SystemUsageCollectorHostedService initializes timestamp to local time but performs calculations in UTC

[foxthedream]

The constructor for SystemUsageCollectorHostedService sets a timestamp to the current process' start time. In the CollectData method we calculate the cpuTimeElapsed as DateTime.UtcNow - _lastTimeStamp, but they are in different timezones. The resulting first reading is incorrect. This is particularly evident for system clocks that are ahead of UTC and the resulting calculation is negative.

public SystemUsageCollectorHostedService(IMetrics metrics, MetricsSystemUsageCollectorOptions options)
{
    _metrics = metrics;
    _options = options;
    _lastTimeStamp = _process.StartTime;
}

private void CollectData(object state)
{
    // Lines omitted

    var cpuTimeElapsed = (DateTime.UtcNow - _lastTimeStamp).TotalMilliseconds * Environment.ProcessorCount;
    _lastTimeStamp = DateTime.UtcNow;

    // lines omitted
}

[foxthedream]

I am happy to fix the issue. I have made a fork but needed an issue number. If there is an agreement that this is a bug then I will submit a PR for it.

[alhardy]

Agree this is a bug. A PR would be great