Add Prometheus metrics for route and 404 requests

Author: mxritzdev

LinkRouter/App/Http/Controllers/RedirectController.cs

@@ -3,6 +3,7 @@
 using LinkRouter.App.Configuration;
 using Microsoft.AspNetCore.Mvc;
 using MoonCore.Services;
+using Prometheus;
 
 namespace LinkRouter.App.Http.Controllers;
 
@@ -11,6 +12,26 @@ public class RedirectController : Controller
 {
 
     private readonly Config Config;
+    
+      
+    private readonly Counter RouteCounter = Metrics.CreateCounter(
+        "linkrouter_requests",
+        "Counts the number of requests to the link router",
+        new CounterConfiguration
+        {
+            LabelNames = new[] { "route" }
+        }
+    );
+    
+    
+    private readonly Counter NotFoundCounter = Metrics.CreateCounter(
+        "linkrouter_404_requests",
+        "Counts the number of not found requests to the link router",
+        new CounterConfiguration
+        {
+            LabelNames = new[] { "route" }
+        }
+    );
 
     public RedirectController(Config config)
     {
@@ -23,8 +44,17 @@ public IActionResult RedirectToExternalUrl(string path)
         var redirectRoute = Config.Routes.FirstOrDefault(x => x.Route == path || x.Route == path + "/" || x.Route == "/" + path);
 
         if (redirectRoute != null)
+        {
+            RouteCounter
+                .WithLabels(redirectRoute.Route)
+                .Inc();
+            
             return Redirect(redirectRoute.RedirectUrl);
+        }
 
+        NotFoundCounter
+            .WithLabels(path)
+            .Inc();
 
         if (Config.NotFoundBehavior.RedirectOn404)
             return Redirect(Config.NotFoundBehavior.RedirectUrl);
@@ -35,6 +65,10 @@ public IActionResult RedirectToExternalUrl(string path)
     [HttpGet("/")]
     public IActionResult GetRootRoute()
     {
+        RouteCounter
+            .WithLabels("/")
+            .Inc();
+        
         string url = Config.RootRoute;
 
         return Redirect(url);

LinkRouter/LinkRouter.csproj

@@ -12,6 +12,7 @@
         <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="7.0.20"/>
         <PackageReference Include="MoonCore" Version="1.5.4" />
         <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
+        <PackageReference Include="prometheus-net.AspNetCore" Version="8.2.1" />
         <PackageReference Include="Swashbuckle.AspNetCore" Version="6.5.0"/>
     </ItemGroup>
 

LinkRouter/Program.cs

@@ -6,6 +6,7 @@
 using MoonCore.Extensions;
 using MoonCore.Helpers;
 using MoonCore.Services;
+using Prometheus;
 
 namespace LinkRouter;
 
@@ -46,8 +47,14 @@ public static void Main(string[] args)
 
         builder.Services.AddSingleton(config);
 
+        builder.Services.AddMetricServer(options =>
+        {
+            options.Port = 5000;
+        });
+        
         var app = builder.Build();
 
+        app.UseMetricServer();
         app.MapControllers();
 
         app.Run();