Add Highway hash algorithm for client_hash

Author: surbhigarg92

google-cloud-spanner/src/main/java/com/google/cloud/spanner/BuiltInOpenTelemetryMetricsProvider.java

@@ -24,6 +24,8 @@
 import static com.google.cloud.spanner.BuiltInMetricsConstant.LOCATION_ID_KEY;
 import static com.google.cloud.spanner.BuiltInMetricsConstant.PROJECT_ID_KEY;
 
+import com.google.common.hash.HashFunction;
+import com.google.common.hash.Hashing;
 import com.google.auth.Credentials;
 import com.google.cloud.opentelemetry.detection.AttributeKeys;
 import com.google.cloud.opentelemetry.detection.DetectedPlatform;
@@ -83,8 +85,9 @@ Map<String, String> createClientAttributes(String projectId, String client_name)
     // TODO: Replace this with real value.
     clientAttributes.put(INSTANCE_CONFIG_ID_KEY.getKey(), "unknown");
     clientAttributes.put(CLIENT_NAME_KEY.getKey(), client_name);
-    clientAttributes.put(CLIENT_UID_KEY.getKey(), getDefaultTaskValue());
-    clientAttributes.put(CLIENT_HASH_KEY.getKey(), "cloud_spanner_client_raw_metrics");
+    String clientUid = getDefaultTaskValue();
+    clientAttributes.put(CLIENT_UID_KEY.getKey(), clientUid);
+    clientAttributes.put(CLIENT_HASH_KEY.getKey(), generateClientHash(clientUid));
     return clientAttributes;
   }
 
@@ -143,4 +146,15 @@ private static String getProcessId() {
       }
     }
   }
+
+  private static String generateClientHash(String clientUid) {
+    HashFunction hasher = Hashing.goodFastHash(64);
+    Long hash = hasher.hashBytes(clientUid.getBytes()).asLong();
+    return convertToHex(hash, 10);
+  }
+
+  private static String convertToHex(long hash, int kPrefixLength) {
+    long shiftedValue = hash >> (64 - kPrefixLength);
+    return String.format("%06X", shiftedValue & 0x00FFFFFFL);
+  }
 }