1.2.2. Get Started with HBase

1. For HBase 0.98.5 and later, you are required to set the JAVA_HOME environment variable before starting HBase. Prior to 0.98.5, HBase attempted to detect the location of Java if the variables was not set. You can set the variable via your operating system‘s usual mechanism, but HBase provides a central mechanism,conf/hbase-env.sh. Edit this file, uncomment the line starting with JAVA_HOME, and set it to the appropriate location for your operating system. The JAVA_HOME variable should be set to a directory which contains the executable file bin/java. Most modern Linux operating systems provide a mechanism, such as /usr/bin/alternatives on RHEL or CentOS, for transparently switching between versions of executables such as Java. In this case, you can set JAVA_HOME to the directory containing the symbolic link to bin/java, which is usually /usr.

   JAVA_HOME=/usr

2. Edit main HBase configuration file conf/hbase-site.xml. At this time, only need to specify the directory on the local filesystem where HBase and Zookeeper write data. By default, a new directory is created under /tmp. Many servers are configured to delete the contents of /tmp upon reboot, so you should store the data elsewhere. The following configuration will store HBase‘s data in the hbase directory, in the home directory of the user called testuser. Paste the<property> tags beneath the <configuration> tags, which should be empty in a new HBase install.

3.  Example hbase-site.xml for Standalone HBase

   <configuration>  <property>    <name>hbase.rootdir</name>    <value>file:///home/testuser/hbase</value>                              //hbase是用户为存储数据而建立的一个目录  </property>  <property>                                                                //我还没有安装zookeeper，所以没有这部分的配置信息    <name>hbase.zookeeper.property.dataDir</name>    <value>/home/testuser/zookeeper</value>  </property></configuration>                

4. The bin/start-hbase.sh script is provided as a convenient way to start HBase. Issue the command, and if all goes well, a message is logged to standard output showing that HBase started successfully. You can use the jps command to verify that you have one running process called HMaster. In standalone mode HBase runs all daemons within this single JVM, i.e. the HMaster, a single HRegionServer, and the ZooKeeper daemon.

Procedure 1.2. Use HBase For the First Time

1. Connect to HBase.

   $ ./bin/hbase shellhbase(main):001:0> 
   

2. Display HBase Shell Help Text.

   Type help and press Enter, to display some basic usage information for HBase Shell, as well as several example commands.

3. Create a table.

    You must specify the table name and the ColumnFamily name.

   hbase> create ‘test‘, ‘cf‘    0 row(s) in 1.2200 seconds        

4. List Information About your Table

   hbase> list ‘test‘TABLEtest1 row(s) in 0.0350 seconds=> ["test"]

5. Put data into your table.

   hbase> put ‘test‘, ‘row1‘, ‘cf:a‘, ‘value1‘0 row(s) in 0.1770 secondshbase> put ‘test‘, ‘row2‘, ‘cf:b‘, ‘value2‘0 row(s) in 0.0160 secondshbase> put ‘test‘, ‘row3‘, ‘cf:c‘, ‘value3‘0 row(s) in 0.0260 seconds          

6. Scan the table for all data at once.

   hbase> scan ‘test‘ROW                   COLUMN+CELL row1                 column=cf:a, timestamp=1403759475114, value=http://www.mamicode.com/value1>

7. Get a single row of data.

   hbase> get ‘test‘, ‘row1‘COLUMN                CELL cf:a                 timestamp=1403759475114, value=http://www.mamicode.com/value1>

8. Disable a table.

   If you want to delete a table or change its settings, as well as in some other situations, you need to disable the table first, using the disable command. You can re-enable it using the enable command.

   hbase> disable ‘test‘0 row(s) in 1.6270 secondshbase> enable ‘test‘0 row(s) in 0.4500 seconds

   hbase> disable ‘test‘0 row(s) in 1.6270 seconds                      

9. Drop the table.

   hbase> drop ‘test‘0 row(s) in 0.2900 seconds                      

10. Exit the HBase Shell.

    To exit the HBase Shell and disconnect from your cluster, use the quit command. 

