feat: inc and dec gauge metrics

Makefile

@@ -5,3 +5,6 @@ sample:
 
 sample-clean:
  @docker compose -f docker-compose.sample.yaml down
+
+benchmark:
+ dotnet run -c Release --project ./tests/benchmark/Farfetch.LoadShedding.BenchmarkTests/Farfetch.LoadShedding.BenchmarkTests.csproj

src/Farfetch.LoadShedding.AspNetCore/Resolvers/HttpHeaderPriorityResolver.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Threading.Tasks;
 using Farfetch.LoadShedding.Tasks;
 using Microsoft.AspNetCore.Http;
@@ -9,8 +8,6 @@ internal class HttpHeaderPriorityResolver : IPriorityResolver
  {
  internal const string DefaultPriorityHeaderName = "X-Priority";
 
- private const string Separator = "-";
-
  private readonly string _headerName;
 
  public HttpHeaderPriorityResolver()
@@ -30,21 +27,7 @@ public Task<Priority> ResolveAsync(HttpContext context)
  return Task.FromResult(Priority.Normal);
  }
 
- var normalizedValue = this.NormalizeHeaderValue(values);
-
- if (!Enum.TryParse(normalizedValue, true, out Priority priority))
- {
- priority = Priority.Normal;
- }
-
- return Task.FromResult(priority);
- }
-
- private string NormalizeHeaderValue(string headerValue)
- {
- return headerValue
- .Replace(Separator, string.Empty)
- .ToLower();
+ return Task.FromResult(values.ToString().ParsePriority());
  }
  }
 }

src/Farfetch.LoadShedding.Prometheus/IAdaptativeLimiterOptionsExtensions.cs

@@ -66,9 +66,10 @@ private static void SubscribeItemDequeuedEvent(
  events.ItemDequeued.Subscribe(args =>
  {
  var method = accessor.GetMethod();
+ var priority = args.Priority.FormatPriority();
 
- queueItemsGauge.Set(method, args.Priority.FormatPriority(), args.QueueCount);
- queueTimeHistogram.Observe(method, args.Priority.FormatPriority(), args.QueueTime.TotalSeconds);
+ queueItemsGauge.Decrement(method, priority);
+ queueTimeHistogram.Observe(method, priority, args.QueueTime.TotalSeconds);
  });
  }
 
@@ -88,7 +89,7 @@ private static void SubscribeItemProcessedEvent(
  var method = accessor.GetMethod();
  var priority = args.Priority.FormatPriority();
 
- concurrencyItemsGauge.Set(method, priority, args.ConcurrencyCount);
+ concurrencyItemsGauge.Decrement(method, priority);
  taskProcessingTimeHistogram.Observe(method, priority, args.ProcessingTime.TotalSeconds);
  });
  }
@@ -123,10 +124,10 @@ private static void SubscribeItemProcessingEvent(
 
  events.ItemProcessing.Subscribe(args =>
  {
- concurrencyItemsGauge.Set(
-  accessor.GetMethod(),
- args.Priority.FormatPriority(),
-  args.ConcurrencyCount);
+ var method = accessor.GetMethod();
+ var priority = args.Priority.FormatPriority();
+
+ concurrencyItemsGauge.Increment(method, priority);
  });
  }
 
@@ -139,10 +140,10 @@ private static void SubscribeItemEnqueuedEvent(this Events.ILoadSheddingEvents e
 
  events.ItemEnqueued.Subscribe(args =>
  {
- queueItemsGauge.Set(
-  accessor.GetMethod(),
- args.Priority.FormatPriority(),
-  args.QueueCount);
+ var method = accessor.GetMethod();
+ var priority = args.Priority.FormatPriority();
+
+ queueItemsGauge.Increment(method, priority);
  });
  }
 
@@ -155,8 +156,10 @@ private static void SubscribeRejectedEvent(this Events.ILoadSheddingEvents event
 
  events.Rejected.Subscribe(args =>
  {
+ var method = accessor.GetMethod();
+
  rejectedCounter.Increment(
- accessor.GetMethod(),
+ method,
  args.Priority.FormatPriority(),
  args.Reason);
  });
@@ -171,10 +174,5 @@ private static string GetMethod(this IHttpContextAccessor accessor)
 
  return accessor.HttpContext.Request.Method.ToUpper();
  }
-
- private static string FormatPriority(this Priority priority)
- {
- return priority.ToString().ToLower();
- }
  }
 }

src/Farfetch.LoadShedding.Prometheus/Metrics/HttpRequestsConcurrencyItemsGauge.cs

