feat(dotnet): flatbuffers implementation of collect metrics (#84)

Author: daveleek

dotnet-engine/Yggdrasil.Engine.Tests/YggdrasilImpactMetricsTest.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Text.Json.Nodes;
 using NUnit.Framework;
 using Yggdrasil;
 
@@ -86,4 +87,17 @@ public void ImpactMetrics_Methods_Can_Be_Used_Together()
             yggdrasilEngine.ObserveHistogram("test_histogram", 0.25);
         });
     }
+
+    [Test]
+    public void CollectMetrics_Returns_Recorded_Metric()
+    {
+        var yggdrasilEngine = new YggdrasilEngine();
+        yggdrasilEngine.DefineCounter("requests_total", "Total requests");
+        Assert.DoesNotThrow(() => yggdrasilEngine.IncCounter("requests_total"));
+        var metrics = yggdrasilEngine.CollectMetricsBucket();
+        var counter = JsonNode.Parse(metrics!)!["impact_metrics"]!.AsArray()[0]!;
+        var samples = counter["samples"]!.AsArray()![0]!;
+        Assert.AreEqual("requests_total", counter["name"]!.GetValue<string>());
+        Assert.AreEqual(1, samples["value"]!.GetValue<int>());
+    }
 }

dotnet-engine/Yggdrasil.Engine/FFI.cs

@@ -28,7 +28,6 @@ static FFI()
         free_response = Marshal.GetDelegateForFunctionPointer<FreeResponseDelegate>(NativeLibLoader.LoadFunctionPointer(_libHandle, "free_response"));
 
         // everything else has some special details to it
-        // if these get out of hand they'll need some refactor but for now 5 is fine
         take_state = Marshal.GetDelegateForFunctionPointer<TakeStateDelegate>(
             NativeLibLoader.LoadFunctionPointer(_libHandle, "flat_take_state"));
 
@@ -43,6 +42,9 @@ static FFI()
 
         get_metrics = Marshal.GetDelegateForFunctionPointer<GetMetricsDelegate>(
             NativeLibLoader.LoadFunctionPointer(_libHandle, "flat_get_metrics"));
+
+        collect_metrics = Marshal.GetDelegateForFunctionPointer<CollectMetricsDelegate>(
+            NativeLibLoader.LoadFunctionPointer(_libHandle, "flat_collect_metrics"));
     }
 
     // one delegate type to rule them all, lets us not have to deal with a ton of delegate types in the higher layers
@@ -64,6 +66,9 @@ static FFI()
     [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
     private delegate Buf GetMetricsDelegate(IntPtr enginePtr);
 
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate Buf CollectMetricsDelegate(IntPtr enginePtr);
+
     [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
     private delegate IntPtr NewEngineDelegate();
 
@@ -96,6 +101,7 @@ static FFI()
     private static readonly ListKnownTogglesDelegate list_known_toggles;
     private static readonly BuiltInStrategiesDelegate built_in_strategies;
     private static readonly GetMetricsDelegate get_metrics;
+    private static readonly CollectMetricsDelegate collect_metrics;
 
     internal static Buf TakeState(IntPtr ptr, string json)
         => take_state(ptr, ToUtf8NullTerminated(json));
@@ -130,6 +136,8 @@ internal static Buf ObserveHistogram(IntPtr ptr, byte[] message)
 
     internal static Buf GetMetrics(IntPtr ptr) => get_metrics(ptr);
 
+    internal static Buf CollectMetrics(IntPtr ptr) => collect_metrics(ptr);
+
     internal static void FreeBuf(Buf buf) => free_buffer(buf);
 
     internal static IntPtr NewEngine()

dotnet-engine/Yggdrasil.Engine/Flatbuffers.cs

@@ -344,6 +344,19 @@ internal static void ParseVoidAndThrow(Buf buf)
         }
     }
 
+    internal static string GetCollectedMetricsBucket(Buf buf)
+    {
+        var response = ReadBuffer(buf);
+
+        var collectResponse = CollectMetricsResponse.GetRootAsCollectMetricsResponse(new ByteBuffer(response));
+        if (collectResponse.Error != null)
+        {
+            throw new YggdrasilEngineException(collectResponse.Error);
+        }
+
+        return collectResponse.Response;
+    }
+
     private static Dictionary<string, FeatureCount> GetMetricsFeatureCounts(MetricsResponse response)
     {
         return Enumerable.Range(0, response.TogglesLength)

dotnet-engine/Yggdrasil.Engine/YggdrasilEngine.cs

@@ -185,6 +185,12 @@ public void ObserveHistogram(string name, double value, IDictionary<string, stri
         InvokeVoid(FFI.ObserveHistogram, msg);
     }
 
+    public string? CollectMetricsBucket()
+    {
+        EnsureNotDisposed();
+        return InvokeNoMsg(FFI.CollectMetrics, Flatbuffers.GetCollectedMetricsBucket);
+    }
+
     public ICollection<FeatureDefinition> ListKnownToggles()
     {
         EnsureNotDisposed();