Add The Ability For The Config Client To Send All Labels To The Config Server (#2602)

docs/modules/ROOT/pages/client.adoc

@@ -133,6 +133,25 @@ Label can also be provided as a comma-separated list.
 This behavior can be useful when working on a feature branch.
 For instance, you might want to align the config label with your branch but make it optional (in that case, use `spring.cloud.config.label=myfeature,develop`).
 
+[[requesting-multiple-labels]]
+== Requesting Multiple Labels
+
+Prior to Spring Cloud Config 4.2.0, if you set `spring.cloud.config.label` to a comma-separated list of labels, the Config Client would
+try each label by making a request to the Config Server until it found one that worked.  This meant that if the first label was found, subsequent labels would not be tried.
+
+As of Spring Cloud Config 4.2.0 if you set `spring.cloud.config.label` to a comma-separated list of labels **AND** set
+`spring.cloud.config.send-all-labels` the Config Client will make a single request to the Config Server with the comma-separated list of labels
+and if **THE CONFIG SERVER IS USING VERSION 4.2.0 OR LATER** it will return a single response with property sources for all the labels.
+
+NOTE: Setting `spring.cloud-config.send-all-labels` to `true`, setting `spring.cloud.config.label` to a comma-separated list of labels,
+and using a Config Server version prior to 4.2.0 will result in unexpected behavior because the Config Server will try and find a label
+that matches the comma-separated list value and will not try and split apart the labels.
+
+By sending all labels in a single request you can reduce the number of requests made to the Config Server.
+
+`spring.cloud.config.send-all-labels` is set to `false` by default so the old behavior is still the default, and it also maintains
+compatibility with older versions of the Config Server.
+
 [[specifying-multiple-urls-for-the-config-server]]
 == Specifying Multiple URLs for the Config Server
 

spring-cloud-config-client/src/main/java/org/springframework/cloud/config/client/ConfigClientProperties.java

@@ -179,6 +179,13 @@ public class ConfigClientProperties {
 	 */
 	private Map<String, String> headers = new HashMap<>();
 
+	/**
+	 * If set to true the client will send all labels to the server instead of sending one
+	 * at a time. Support for this would require a config server version of 4.2.0 or
+	 * higher.
+	 */
+	private boolean sendAllLabels = false;
+
 	ConfigClientProperties() {
 	}
 
@@ -338,6 +345,14 @@ public class ConfigClientProperties {
 		this.headers = headers;
 	}
 
+	public boolean isSendAllLabels() {
+		return sendAllLabels;
+	}
+
+	public void setSendAllLabels(boolean sendAllLabels) {
+		this.sendAllLabels = sendAllLabels;
+	}
+
 	private Credentials extractCredentials(int index) {
 		Credentials result = new Credentials();
 		int noOfUrl = this.uri.length;
@@ -427,7 +442,7 @@ public class ConfigClientProperties {
 				+ Arrays.toString(this.uri) + ", mediaType=" + this.mediaType + ", discovery=" + this.discovery
 				+ ", failFast=" + this.failFast + ", token=" + this.token + ", requestConnectTimeout="
 				+ this.requestConnectTimeout + ", requestReadTimeout=" + this.requestReadTimeout + ", sendState="
-				+ this.sendState + ", headers=" + this.headers + "]";
+				+ this.sendState + ", headers=" + this.headers + ", sendAllLabels=" + this.sendAllLabels + "]";
 	}
 
 	/**

spring-cloud-config-client/src/main/java/org/springframework/cloud/config/client/ConfigServerConfigDataLoader.java

@@ -113,12 +113,19 @@ public class ConfigServerConfigDataLoader implements ConfigDataLoader<ConfigServ
 		Exception error = null;
 		String errorBody = null;
 		try {
-			String[] labels = new String[] { "" };
-			if (StringUtils.hasText(properties.getLabel())) {
-				labels = StringUtils.commaDelimitedListToStringArray(properties.getLabel());
+			String labelProperty = properties.getLabel();
+			String[] labels;
+			if (!properties.isSendAllLabels() && StringUtils.hasText(labelProperty)) {
+				labels = StringUtils.commaDelimitedListToStringArray(labelProperty);
+			}
+			else {
+				// This could contain a comma separated list of labels sent directly to
+				// the config server
+				// For this to work you would need to be using a config server version of
+				// 4.2.0 or later
+				labels = new String[] { StringUtils.hasText(labelProperty) ? labelProperty : "" };
 			}
 			String state = ConfigClientStateHolder.getState();
-			// Try all the labels until one works
 			for (String label : labels) {
 				Environment result = getRemoteEnvironment(context, resource, label.trim(), state);
 				if (result != null) {

spring-cloud-config-sample/src/test/java/sample/ConfigServerAndClientMultiLabelTests.java

