Allow Elasticsearch client-transport-sniff to be configured via the env

Previously, a TransportClient sniff property could not be configured
while using Spring Boot’s Elasticsearch auto-configuration. This commit
adds a new property, spring.data.elasticsearch.client-transport-sniff,
that can be used to configure the TransportClient while continuing to
use the auto-configuration support.

Closes gh-1838

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/elasticsearch/ElasticsearchAutoConfiguration.java

@@ -87,6 +87,7 @@ public class ElasticsearchAutoConfiguration implements DisposableBean {
 		TransportClientFactoryBean factory = new TransportClientFactoryBean();
 		factory.setClusterName(this.properties.getClusterName());
 		factory.setClusterNodes(this.properties.getClusterNodes());
+		factory.setClientTransportSniff(this.properties.getClientTransportSniff());
 		factory.afterPropertiesSet();
 		TransportClient client = factory.getObject();
 		this.releasable = client;

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/elasticsearch/ElasticsearchProperties.java

@@ -39,6 +39,11 @@ public class ElasticsearchProperties {
 	 */
 	private String clusterNodes;
 
+	/**
+	 * Allow the client to sniff for other members of the cluster.
+	 */
+	private boolean clientTransportSniff = true;
+
 	public String getClusterName() {
 		return this.clusterName;
 	}
@@ -54,4 +59,13 @@ public class ElasticsearchProperties {
 	public void setClusterNodes(String clusterNodes) {
 		this.clusterNodes = clusterNodes;
 	}
+
+	public boolean getClientTransportSniff() {
+		return this.clientTransportSniff;
+	}
+
+	public void setClientTransportSniff(boolean clientTransportSniff) {
+		this.clientTransportSniff = clientTransportSniff;
+	}
+
 }

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -349,6 +349,7 @@ content into your application; rather pick only the properties that you need.
 	spring.data.solr.repositories.enabled=true # if spring data repository support is enabled
 
 	# ELASTICSEARCH ({sc-spring-boot-autoconfigure}/elasticsearch/ElasticsearchProperties.{sc-ext}[ElasticsearchProperties])
+	spring.data.elasticsearch.client-transport-sniff=true # Allow the client to sniff for other members of the cluster
 	spring.data.elasticsearch.cluster-name= # The cluster name (defaults to elasticsearch)
 	spring.data.elasticsearch.cluster-nodes= # The address(es) of the server node (comma-separated; if not specified starts a client node)
 	spring.data.elasticsearch.repositories.enabled=true # if spring data repository support is enabled