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.");
}
}
internal static TableOperation CreateMetricsInsertOperation(ScaleMetrics metrics, string hostId, ScaleMonitorDescriptor descriptor, DateTime?now = null)
{
now = now ?? DateTime.UtcNow;
// Use an inverted ticks rowkey to order the table in descending order, allowing us to easily
// query for latest logs. Adding a guid as part of the key to ensure uniqueness.
string rowKey = TableStorageHelpers.GetRowKey(now.Value);
var entity = TableEntityConverter.ToEntity(metrics, hostId, rowKey, metrics.Timestamp);
entity.Properties.Add(MonitorIdPropertyName, EntityProperty.GeneratePropertyForString(descriptor.Id));
// We map the sample timestamp to its own column so it doesn't conflict with the built in column.
// We want to ensure that timestamp values for returned metrics are precise and monotonically
// increasing when ordered results are returned. The built in timestamp doesn't guarantee this.
entity.Properties.Add(SampleTimestampPropertyName, EntityProperty.GeneratePropertyForDateTimeOffset(metrics.Timestamp));
return(TableOperation.Insert(entity));
}