KAFKA-3463: change default receive buffer size for consumer to 64K

Author: Jason Gustafson <jason@confluent.io>

Reviewers: Gwen Shapira

Closes #1140 from hachikuji/KAFKA-3463

clients/src/main/java/org/apache/kafka/clients/consumer/ConsumerConfig.java

@@ -243,7 +243,7 @@ public class ConsumerConfig extends AbstractConfig {
                                         CommonClientConfigs.SEND_BUFFER_DOC)
                                 .define(RECEIVE_BUFFER_CONFIG,
                                         Type.INT,
-                                        32 * 1024,
+                                        64 * 1024,
                                         atLeast(0),
                                         Importance.MEDIUM,
                                         CommonClientConfigs.RECEIVE_BUFFER_DOC)

docs/upgrade.html

@@ -64,7 +64,7 @@ work with 0.10.0.x brokers. Therefore, 0.9.0.0 clients should be upgraded to 0.9
     is set to 0.10.0, one should not change it back to an earlier format as it may break consumers on versions before 0.10.0.0.
 </p>
 
-<h5><a id="upgrade_10_breaking" href="#upgrade_10_breaking">potential breaking changes in 0.10.0.0</a></h5>
+<h5><a id="upgrade_10_breaking" href="#upgrade_10_breaking">Potential breaking changes in 0.10.0.0</a></h5>
 <ul>
     <li> Starting from Kafka 0.10.0.0, the message format version in Kafka is represented as the Kafka version. For example, message format 0.9.0 refers to the highest message version supported by Kafka 0.9.0. </li>
     <li> Message format 0.10.0 has been introduced and it is used by default. It includes a timestamp field in the messages and relative offsets are used for compressed messages. </li>
@@ -81,6 +81,12 @@ work with 0.10.0.x brokers. Therefore, 0.9.0.0 clients should be upgraded to 0.9
     <li> The 0.7 KafkaMigrationTool is no longer packaged with Kafka. If you need to migrate from 0.7 to 0.10.0, please migrate to 0.8 first and then follow the documented upgrade process to upgrade from 0.8 to 0.10.0. </li>
 </ul>
 
+<h5><a id="upgrade_10_notable" href="#upgrade_10_notable">Notable changes in 0.10.0.0</a></h5>
+
+<ul>
+    <li> The default value of the configuration parameter <code>receive.buffer.bytes</code> is now 64K for the new consumer </li>
+</ul>
+
 <h4><a id="upgrade_9" href="#upgrade_9">Upgrading from 0.8.0, 0.8.1.X or 0.8.2.X to 0.9.0.0</a></h4>
 
 0.9.0.0 has <a href="#upgrade_9_breaking">potential breaking changes</a> (please review before upgrading) and an inter-broker protocol change from previous versions. This means that upgraded brokers and clients may not be compatible with older versions. It is important that you upgrade your Kafka cluster before upgrading your clients. If you are using MirrorMaker downstream clusters should be upgraded first as well.