more refinement

Author: jack-berg

doc-snippets/prometheus-migration/src/main/java/otel/OtelUpDownCounterCallback.java

@@ -1,18 +1,27 @@
 package otel;
 
 import io.opentelemetry.api.OpenTelemetry;
+import io.opentelemetry.api.common.AttributeKey;
+import io.opentelemetry.api.common.Attributes;
 import io.opentelemetry.api.metrics.Meter;
 
 public class OtelUpDownCounterCallback {
+  private static final AttributeKey<String> DEVICE_TYPE = AttributeKey.stringKey("device_type");
+  private static final Attributes THERMOSTAT = Attributes.of(DEVICE_TYPE, "thermostat");
+  private static final Attributes LOCK = Attributes.of(DEVICE_TYPE, "lock");
+
   public static void upDownCounterCallbackUsage(OpenTelemetry openTelemetry) {
     Meter meter = openTelemetry.getMeter("smart.home");
-    // The command queue maintains its own depth counter.
+    // The device manager maintains the count of connected devices.
     // Use an asynchronous up-down counter to report that value when a MetricReader
     // collects metrics.
     meter
-        .upDownCounterBuilder("command.queue.depth")
-        .setDescription("Number of device commands waiting to be processed")
+        .upDownCounterBuilder("devices.connected")
+        .setDescription("Number of smart home devices currently connected")
         .buildWithCallback(
-            measurement -> measurement.record(SmartHomeDevices.pendingCommandCount()));
+            measurement -> {
+              measurement.record(SmartHomeDevices.connectedDeviceCount("thermostat"), THERMOSTAT);
+              measurement.record(SmartHomeDevices.connectedDeviceCount("lock"), LOCK);
+            });
   }
 }

doc-snippets/prometheus-migration/src/main/java/otel/PrometheusUpDownCounterCallback.java

@@ -4,12 +4,17 @@
 
 public class PrometheusUpDownCounterCallback {
   public static void upDownCounterCallbackUsage() {
-    // The command queue maintains its own depth counter.
+    // The device manager maintains the count of connected devices.
     // Use a callback gauge to report that value at scrape time.
     GaugeWithCallback.builder()
-        .name("command_queue_depth")
-        .help("Number of device commands waiting to be processed")
-        .callback(callback -> callback.call(SmartHomeDevices.pendingCommandCount()))
+        .name("devices_connected")
+        .help("Number of smart home devices currently connected")
+        .labelNames("device_type")
+        .callback(
+            callback -> {
+              callback.call(SmartHomeDevices.connectedDeviceCount("thermostat"), "thermostat");
+              callback.call(SmartHomeDevices.connectedDeviceCount("lock"), "lock");
+            })
         .register();
   }
 }

doc-snippets/prometheus-migration/src/main/java/otel/SmartHomeDevices.java

@@ -20,6 +20,11 @@ static double bedroomTemperatureCelsius() {
     return 0.0; // In production, this would query the device API.
   }
 
+  /** Returns the number of currently connected devices of the given type. */
+  static long connectedDeviceCount(String deviceType) {
+    return 0L; // In production, this would query the device manager.
+  }
+
   /** Returns the number of device commands currently waiting to be processed. */
   static long pendingCommandCount() {
     return 0L; // In production, this would query the command queue.