@@ -1,5 +1,4 @@
 using Prometheus;
-
 using PrometheusBase = Prometheus;
 
 namespace Farfetch.LoadShedding.Prometheus.Metrics
@@ -22,16 +21,27 @@ internal HttpRequestsConcurrencyItemsGauge(
  protected override string DefaultName => "http_requests_concurrency_items_total";
 
  /// <summary>
- /// Sets the value of the gauge.
+ /// Increments the value of the gauge.
+ /// </summary>
+ /// <param name="method">The method.</param>
+ /// <param name="priority">The priority.</param>
+ public void Increment(string method, string priority)
+ {
+ this.Metric?
+ .WithLabels(method, priority)
+ .Inc();
+ }
+
+ /// <summary>
+ /// Decrements the value of the gauge.
  /// </summary>
  /// <param name="method">The method.</param>
  /// <param name="priority">The priority.</param>
- /// <param name="value">The value.</param>
- public void Set(string method, string priority, double value)
+ public void Decrement(string method, string priority)
  {
  this.Metric?
  .WithLabels(method, priority)
- .Set(value);
+ .Dec();
  }
 
  /// <inheritdoc/>
@@ -40,7 +50,7 @@ protected override Gauge Create(CollectorRegistry registry, MetricOptions option
  return PrometheusBase
  .Metrics
  .WithCustomRegistry(registry)
- .CreateGauge(options.Name, Description, new PrometheusBase.GaugeConfiguration
+ .CreateGauge(options.Name, Description, new GaugeConfiguration
  {
  LabelNames = new[] { MetricsConstants.MethodLabel, MetricsConstants.PriorityLabel },
  });

src/Farfetch.LoadShedding.Prometheus/Metrics/HttpRequestsQueueItemsGauge.cs

@@ -1,5 +1,4 @@
 using Prometheus;
-
 using PrometheusBase = Prometheus;
 
 namespace Farfetch.LoadShedding.Prometheus.Metrics
@@ -22,16 +21,27 @@ internal HttpRequestsQueueItemsGauge(
  protected override string DefaultName => "http_requests_queue_items_total";
 
  /// <summary>
- /// Sets the value of the gauge.
+ /// Increments the value of the gauge.
+ /// </summary>
+ /// <param name="method">The method.</param>
+ /// <param name="priority">The priority.</param>
+ public void Increment(string method, string priority)
+ {
+ this.Metric?
+ .WithLabels(method, priority)
+ .Inc();
+ }
+
+ /// <summary>
+ /// Decrements the value of the gauge.
  /// </summary>
  /// <param name="method">The method.</param>
  /// <param name="priority">The priority.</param>
- /// <param name="value">The value.</param>
- public void Set(string method, string priority, double value)
+ public void Decrement(string method, string priority)
  {
  this.Metric?
  .WithLabels(method, priority)
- .Set(value);
+ .Dec();
  }
 
  /// <inheritdoc/>

src/Farfetch.LoadShedding/Tasks/ConcurrentCounter.cs

@@ -64,10 +64,7 @@ public int Decrement()
  {
  lock (this._locker)
  {
- if (this._count > 0)
- {
- this._count--;
- }
+ this._count--;
 
  return this._count;
  }

src/Farfetch.LoadShedding/Tasks/PriorityExtensions.cs

@@ -0,0 +1,45 @@
+using System;
+
+namespace Farfetch.LoadShedding.Tasks
+{
+ /// <summary>
+ /// Extension methods of <see cref="Priority"/>
+ /// </summary>
+ public static class PriorityExtensions
+ {
+ /// <summary>
+ /// Parses a string value into a <see cref="Priority"/> enum.
+ /// The parser is case-insensetive and accepts hyphen. e.g. Normal, Non-Critival or CRITICAL.
+ /// </summary>
+ /// <param name="value">Priority string value to be parsed.</param>
+ /// <returns>The Priority parsed value. Returns Priority.Normal if the value is invalid.</returns>
+ public static Priority ParsePriority(this string value)
+ {
+ if (value is null)
+ {
+ return Priority.Normal;
+ }
+
+ var normalizedValue = value
+ .Replace("-", string.Empty)
+ .ToLowerInvariant();
+
+ if (Enum.TryParse(normalizedValue, true, out Priority priority))
+ {
+ return priority;
+ }
+
+ return Priority.Normal;
+ }
+
+ /// <summary>
+ /// Format a <see cref="Priority"/> enum to a string.
+ /// </summary>
+ /// <param name="priority">Priority value to be formatted.</param>
+ /// <returns>The Priority format string.</returns>
+ public static string FormatPriority(this Priority priority)
+ {
+ return priority.ToString().ToLowerInvariant();
+ }
+ }
+}

