Add cardinality limit demonstration

Author: jack-berg

build.gradle.kts

@@ -14,11 +14,13 @@ subprojects {
 
     repositories {
         mavenCentral()
+        maven("https://oss.sonatype.org/content/repositories/snapshots")
     }
 
     dependencies {
         // using the bom ensures that all of your opentelemetry dependency versions are aligned
         implementation(platform("io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha:2.9.0-alpha"))
+        implementation(platform("io.opentelemetry:opentelemetry-bom-alpha:1.44.0-alpha-SNAPSHOT"))
     }
 
     spotless {

doc-snippets/configuration/src/main/java/otel/SdkMeterProviderConfig.java

@@ -15,11 +15,18 @@ public static SdkMeterProvider create(Resource resource) {
                 MetricReaderConfig.periodicMetricReader(
                     MetricExporterConfig.otlpHttpMetricExporter(
                         "http://localhost:4318/v1/metrics")));
+    // Uncomment to optionally register metric reader with cardinality limits
+    // builder.registerMetricReader(
+    //     MetricReaderConfig.periodicMetricReader(
+    //         MetricExporterConfig.otlpHttpMetricExporter("http://localhost:4318/v1/metrics")),
+    //     unusedInstrumentType -> 100);
+
     ViewConfig.dropMetricView(builder, "some.custom.metric");
     ViewConfig.histogramBucketBoundariesView(
         builder, "http.server.request.duration", List.of(1.0, 5.0, 10.0));
     ViewConfig.attributeFilterView(
         builder, "http.client.request.duration", Set.of("http.request.method"));
+    ViewConfig.cardinalityLimitsView(builder, "http.server.active_requests", 100);
     return builder.build();
   }
 }

doc-snippets/configuration/src/main/java/otel/ViewConfig.java

@@ -30,4 +30,11 @@ public static SdkMeterProviderBuilder attributeFilterView(
         InstrumentSelector.builder().setName(metricName).build(),
         View.builder().setAttributeFilter(keysToRetain).build());
   }
+
+  public static SdkMeterProviderBuilder cardinalityLimitsView(
+      SdkMeterProviderBuilder builder, String metricName, int cardinalityLimit) {
+    return builder.registerView(
+        InstrumentSelector.builder().setName(metricName).build(),
+        View.builder().setCardinalityLimit(cardinalityLimit).build());
+  }
 }