@@ -0,0 +1,103 @@
+/*
+ * Copyright 2018-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package sample;
+
+import java.util.Map;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.actuate.autoconfigure.endpoint.web.WebEndpointProperties;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.boot.test.web.server.LocalServerPort;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.test.util.TestSocketUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+
+@SpringBootTest(classes = Application.class,
+		// Normally spring.cloud.config.enabled:true is the default but since we have the
+		// config server on the classpath we need to set it explicitly
+		// spring.config.import needs to come from orderingtest.yml to test this issue
+		// hence no spring.config.import here and config name change
+		properties = { "spring.application.name=profilesample", "spring.cloud.config.enabled=true",
+				"spring.config.name=orderingtest", "management.security.enabled=false",
+				"management.endpoints.web.exposure.include=*", "management.endpoint.env.show-values=ALWAYS",
+				"spring.cloud.config.label=label1,label2", "spring.cloud.config.send-all-labels=true" },
+		webEnvironment = RANDOM_PORT)
+public class ConfigServerAndClientMultiLabelTests {
+
+	private static final String BASE_PATH = new WebEndpointProperties().getBasePath();
+
+	private static final int configPort = TestSocketUtils.findAvailableTcpPort();
+
+	private static ConfigurableApplicationContext server;
+
+	@LocalServerPort
+	private int port;
+
+	@BeforeAll
+	public static void startConfigServer() {
+		server = SpringApplication.run(org.springframework.cloud.config.server.test.TestConfigServerApplication.class,
+				"--spring.profiles.active=native", "--server.port=" + configPort, "--spring.config.name=server");
+
+		System.setProperty("spring.cloud.config.uri", "http://localhost:" + configPort);
+	}
+
+	@AfterAll
+	public static void close() {
+		System.clearProperty("spring.cloud.config.uri");
+		if (server != null) {
+			server.close();
+		}
+	}
+
+	@Test
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	public void contextLoads() {
+		ResponseEntity<Map> response = new TestRestTemplate()
+			.getForEntity("http://localhost:" + this.port + BASE_PATH + "/env/my.prop", Map.class);
+		assertThat(response.getStatusCode()).isEqualTo(HttpStatus.OK);
+		Map res = response.getBody();
+		assertThat(res).containsKey("propertySources");
+		Map<String, Object> property = (Map<String, Object>) res.get("property");
+		assertThat(property).containsEntry("value", "my value from config server default profile");
+
+		response = new TestRestTemplate()
+			.getForEntity("http://localhost:" + this.port + BASE_PATH + "/env/my.prop.label1", Map.class);
+		assertThat(response.getStatusCode()).isEqualTo(HttpStatus.OK);
+		res = response.getBody();
+		assertThat(res).containsKey("propertySources");
+		property = (Map<String, Object>) res.get("property");
+		assertThat(property).containsEntry("value", "my value from config server label1");
+
+		response = new TestRestTemplate()
+			.getForEntity("http://localhost:" + this.port + BASE_PATH + "/env/my.prop.label2", Map.class);
+		assertThat(response.getStatusCode()).isEqualTo(HttpStatus.OK);
+		res = response.getBody();
+		assertThat(res).containsKey("propertySources");
+		property = (Map<String, Object>) res.get("property");
+		assertThat(property).containsEntry("value", "my value from config server label2");
+	}
+
+}

spring-cloud-config-sample/src/test/resources/config/label1/profilesample.yaml

@@ -0,0 +1 @@
+my.prop.label1: my value from config server label1

spring-cloud-config-sample/src/test/resources/config/label2/profilesample.yaml

@@ -0,0 +1 @@
+my.prop.label2: my value from config server label2