src/Farfetch.LoadShedding/Tasks/TaskQueue.cs

@@ -1,5 +1,3 @@
-using System;
-using System.Collections.Generic;
 using System.Linq;
 using System.Runtime.CompilerServices;
 
@@ -11,12 +9,7 @@ internal class TaskQueue
  {
  private readonly ConcurrentCounter _counter = new();
 
- private readonly IDictionary<Priority, TaskItemList> _queues = new SortedDictionary<Priority, TaskItemList>()
- {
- [Priority.Critical] = new TaskItemList(),
- [Priority.Normal] = new TaskItemList(),
- [Priority.NonCritical] = new TaskItemList(),
- };
+ private readonly TaskItemList[] _queues = new TaskItemList[3] { new(), new(), new() };
 
  public TaskQueue(int limit)
  {
@@ -44,9 +37,8 @@ public void Enqueue(TaskItem item)
  public TaskItem Dequeue()
  {
  var nextQueueItem = this._queues
- .FirstOrDefault(x => x.Value.HasItems)
- .Value?
- .Dequeue();
+ .FirstOrDefault(x => x.HasItems)
+ ?.Dequeue();
 
  if (nextQueueItem != null)
  {
@@ -58,7 +50,7 @@ public TaskItem Dequeue()
 
  public void Remove(TaskItem item)
  {
- if (this._queues[item.Priority].Remove(item))
+ if (this._queues[(int)item.Priority].Remove(item))
  {
  this.DecrementCounter();
  }
@@ -68,25 +60,22 @@ internal void Clear()
  {
  foreach (var queue in this._queues)
  {
- queue.Value.Clear();
+ queue.Clear();
  }
  }
 
  private int EnqueueItem(TaskItem item)
  {
- this._queues[item.Priority].Add(item);
-
- var count = this._counter.Increment();
+ this._queues[(int)item.Priority].Add(item);
 
- return count;
+ return this.IncrementCounter();
  }
 
  private void RejectLastItem()
  {
  var lastItem = this._queues
- .LastOrDefault(x => x.Value.HasItems)
- .Value?
- .DequeueLast();
+ .LastOrDefault(x => x.HasItems)
+ ?.DequeueLast();
 
  if (lastItem == null)
  {
@@ -98,9 +87,14 @@ private void RejectLastItem()
  lastItem.Reject();
  }
 
- private void DecrementCounter()
+ private int IncrementCounter()
+ {
+ return this._counter.Increment();
+ }
+
+ private int DecrementCounter()
  {
- this._counter.Decrement();
+ return this._counter.Decrement();
  }
  }
 }

tests/Directory.Build.props

@@ -2,7 +2,6 @@
  <Import Project="$([MSBuild]::GetPathOfFileAbove('Directory.Build.props', '$(MSBuildThisFileDirectory)../src'))" />
 
  <ItemGroup>
- <Compile Include="$(MSBuildProjectDirectory)/../Traits.cs" Link="Properties/Traits.cs"/>
- <AdditionalFiles Include="..\..\..\stylecop.json" Link="stylecop.json" />
+ <AdditionalFiles Include="..\..\..\stylecop.json" Link="stylecop.json" />
  </ItemGroup>
 </Project>

tests/benchmark/Farfetch.LoadShedding.BenchmarkTests/Farfetch.LoadShedding.BenchmarkTests.csproj

@@ -18,8 +18,4 @@
  <ProjectReference Include="..\..\..\src\Farfetch.LoadShedding\Farfetch.LoadShedding.csproj" />
  </ItemGroup>
 
- <ItemGroup>
- <Compile Remove="$(MSBuildProjectDirectory)/../Traits.cs" />
- </ItemGroup>
-
 </Project>