11.  Stop HBase

1. $ ./bin/stop-hbase.shstopping hbase....................$

1.2.3. Intermediate - Pseudo-Distributed Local Install

Hadoop Configuration

This procedure assumes that you have configured Hadoop and HDFS on your local system and or a remote system, and that they are running and available. It also assumes you are using Hadoop 2. Currently, the documentation on the Hadoop website does not include a quick start for Hadoop 2, but the guide athttp://www.alexjf.net/blog/distributed-systems/hadoop-yarn-installation-definitive-guide is a good starting point.

1. Stop HBase if it is running.

   If you have just finished Section 1.2, “Quick Start - Standalone HBase” and HBase is still running, stop it. This procedure will create a totally new directory where HBase will store its data, so any databases you created before will be lost.

2. Configure HBase.

   Edit the hbase-site.xml configuration. First, add the following property. which directs HBase to run in distributed mode, with one JVM instance per daemon.

   <property>  <name>hbase.cluster.distributed</name>  <value>true</value></property>            

   Next, change the hbase.rootdir from the local filesystem to the address of your HDFS instance, using the hdfs://// URI syntax. In this example, HDFS is running on the localhost at port 8020.

   <property>  <name>hbase.rootdir</name>  <value>hdfs://localhost:8020/hbase</value></property>                                  

   You do not need to create the directory in HDFS. HBase will do this for you. If you create the directory, HBase will attempt to do a migration, which is not what you want.

3. Start HBase.

   Use the bin/start-hbase.sh command to start HBase. If your system is configured correctly, the jps command should show the HMaster and HRegionServer processes running.

4. Check the HBase directory in HDFS.

   If everything worked correctly, HBase created its directory in HDFS. In the configuration above, it is stored in /hbase/ on HDFS. You can use the hadoop fscommand in Hadoop‘s bin/ directory to list this directory.

   $ ./bin/hadoop fs -ls /hbaseFound 7 itemsdrwxr-xr-x   - hbase users          0 2014-06-25 18:58 /hbase/.tmpdrwxr-xr-x   - hbase users          0 2014-06-25 21:49 /hbase/WALsdrwxr-xr-x   - hbase users          0 2014-06-25 18:48 /hbase/corruptdrwxr-xr-x   - hbase users          0 2014-06-25 18:58 /hbase/data-rw-r--r--   3 hbase users         42 2014-06-25 18:41 /hbase/hbase.id-rw-r--r--   3 hbase users          7 2014-06-25 18:41 /hbase/hbase.versiondrwxr-xr-x   - hbase users          0 2014-06-25 21:49 /hbase/oldWALs          

5. Create a table and populate it with data.

   You can use the HBase Shell to create a table, populate it with data, scan and get values from it, using the same procedure as in Procedure 1.2, “Use HBase For the First Time”.

6. Start and stop a backup HBase Master (HMaster) server.

   Note

   Running multiple HMaster instances on the same hardware does not make sense in a production environment, in the same way that running a pseudo-distributed cluster does not make sense for production. This step is offered for testing and learning purposes only.

   The HMaster server controls the HBase cluster. You can start up to 9 backup HMaster servers, which makes 10 total HMasters, counting the primary. To start a backup HMaster, use the local-master-backup.sh. For each backup master you want to start, add a parameter representing the port offset for that master. Each HMaster uses three ports (16010, 16020, and 16030 by default). The port offset is added to these ports, so using an offset of 2, the backup HMaster would use ports 16012, 16022, and 16032. The following command starts 3 backup servers using ports 16012/16022/16032, 16013/16023/16033, and 16015/16025/16035.

