[cartservice] Record seconds instead of ticks for custom metrics

src/cart/src/cartstore/ValkeyCartStore.cs

@@ -27,15 +27,17 @@ public class ValkeyCartStore : ICartStore
 
     private static readonly ActivitySource CartActivitySource = new("OpenTelemetry.Demo.Cart");
     private static readonly Meter CartMeter = new Meter("OpenTelemetry.Demo.Cart");
-    private static readonly Histogram<long> addItemHistogram = CartMeter.CreateHistogram<long>(
+    private static readonly Histogram<double> addItemHistogram = CartMeter.CreateHistogram(
         "app.cart.add_item.latency",
-        advice: new InstrumentAdvice<long>
+        unit: "s",
+        advice: new InstrumentAdvice<double>
         {
             HistogramBucketBoundaries = [ 500000, 600000, 700000, 800000, 900000, 1000000, 1100000 ]
         });
-    private static readonly Histogram<long> getCartHistogram = CartMeter.CreateHistogram<long>(
+    private static readonly Histogram<double> getCartHistogram = CartMeter.CreateHistogram(
         "app.cart.get_cart.latency",
-        advice: new InstrumentAdvice<long>
+        unit: "s",
+        advice: new InstrumentAdvice<double>
         {
             HistogramBucketBoundaries = [ 300000, 400000, 500000, 600000, 700000, 800000, 900000 ]
         });
@@ -165,7 +167,7 @@ public async Task AddItemAsync(string userId, string productId, int quantity)
         }
         finally
         {
-            addItemHistogram.Record(stopwatch.ElapsedTicks);
+            addItemHistogram.Record(stopwatch.Elapsed.TotalSeconds);
         }
     }
 
@@ -216,7 +218,7 @@ public async Task EmptyCartAsync(string userId)
         }
         finally
         {
-            getCartHistogram.Record(stopwatch.ElapsedTicks);
+            getCartHistogram.Record(stopwatch.Elapsed.TotalSeconds);
         }
     }