From 6a61f089ce93177da4a987c28819a1fd8a5588a3 Mon Sep 17 00:00:00 2001
From: DNVindhya <DNVindhya@users.noreply.github.com>
Date: Wed, 22 Mar 2023 16:44:58 -0700
Subject: [PATCH] gcp-o11y: add default custom tag for metrics exporter

This PR adds a default custom tag for metrics, irrespective of custom
tags being present in the observability configuration.

OpenCensus by default adds a custom tag
[opencenus_task](https://docs.google.com/document/d/1sWC-XD277cM0PXxAhzJKY2X0Uj2W7bVoSv-jvnA0N8Q/edit?resourcekey=0-l-wqh1fctxZXHCUrvZv2BQ#heading=h.xy85j580eik0)
for metrics which gets overriden if custom tags are set.

The unique custom tag is required to ensure the uniqueness of the
Timeseries. The format of the default custom tag is:
`java-{PID}@{HOSTNAME}`, if `{PID}` is not available a random number
will be used.
---
 .../gcp/observability/GcpObservability.java   | 35 ++++++++++++++++---
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/gcp-observability/src/main/java/io/grpc/gcp/observability/GcpObservability.java b/gcp-observability/src/main/java/io/grpc/gcp/observability/GcpObservability.java
index 0f501da1fb1..ff5e12be399 100644
--- a/gcp-observability/src/main/java/io/grpc/gcp/observability/GcpObservability.java
+++ b/gcp-observability/src/main/java/io/grpc/gcp/observability/GcpObservability.java
@@ -51,7 +51,12 @@
 import io.opencensus.trace.Tracing;
 import io.opencensus.trace.config.TraceConfig;
 import java.io.IOException;
+import java.lang.management.ManagementFactory;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.security.SecureRandom;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
@@ -64,10 +69,13 @@ public final class GcpObservability implements AutoCloseable {
 
   private static final Logger logger = Logger.getLogger(GcpObservability.class.getName());
   private static final int METRICS_EXPORT_INTERVAL = 30;
+
+  static final String DEFAULT_METRIC_CUSTOM_TAG_KEY = "opencensus_task";
   @VisibleForTesting
   static final ImmutableSet<String> SERVICES_TO_EXCLUDE = ImmutableSet.of(
       "google.logging.v2.LoggingServiceV2", "google.monitoring.v3.MetricService",
       "google.devtools.cloudtrace.v2.TraceService");
+
   private static GcpObservability instance = null;
   private final Sink sink;
   private final ObservabilityConfig config;
@@ -199,12 +207,17 @@ void registerStackDriverExporter(String projectId, Map<String, String> customTag
       if (projectId != null) {
         statsConfigurationBuilder.setProjectId(projectId);
       }
+      Map<LabelKey, LabelValue> constantLabels = new HashMap<>();
+      constantLabels.put(
+          LabelKey.create(DEFAULT_METRIC_CUSTOM_TAG_KEY, DEFAULT_METRIC_CUSTOM_TAG_KEY),
+          LabelValue.create(generateDefaultMetricTagValue()));
       if (customTags != null) {
-        Map<LabelKey, LabelValue> constantLabels = customTags.entrySet().stream()
-            .collect(Collectors.toMap(e -> LabelKey.create(e.getKey(), e.getKey()),
-                e -> LabelValue.create(e.getValue())));
-        statsConfigurationBuilder.setConstantLabels(constantLabels);
+        for (Map.Entry<String, String> mapEntry : customTags.entrySet()) {
+          constantLabels.putIfAbsent(LabelKey.create(mapEntry.getKey(), mapEntry.getKey()),
+              LabelValue.create(mapEntry.getValue()));
+        }
       }
+      statsConfigurationBuilder.setConstantLabels(constantLabels);
       statsConfigurationBuilder.setExportInterval(Duration.create(METRICS_EXPORT_INTERVAL, 0));
       StackdriverStatsExporter.createAndRegister(statsConfigurationBuilder.build());
     }
@@ -228,6 +241,20 @@ void registerStackDriverExporter(String projectId, Map<String, String> customTag
     }
   }
 
+  private static String generateDefaultMetricTagValue() {
+    final String jvmName = ManagementFactory.getRuntimeMXBean().getName();
+    if (jvmName.indexOf('@') < 1) {
+      String hostname = "localhost";
+      try {
+        hostname = InetAddress.getLocalHost().getHostName();
+      } catch (UnknownHostException e) {
+        logger.log(Level.INFO, "Unable to get the hostname.", e);
+      }
+      return "java-" + new SecureRandom().nextInt() + "@" + hostname;
+    }
+    return "java-" + jvmName;
+  }
+
   private GcpObservability(
       Sink sink,
       ObservabilityConfig config) {