riemann-net: Initial packet drop not reported as warning

[sslavic]

Issue

What's the issue...?
If there are packets dropped on boot, riemann-net will measure dropped packets count as initial value, but since there's no old/previous value, warning will not be reported.

I believe https://github.com/riemann/riemann-tools/blob/master/bin/riemann-net#L77
should be replaced with something like

    if not @old_state.has_key?(service)
      @old_state[service] = 0
    end

What's your riemann-tools version?

0.2.6 but same logic is on trunk

What platform are you on?

Ubuntu 14.04.5 LTS (GNU/Linux 4.4.0-66-generic x86_64)

[jamtur01]

Seems reasonable - happy to take a patch on this.

[smortex]

I feel concerned about this one: if a system has a non-zero error count, each time riemann-net start it will send a critical event. So a single error can end up reported multiple times, which is not good, and I think worse that not reporting an error that happened in the past.

Also, beyond the error metrics, and because they are rates, the initial value when riemann-net restart will be wrong (because the value is divided by the interval, and instead of a count from the last event, the value is a count from system boot). Adjusting this special case to divide by the system uptime is also likely to create a metric which is multiple orders of magnitude offset to the actual rate at the time riemann-net started.

So the current behavior of not sending the first batch of events seems a sensible choice.