fix the default value of jute.maxbuffer in client side and an optimization for the documentation

2019-10-27 18:08:41 INFO ZooKeeper:109 - Client environment:java.io.tmpdir=/var/folders/kj/092gpj_s2hvdgx77c9ghqdv00000gp/T/
2019-10-27 18:08:41 INFO ZooKeeper:109 - Client environment:java.compiler=<NA>
2019-10-27 18:08:41 INFO ZooKeeper:109 - Client environment:os.name=Mac OS X
2019-10-27 18:08:41 INFO ZooKeeper:109 - Client environment:os.arch=x86_64
2019-10-27 18:08:41 INFO ZooKeeper:109 - Client environment:os.version=10.13.6
2019-10-27 18:08:41 INFO ZooKeeper:109 - Client environment:user.name=wenba
2019-10-27 18:08:41 INFO ZooKeeper:109 - Client environment:user.home=/Users/wenba
2019-10-27 18:08:41 INFO ZooKeeper:109 - Client environment:user.dir=/Users/wenba/workspaces/workspace_learning/YCSB
2019-10-27 18:08:41 INFO ZooKeeper:109 - Client environment:os.memory.free=234MB
2019-10-27 18:08:41 INFO ZooKeeper:109 - Client environment:os.memory.max=3641MB
2019-10-27 18:08:41 INFO ZooKeeper:109 - Client environment:os.memory.total=245MB
2019-10-27 18:08:41 INFO ZooKeeper:868 - Initiating client connection, connectString=127.0.0.1:2180/bm sessionTimeout=30000 watcher=site.ycsb.db.zookeeper.ZKClient$SimpleWatcher@4b506000
2019-10-27 18:08:41 INFO X509Util:79 - Setting -D jdk.tls.rejectClientInitiatedRenegotiation=true to disable client-initiated TLS renegotiation
2019-10-27 18:08:41 INFO ClientCnxnSocket:237 - jute.maxbuffer value is 4194304 Bytes
FAILED: Count=6, Max=106559, Min=99392, Avg=103157.33, 90=105791, 99=106559, 99.9=106559, 99.99=106559]FAILED: Count=6, Max=106559, Min=99392, Avg=103157.33, 90=105791, 99=106559, 99.9=106559, 99.99=106559]2019-10-27 18:08:51 INFO  ClientCnxn:1112 - Opening socket connection to server localhost/127.0.0.1:2180. Will not attempt to authenticate using SASL (unknown error)2019-10-27 18:08:51 INFO  ClientCnxn:959 - Socket connection established, initiating session, client: /127.0.0.1:51795, server: localhost/127.0.0.1:21802019-10-27 18:08:51 INFO  ClientCnxn:1394 - Session establishment complete on server localhost/127.0.0.1:2180, sessionid = 0x1000c6e0658000a, negotiated timeout = 300002019-10-27 18:08:51 WARN  ClientCnxn:1246 - Session 0x1000c6e0658000a for server localhost/127.0.0.1:2180, unexpected error, closing socket connection and attempting reconnectjava.io.IOException: Unreasonable length = 1073590 at org.apache.jute.BinaryInputArchive.checkLength(BinaryInputArchive.java:127) at org.apache.jute.BinaryInputArchive.readBuffer(BinaryInputArchive.java:92) at org.apache.zookeeper.proto.GetDataResponse.deserialize(GetDataResponse.java:56) at org.apache.zookeeper.ClientCnxn$SendThread.readResponse(ClientCnxn.java:919) at org.apache.zookeeper.ClientCnxnSocketNIO.doIO(ClientCnxnSocketNIO.java:101) at org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:363) at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1223)2019-10-27 18:08:51 ERROR ZKClient:128 - Error when reading a path:/user5344789772525948776,tableName:usertableorg.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss for /user5344789772525948776