Make Kubernetes detection slightly more efficient

See gh-19002

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/cloud/CloudPlatform.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.cloud;
 
+import java.io.File;
+
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.EnumerablePropertySource;
 import org.springframework.core.env.Environment;
@@ -77,8 +79,18 @@ public enum CloudPlatform {
 
 		private static final String SERVICE_PORT_SUFFIX = "_SERVICE_PORT";
 
+		private static final String SECRET_LOCATION = "/var/run/secrets/kubernetes.io";
+
+		private static final String KUBERNETES_SERVICE_HOST = "KUBERNETES_SERVICE_HOST";
+
+		private static final String KUBERNETES_SERVICE_PORT = "KUBERNETES_SERVICE_PORT";
+
 		@Override
 		public boolean isActive(Environment environment) {
+			if (environment.containsProperty(KUBERNETES_SERVICE_HOST)
+					|| environment.containsProperty(KUBERNETES_SERVICE_PORT) || isSecretLocationExists()) {
+				return true;
+			}
 			if (environment instanceof ConfigurableEnvironment) {
 				return isActive((ConfigurableEnvironment) environment);
 			}
@@ -107,6 +119,11 @@ public enum CloudPlatform {
 			return false;
 		}
 
+		private boolean isSecretLocationExists() {
+			File file = new File(SECRET_LOCATION);
+			return file.exists() && file.isDirectory();
+		}
+
 	};
 
 	/**

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/cloud/CloudPlatformTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.cloud;
 
+import java.io.File;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
@@ -97,6 +98,20 @@ class CloudPlatformTests {
 		assertThat(platform.isActive(environment)).isTrue();
 	}
 
+	@Test
+	void getActiveWhenHasKubernetesHostAndPortShouldReturnKubernetes() {
+		MockEnvironment environment = new MockEnvironment();
+		Map<String, Object> source = new HashMap<>();
+		source.put("KUBERNETES_SERVICE_HOST", "---");
+		source.put("KUBERNETES_SERVICE_PORT", "8080");
+		PropertySource<?> propertySource = new SystemEnvironmentPropertySource(
+				StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, source);
+		environment.getPropertySources().addFirst(propertySource);
+		CloudPlatform platform = CloudPlatform.getActive(environment);
+		assertThat(platform).isEqualTo(CloudPlatform.KUBERNETES);
+		assertThat(platform.isActive(environment)).isTrue();
+	}
+
 	@Test
 	void getActiveWhenHasServiceHostAndNoServicePortShouldNotReturnKubernetes() {
 		MockEnvironment environment = new MockEnvironment();
@@ -105,7 +120,10 @@ class CloudPlatformTests {
 				Collections.singletonMap("EXAMPLE_SERVICE_HOST", "---"));
 		environment.getPropertySources().addFirst(propertySource);
 		CloudPlatform platform = CloudPlatform.getActive(environment);
-		assertThat(platform).isNull();
+		File path = new File("/var/run/secrets/kubernetes.io");
+		if (!path.exists() && !path.isDirectory()) {
+			assertThat(platform).isNull();
+		}
 	}
 
 }