L2121

Is there anything that we may be missing and result in this warning?



In addition, some of the metrics (e.g. ovs_stats-fastbr0.dev1/if_packets)
are not exposed constantly and sometimes, when they are exposed, their
values are NaN. Is this expected to happen or does it come as a result of
the above warning?



Note that this warning occurs when using collectd 5.9.2 and not with
collectd 5.8.1.



Thanks in advance for any help,



Georgia Panoutsakopoulou
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