win_perf_counters fails on counters that return no data

[nicgrobler]

Relevant telegraf.conf:

System info:

telegraf > 1.8, windows 2016, Hyper-V

Steps to reproduce:

Enable the config item for a counter that has no associated instances ("RDMA Activity", for example) on the server. the same applies to others.

Expected behavior:

Telegraf collects data from the many other counters that are valid, and do return data.

Actual behavior:

Telegraf logs an error similar to:

"E! [telegraf] Error running agent: error while getting value for counter \RDMA Activity(*)\RDMA Completion Queue Errors: No data to return."

and returns no other data.

Additional info:

Telegraf 1.8 does not behave like this - it sends for other counters.

As new to the windows agent, wanted to verify that this is a bug, and not expected (i.e. is the windows agent by design, supposed to return nothing as soon as a single input object has no data - guessing not).

The reason that we need this "fix" is because in large environments, it is a nightmare trying to change the local config on each server whenever there are no instances active (of any particular perf counter) goes away - for example, when admins are doing maintenance / playing with new features etc, they still want to be getting data from other counters.

The error is being returned from here (within the Gather func in win_perf_counters.go), two different places depending upon whether wildcardexpansion used or not:

if !isKnownCounterDataError(err) {
    return fmt.Errorf("error while getting value for counter %s: %v", metric.counterPath, err)
}

and a fix would be to simply do this:

func isKnownCounterDataError(err error) bool {
	if pdhErr, ok := err.(*PdhError); ok && (pdhErr.ErrorCode == PDH_INVALID_DATA ||
		pdhErr.ErrorCode == PDH_CALC_NEGATIVE_VALUE ||
		pdhErr.ErrorCode == PDH_CSTATUS_INVALID_DATA || 
		pdhErr.ErrorCode == PDH_NO_DATA) { -------> this line here
		return true
	}
	return false
}

obviously, this assumes that I am right about what's going on, and if the fix results in desired behaviour. If not, perhaps adding a global config flag that tells the agent to have this behaviour when desired (keep collecting and sending data for other other counters that do return data).

[glinton]

Thanks, would you mind opening a pr with your suggested fix?

[nicgrobler]

Sure, no worries

[danielnelson]

Closed in #5182