/// <summary>
/// Get the current scale status (vote) by querying all active monitors for their
/// scale status.
/// </summary>
/// <param name="context">The context to use for the scale decision.</param>
/// <returns>The scale vote.</returns>
public virtual async Task <ScaleStatusResult> GetScaleStatusAsync(ScaleStatusContext context)
{
var monitors = _monitorManager.GetMonitors();
List <ScaleVote> votes = new List <ScaleVote>();
if (monitors.Any())
{
// get the collection of current metrics for each monitor
var monitorMetrics = await _metricsRepository.ReadMetricsAsync(monitors);
_logger.LogDebug($"Computing scale status (WorkerCount={context.WorkerCount})");
_logger.LogDebug($"{monitorMetrics.Count} scale monitors to sample");
// for each monitor, ask it to return its scale status (vote) based on
// the metrics and context info (e.g. worker count)
foreach (var pair in monitorMetrics)
{
var monitor = pair.Key;
var metrics = pair.Value;
try
{
// create a new context instance to avoid modifying the
// incoming context
var scaleStatusContext = new ScaleStatusContext
{
WorkerCount = context.WorkerCount,
Metrics = metrics
};
var result = monitor.GetScaleStatus(scaleStatusContext);
_logger.LogDebug($"Monitor '{monitor.Descriptor.Id}' voted '{result.Vote.ToString()}'");
votes.Add(result.Vote);
}
catch (Exception exc) when(!exc.IsFatal())
{
// if a particular monitor fails, log and continue
_logger.LogError(exc, $"Failed to query scale status for monitor '{monitor.Descriptor.Id}'.");
}
}
}
else
{
// no monitors registered
// this can happen if the host is offline
}
var vote = GetAggregateScaleVote(votes, context, _logger);
return(new ScaleStatusResult
{
Vote = vote
});
}
private async Task TakeMetricsSamplesAsync()
{
try
{
// get the monitors
// if the host is offline, no monitors will be returned
var monitors = _monitorManager.GetMonitors();
if (monitors.Any())
{
_logger.LogDebug($"Taking metrics samples for {monitors.Count()} monitor(s).");
var metricsMap = new Dictionary <IScaleMonitor, ScaleMetrics>();
foreach (var monitor in monitors)
{
ScaleMetrics metrics = null;
try
{
// take a metrics sample for each monitor
metrics = await monitor.GetMetricsAsync();
metricsMap[monitor] = metrics;
// log the metrics json to provide visibility into monitor activity
var json = JsonConvert.SerializeObject(metrics);
_logger.LogDebug($"Scale metrics sample for monitor '{monitor.Descriptor.Id}': {json}");
}
catch (Exception exc) when(!exc.IsFatal())
{
// if a particular monitor fails, log and continue
_logger.LogError(exc, $"Failed to collect scale metrics sample for monitor '{monitor.Descriptor.Id}'.");
}
}
if (metricsMap.Count > 0)
{
// persist the metrics samples
await _metricsRepository.WriteMetricsAsync(metricsMap);
}
}
}
catch (Exception exc) when(!exc.IsFatal())
{
_logger.LogError(exc, "Failed to collect/persist scale metrics.");
}
}