Merge pull request #60 from nenoNaninu/f/custom_exception_handler

custom exception handling option

README.md

@@ -9,6 +9,7 @@ This is an [Instrumentation Library](https://github.com/open-telemetry/opentelem
 
 - [Install](#install)
 - [Usage](#usage)
+  - [Exception Handling](#exception-handling)
 - [Example](#example)
 - [Related Work](#related-work)
 
@@ -42,6 +43,27 @@ builder.Services.AddOpenTelemetry()
     });
 ```
 
+### Exception Handling
+
+By setting the `OnException` option, you can override the attributes that this library writes by default. 
+For example, when an exception occurs inside your SignalR hub method, this library sets the `otel.status_code` attribute to `ERROR`. 
+However, there are cases where you do not want a specific exception to be `ERROR`.
+In that case, you can override the default attribute by setting it as follows.
+
+```cs
+builder.Services.AddSignalR()
+    .AddHubInstrumentation(options =>
+    {
+        options.OnException = static (activity, exception) =>
+        {
+            if (exception is HubException)
+            {
+                activity.SetTag("otel.status_code", "OK");
+            }
+        };
+    });
+```
+
 ## Example
 
 The example code architecture is as follows.

src/AspNetCore.SignalR.OpenTelemetry/HubInstrumentationFilter.cs

@@ -1,20 +1,24 @@
 using System;
+using System.Diagnostics;
 using System.Threading.Tasks;
 using AspNetCore.SignalR.OpenTelemetry.Internal;
 using Microsoft.AspNetCore.Http.Connections;
 using Microsoft.AspNetCore.Http.Connections.Features;
 using Microsoft.AspNetCore.SignalR;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
 
 namespace AspNetCore.SignalR.OpenTelemetry;
 
 public sealed class HubInstrumentationFilter : IHubFilter
 {
     private readonly ILogger _logger;
+    private readonly HubInstrumentationOptions _options;
 
-    public HubInstrumentationFilter(ILoggerFactory loggerFactory)
+    public HubInstrumentationFilter(ILoggerFactory loggerFactory, IOptions<HubInstrumentationOptions> options)
     {
         _logger = loggerFactory.CreateLogger("AspNetCore.SignalR.Logging.HubLoggingFilter");
+        _options = options.Value;
     }
 
     public async ValueTask<object?> InvokeMethodAsync(
@@ -46,6 +50,9 @@ public HubInstrumentationFilter(ILoggerFactory loggerFactory)
         catch (Exception exception)
         {
             HubActivitySource.StopInvocationActivityError(activity, exception);
+
+            InvokeOptionExceptionHandler(activity, exception);
+
             throw;
         }
     }
@@ -75,6 +82,9 @@ public async Task OnConnectedAsync(HubLifetimeContext context, Func<HubLifetimeC
         catch (Exception exception)
         {
             HubActivitySource.StopInvocationActivityError(activity, exception);
+
+            InvokeOptionExceptionHandler(activity, exception);
+
             throw;
         }
     }
@@ -113,7 +123,18 @@ public async Task OnDisconnectedAsync(
         catch (Exception ex)
         {
             HubActivitySource.StopInvocationActivityError(activity, ex);
+
+            InvokeOptionExceptionHandler(activity, ex);
+
             throw;
         }
     }
+
+    private void InvokeOptionExceptionHandler(Activity? activity, Exception exception)
+    {
+        if (_options.OnException is not null && activity is not null && activity.IsAllDataRequested)
+        {
+            _options.OnException(activity, exception);
+        }
+    }
 }

src/AspNetCore.SignalR.OpenTelemetry/HubInstrumentationOptions.cs

@@ -0,0 +1,9 @@
+using System;
+using System.Diagnostics;
+
+namespace AspNetCore.SignalR.OpenTelemetry;
+
+public sealed class HubInstrumentationOptions
+{
+    public Action<Activity, Exception>? OnException { get; set; }
+}

src/AspNetCore.SignalR.OpenTelemetry/SignalRServerBuilderExtensions.cs

@@ -1,3 +1,4 @@
+using System;
 using Microsoft.AspNetCore.SignalR;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
@@ -7,6 +8,11 @@ namespace AspNetCore.SignalR.OpenTelemetry;
 public static class SignalRServerBuilderExtensions
 {
     public static ISignalRServerBuilder AddHubInstrumentation(this ISignalRServerBuilder builder)
+    {
+        return builder.AddHubInstrumentation(_ => { });
+    }
+
+    public static ISignalRServerBuilder AddHubInstrumentation(this ISignalRServerBuilder builder, Action<HubInstrumentationOptions> configure)
     {
         builder.Services.TryAddSingleton<HubInstrumentationFilter>();
 
@@ -15,6 +21,8 @@ public static ISignalRServerBuilder AddHubInstrumentation(this ISignalRServerBui
             options.AddFilter<HubInstrumentationFilter>();
         });
 
+        builder.Services.Configure(configure);
+
         return builder;
     }
 }