   $ ./bin/local-master-backup.sh 2 3 5                         

   To kill a backup master without killing the entire cluster, you need to find its process ID (PID). The PID is stored in a file with a name like /tmp/hbase-USER-X-master.pid. The only contents of the file are the PID. You can use the kill -9 command to kill that PID. The following command will kill the master with port offset 1, but leave the cluster running:

   $ cat /tmp/hbase-testuser-1-master.pid |xargs kill -9                      

7. Start and stop additional RegionServers

   The HRegionServer manages the data in its StoreFiles as directed by the HMaster. Generally, one HRegionServer runs per node in the cluster. Running multiple HRegionServers on the same system can be useful for testing in pseudo-distributed mode. The local-regionservers.sh command allows you to run multiple RegionServers. It works in a similar way to the local-master-backup.sh command, in that each parameter you provide represents the port offset for an instance. Each RegionServer requires two ports, and the default ports are 16020 and 16030. However, the base ports for additional RegionServers are not the default ports since the default ports are used by the HMaster, which is also a RegionServer since HBase version 1.0.0. The base ports are 16200 and 16300 instead. You can run 99 additional RegionServers that are not a HMaster or backup HMaster, on a server. The following command starts four additional RegionServers, running on sequential ports starting at 16202/16302 (base ports 16200/16300 plus 2).

   $ .bin/local-regionservers.sh start 2 3 4 5                      

   To stop a RegionServer manually, use the local-regionservers.sh command with the stop parameter and the offset of the server to stop.

   $ .bin/local-regionservers.sh stop 3

8. Stop HBase.

   You can stop HBase the same way as in the Section 1.2, “Quick Start - Standalone HBase” procedure, using the bin/stop-hbase.sh command.

1.2.4. Advanced - Fully Distributed

Table 1.1. Distributed Cluster Demo Architecture

Note

Be sure that all the nodes have full access to communicate, and that no firewall rules are in place which could prevent them from talking to each other. If you see any errors like no route to host, check your firewall.

Procedure 1.4. Configure Password-Less SSH Access

node-a needs to be able to log into node-b and node-c (and to itself) in order to start the daemons. The easiest way to accomplish this is to use the same username on all hosts, and configure password-less SSH login from node-a to each of the others.

1. On node-a, generate a key pair.

   While logged in as the user who will run HBase, generate a SSH key pair, using the following command:

   $ ssh-keygen -t rsa

   If the command succeeds, the location of the key pair is printed to standard output. The default name of the public key is id_rsa.pub.

2. Create the directory that will hold the shared keys on the other nodes.

   On node-b and node-c, log in as the HBase user and create a .ssh/ directory in the user‘s home directory, if it does not already exist. If it already exists, be aware that it may already contain other keys.

3. Copy the public key to the other nodes.

   Securely copy the public key from node-a to each of the nodes, by using the scp or some other secure means. On each of the other nodes, create a new file called.ssh/authorized_keys if it does not already exist, and append the contents of the id_rsa.pub file to the end of it. Note that you also need to do this for node-aitself.

   $ cat id_rsa.pub >> ~/.ssh/authorized_keys

4. Test password-less login.

   If you performed the procedure correctly, if you SSH from node-a to either of the other nodes, using the same username, you should not be prompted for a password.

5. Since node-b will run a backup Master, repeat the procedure above, substituting node-b everywhere you see node-a. Be sure not to overwrite your existing.ssh/authorized_keys files, but concatenate the new key onto the existing file using the >> operator rather than the > operator.

Procedure 1.5. Prepare node-a

node-a will run your primary master and ZooKeeper processes, but no RegionServers.

1. Stop the RegionServer from starting on node-a.

   Edit conf/regionservers and remove the line which contains localhost. Add lines with the hostnames or IP addresses for node-b and node-c. Even if you did want to run a RegionServer on node-a, you should refer to it by the hostname the other servers would use to communicate with it. In this case, that would be node-a.example.com. This enables you to distribute the configuration to each node of your cluster any hostname conflicts. Save the file.

2. Configure HBase to use node-b as a backup master.

   Create a new file in conf/ called backup-masters, and add a new line to it with the hostname for node-b. In this demonstration, the hostname is node-b.example.com.

3. Configure ZooKeeper

   In reality, you should carefully consider your ZooKeeper configuration. You can find out more about configuring ZooKeeper in Chapter 20, ZooKeeper. This configuration will direct HBase to start and manage a ZooKeeper instance on each node of the cluster.

   On node-a, edit conf/hbase-site.xml and add the following properties.

