$ echo srvr | nc localhost 2181

$ echo srvr | nc localhost 2181

Zookeeper version: 3.3.3-1203054, built on 11/17/2011 05:47 GMT

Latency min/avg/max: 0/0/82

Received: 70940852

Sent: 71197941

Outstanding: 1

Zxid: 0x2000016bf

Mode: follower

Node count: 4325

$ echo srvr | nc localhost 2181 | grep Mode

Mode: leader

$ echo stat | nc localhost 2181

Zookeeper version: 3.3.3-1203054, built on 11/17/2011 05:47 GMT

Clients:

...

Latency min/avg/max: 0/0/16

Received: 4288

Sent: 4288

Outstanding: 0

Zxid: 0x1007f3e40

Mode: follower

Node count: 4317

$ echo ruok | nc 127.0.0.1 2181

imok

$ echo envi | nc 127.0.0.1 2181

$ echo dump | nc 127.0.0.1 2181

SessionTracker dump:

org.apache.zookeeper.server.quorum.LearnerSessionTracker@63f69aa9

ephemeral nodes dump:

Sessions with Ephemerals (225):

0x54f9dca900afb7f:

/google/plus/real/monitor/n_0000000040

.....

$ wget https://raw.githubusercontent.com/phunt/zktop/master/zktop.py

$ chmod 755 zktop.py

$ ./zktop.py --server "a.google.com:2181,b.google.com:2181,c.google.com:2181"

$ ./zkCli.sh

> rmr /node

2016-08-02 20:49:27,597 FATAL [Samuelui-MacBook-Pro:59298.activeMasterManager] master.HMaster: Failed to become active master

java.net.ConnectException: Call From Samuelui-MacBook-Pro.local/1.1.1.1 to localhost:9000 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.lang.reflect.Constructor.newInstance(Constructor.java:422)

at org.apache.hadoop.net.NetUtils.wrapWithMessage(NetUtils.java:783)

at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:730)

at org.apache.hadoop.ipc.Client.call(Client.java:1415)

at org.apache.hadoop.ipc.Client.call(Client.java:1364)

at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:206)

at com.sun.proxy.$Proxy16.setSafeMode(Unknown Source)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:497)

at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:187)

at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)

at com.sun.proxy.$Proxy16.setSafeMode(Unknown Source)

at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.setSafeMode(ClientNamenodeProtocolTranslatorPB.java:602)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:497)

at org.apache.hadoop.hbase.fs.HFileSystem$1.invoke(HFileSystem.java:279)

at com.sun.proxy.$Proxy17.setSafeMode(Unknown Source)

at org.apache.hadoop.hdfs.DFSClient.setSafeMode(DFSClient.java:2264)

at org.apache.hadoop.hdfs.DistributedFileSystem.setSafeMode(DistributedFileSystem.java:986)

at org.apache.hadoop.hdfs.DistributedFileSystem.setSafeMode(DistributedFileSystem.java:970)

at org.apache.hadoop.hbase.util.FSUtils.isInSafeMode(FSUtils.java:525)

at org.apache.hadoop.hbase.util.FSUtils.waitOnSafeMode(FSUtils.java:971)

at org.apache.hadoop.hbase.master.MasterFileSystem.checkRootDir(MasterFileSystem.java:424)

at org.apache.hadoop.hbase.master.MasterFileSystem.createInitialFileSystemLayout(MasterFileSystem.java:153)

at org.apache.hadoop.hbase.master.MasterFileSystem.<init>(MasterFileSystem.java:128)

at org.apache.hadoop.hbase.master.HMaster.finishActiveMasterInitialization(HMaster.java:638)

at org.apache.hadoop.hbase.master.HMaster.access$500(HMaster.java:184)

at org.apache.hadoop.hbase.master.HMaster$1.run(HMaster.java:1729)

at java.lang.Thread.run(Thread.java:745)

Caused by: java.net.ConnectException: Connection refused

at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)

at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)

at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)

at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:529)

at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:493)

at org.apache.hadoop.ipc.Client$Connection.setupConnection(Client.java:606)

at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:700)

at org.apache.hadoop.ipc.Client$Connection.access$2800(Client.java:367)

at org.apache.hadoop.ipc.Client.getConnection(Client.java:1463)

at org.apache.hadoop.ipc.Client.call(Client.java:1382)

