public static ScaleAction ScalingLogic(
[QueueTrigger("Metrics")] Metric metric,
[Table("Scaling", "{ResourceName}", "{Name}")] ScalingStateEntity stateEntity,
[Table("Scaling", "{ResourceName}", "{Name}")] out ScalingStateEntity newStateEntity,
TraceWriter log)
{
// 1. Deserialize state
var state = stateEntity?.SerializedState != null
? JsonConvert.DeserializeObject <ScalingState>(stateEntity.SerializedState)
: new ScalingState();
var history = state.History;
log.Info($"Scaling logic: Received {metric.Name}, previous state is {string.Join(", ", history)}");
// 2. Add current metric value, remove old values
history.Add(metric.Value);
history.RemoveAll(e => e.Time < metric.Value.Time.Subtract(period));
// 3. Compare the aggregates to thresholds, produce scaling action if needed
ScaleAction action = null;
if (history.Count >= 5 &&
DateTime.Now - state.LastScalingActionTime > cooldownPeriod)
{
var average = (int)history.Average(e => e.Value);
var maximum = (int)history.Max(e => e.Value);
if (average > thresholdUp)
{
log.Info($"Scaling logic: Value {average} is too high, scaling {metric.ResourceName} up...");
state.LastScalingActionTime = DateTime.Now;
action = new ScaleAction(metric.ResourceName, ScaleActionType.Up);
}
else if (maximum < thresholdDown)
{
log.Info($"Scaling logic: Value {maximum} is low, scaling {metric.ResourceName} down...");
state.LastScalingActionTime = DateTime.Now;
action = new ScaleAction(metric.ResourceName, ScaleActionType.Down);
}
}
// 4. Serialize the state back and return the action
newStateEntity = stateEntity != null ? stateEntity : new ScalingStateEntity {
PartitionKey = metric.ResourceName, RowKey = metric.Name
};
newStateEntity.SerializedState = JsonConvert.SerializeObject(state);
return(action);
}
public static void Scaler([QueueTrigger("Actions")] ScaleAction action, TraceWriter log)
{
log.Info($"Scaler executed at: {DateTime.Now}");
var secrets = Environment.GetEnvironmentVariable("ServicePrincipal").Split(',');
var credentials = SdkContext.AzureCredentialsFactory
.FromServicePrincipal(secrets[0], secrets[1], secrets[2], AzureEnvironment.AzureGlobalCloud);
var azure = Azure.Configure()
.Authenticate(credentials)
.WithDefaultSubscription();
var plan = azure.AppServices
.AppServicePlans
.List()
.First(p => p.Name.Contains(action.ResourceName));
var newCapacity = action.Type == ScaleActionType.Down ? plan.Capacity - 1 : plan.Capacity + 1;
log.Info($"Scaler: Switching {action.ResourceName} from {plan.Capacity} {action.Type} to {newCapacity}");
plan.Update()
.WithCapacity(newCapacity)
.Apply();
}
