Test: allow setting socket timeout for rest client (#25221)

In #25201, a setting was added to allow setting the retry timeout for the rest client under the
impression that this would allow requests to go longer than 30s. However, there is also a socket
timeout that needs to be set to greater than 30s, which this change adds a setting for.

Author: jaymode

qa/rolling-upgrade/src/test/java/org/elasticsearch/upgrades/UpgradeClusterClientYamlTestSuiteIT.java

@@ -55,6 +55,7 @@ protected Settings restClientSettings() {
             // increase the timeout so that we can actually see the result of failed cluster health
             // calls that have a default timeout of 30s
             .put(ESRestTestCase.CLIENT_RETRY_TIMEOUT, "40s")
+            .put(ESRestTestCase.CLIENT_SOCKET_TIMEOUT, "40s")
             .build();
     }
 }

test/framework/src/main/java/org/elasticsearch/test/rest/ESRestTestCase.java

@@ -69,6 +69,7 @@ public abstract class ESRestTestCase extends ESTestCase {
     public static final String TRUSTSTORE_PATH = "truststore.path";
     public static final String TRUSTSTORE_PASSWORD = "truststore.password";
     public static final String CLIENT_RETRY_TIMEOUT = "client.retry.timeout";
+    public static final String CLIENT_SOCKET_TIMEOUT = "client.socket.timeout";
 
     /**
      * Convert the entity from a {@link Response} into a map of maps.
@@ -346,6 +347,11 @@ protected RestClient buildClient(Settings settings, HttpHost[] hosts) throws IOE
             final TimeValue maxRetryTimeout = TimeValue.parseTimeValue(requestTimeoutString, CLIENT_RETRY_TIMEOUT);
             builder.setMaxRetryTimeoutMillis(Math.toIntExact(maxRetryTimeout.getMillis()));
         }
+        final String socketTimeoutString = settings.get(CLIENT_SOCKET_TIMEOUT);
+        if (socketTimeoutString != null) {
+            final TimeValue socketTimeout = TimeValue.parseTimeValue(socketTimeoutString, CLIENT_SOCKET_TIMEOUT);
+            builder.setRequestConfigCallback(conf -> conf.setSocketTimeout(Math.toIntExact(socketTimeout.getMillis())));
+        }
         return builder.build();
     }