... 29 more

2016-08-03 10:53:19,227 DEBUG [main-SendThread(fe80:0:0:0:0:0:0:1%1:2181)] zookeeper.ClientCnxnSocketNIO: Ignoring exception during shutdown input

java.net.SocketException: Socket is not connected

        at sun.nio.ch.Net.translateToSocketException(Net.java:145)

        at sun.nio.ch.Net.translateException(Net.java:179)

        at sun.nio.ch.Net.translateException(Net.java:185)

        at sun.nio.ch.SocketAdaptor.shutdownInput(SocketAdaptor.java:404)

        at org.apache.zookeeper.ClientCnxnSocketNIO.cleanup(ClientCnxnSocketNIO.java:200)

        at org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1185)

        at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1110)

Caused by: java.nio.channels.NotYetConnectedException

        at sun.nio.ch.SocketChannelImpl.shutdownInput(SocketChannelImpl.java:782)

        at sun.nio.ch.SocketAdaptor.shutdownInput(SocketAdaptor.java:402)

        ... 3 more

2016-08-02 16:07:11,339 WARN  [RS:0;172.26.116.174:50808-SendThread(fe80:0:0:0:0:0:0:1%1:2181)] zookeeper.ClientCnxn: Session 0x1564a13ad290003 for server null, unexpected error, closing socket connection and attempting reconnect

java.net.ConnectException: Connection refused

at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)

at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)

at org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:361)

at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1081)

        MonitoredTask status = TaskMonitor.get().createStatus("Master startup");

        status.setDescription("Master startup");

        try {

          if (activeMasterManager.blockUntilBecomingActiveMaster(timeout, status)) {

            finishActiveMasterInitialization(status);

          }

        } catch (Throwable t) {

          status.setStatus("Failed to become active: " + t.getMessage());

          LOG.fatal("Failed to become active master", t);

          // HBASE-5680: Likely hadoop23 vs hadoop 20.x/1.x incompatibility

          if (t instanceof NoClassDefFoundError &&

              t.getMessage().contains("org/apache/hadoop/hdfs/protocol/FSConstants$SafeModeAction")) {

            // improved error message for this special case

            abort("HBase is having a problem with its Hadoop jars.  You may need to "

              + "recompile HBase against Hadoop version "

              +  org.apache.hadoop.util.VersionInfo.getVersion()

              + " or change your hadoop jars to start properly", t);

          } else {

            abort("Unhandled exception. Starting shutdown.", t);

          }

        } finally {

          status.cleanup();

        }

 <property>

    <name>hbase.rootdir</name>

    <value>/tmp/hbase/data</value>

  </property>

 <property>

    <name>hbase.rootdir</name>

    <value>file:///tmp/hbase/data</value>

  </property>

$ ls  .cassandra/

cli.history  cqlsh_history  nodetool.history

$ ./cqlsh

Connected to Test Cluster at 127.0.0.1:9042.

[cqlsh 5.0.1 | Cassandra 2.1.10 | CQL spec 3.2.1 | Native protocol v3]

Use HELP for help.

cqlsh>

cqlsh>

cqlsh> CREATE KEYSPACE test WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1 } ;

cqlsh> use test ;

cqlsh:test> CREATE TABLE foo (name text, age int, pet text, primary key (name)) ;

cqlsh:test> insert into foo (name, age, pet) values ('yves', 81, 'german shepherd') ;

cqlsh:test> insert into foo (name, pet) values ('coco', 'ferret') ;

cqlsh:test> SELECT * FROM foo ;

 name | age  | pet

------+------+-----------------

 coco | null |          ferret

 yves |   81 | german shepherd

cqlsh:test> SELECT * FROM foo WHERE age=null;

InvalidRequest: code=2200 [Invalid query] message="Unsupported null value for indexed column age"

 CONTROL  [initandlisten] ** WARNING: soft rlimits too low. rlimits set to 31394 processes, 1024000 files. Number of processes should be at least 512000 : 0.5 times number of files.

*       soft    nproc   1024000

*       hard    nproc   1024000

Recommended ulimit Settings

Every deployment may have unique requirements and settings; however, the following thresholds and settings are particularly important for mongod and mongos deployments:

• -f (file size): unlimited
• -t (cpu time): unlimited
• -v (virtual memory): unlimited [1]
• -n (open files): 64000
• -m (memory size): unlimited [1] [2]
• -u (processes/threads): 64000