   <property>  <name>hbase.zookeeper.quorum</name>  <value>node-a.example.com,node-b.example.com,node-c.example.com</value></property><property>  <name>hbase.zookeeper.property.dataDir</name>  <value>/usr/local/zookeeper</value></property>                        

4. Everywhere in your configuration that you have referred to node-a as localhost, change the reference to point to the hostname that the other nodes will use to refer to node-a. In these examples, the hostname is node-a.example.com.

Procedure 1.6. Prepare node-b and node-c

node-b will run a backup master server and a ZooKeeper instance.

1. Download and unpack HBase.

   Download and unpack HBase to node-b, just as you did for the standalone and pseudo-distributed quickstarts.

2. Copy the configuration files from node-a to node-b.and node-c.

   Each node of your cluster needs to have the same configuration information. Copy the contents of the conf/ directory to the conf/ directory on node-b and node-c.

Procedure 1.7. Start and Test Your Cluster

1. Be sure HBase is not running on any node.

   If you forgot to stop HBase from previous testing, you will have errors. Check to see whether HBase is running on any of your nodes by using the jps command. Look for the processes HMaster, HRegionServer, and HQuorumPeer. If they exist, kill them.

2. Start the cluster.

   On node-a, issue the start-hbase.sh command. Your output will be similar to that below.

   $ bin/start-hbase.shnode-c.example.com: starting zookeeper, logging to /home/hbuser/hbase-0.98.3-hadoop2/bin/../logs/hbase-hbuser-zookeeper-node-c.example.com.outnode-a.example.com: starting zookeeper, logging to /home/hbuser/hbase-0.98.3-hadoop2/bin/../logs/hbase-hbuser-zookeeper-node-a.example.com.outnode-b.example.com: starting zookeeper, logging to /home/hbuser/hbase-0.98.3-hadoop2/bin/../logs/hbase-hbuser-zookeeper-node-b.example.com.outstarting master, logging to /home/hbuser/hbase-0.98.3-hadoop2/bin/../logs/hbase-hbuser-master-node-a.example.com.outnode-c.example.com: starting regionserver, logging to /home/hbuser/hbase-0.98.3-hadoop2/bin/../logs/hbase-hbuser-regionserver-node-c.example.com.outnode-b.example.com: starting regionserver, logging to /home/hbuser/hbase-0.98.3-hadoop2/bin/../logs/hbase-hbuser-regionserver-node-b.example.com.out            node-b.example.com: starting master, logging to /home/hbuser/hbase-0.98.3-hadoop2/bin/../logs/hbase-hbuser-master-nodeb.example.com.out                    

   ZooKeeper starts first, followed by the master, then the RegionServers, and finally the backup masters.

3. Verify that the processes are running.

   On each node of the cluster, run the jps command and verify that the correct processes are running on each server. You may see additional Java processes running on your servers as well, if they are used for other purposes.

   Example 1.3. node-a jps Output

   $ jps20355 Jps20071 HQuorumPeer20137 HMaster                

   
   

   Example 1.4. node-b jps Output

   $ jps15930 HRegionServer16194 Jps15838 HQuorumPeer16010 HMaster                        

   
   

   Example 1.5. node-c jps Output

   $ jps    13901 Jps13639 HQuorumPeer13737 HRegionServer            

   
   

   ZooKeeper Process Name

   The HQuorumPeer process is a ZooKeeper instance which is controlled and started by HBase. If you use ZooKeeper this way, it is limited to one instance per cluster node, , and is appropriate for testing only. If ZooKeeper is run outside of HBase, the process is called QuorumPeer. For more about ZooKeeper configuration, including using an external ZooKeeper instance with HBase, see Chapter 20, ZooKeeper.

4. Browse to the Web UI.

   Web UI Port Changes

   In HBase newer than 0.98.x, the HTTP ports used by the HBase Web UI changed from 60010 for the Master and 60030 for each RegionServer to 16610 for the Master and 16030 for the RegionServer.

   If everything is set up correctly, you should be able to connect to the UI for the Master http://node-a.example.com:60110/ or the secondary master at http://node-b.example.com:60110/ for the secondary master, using a web browser. If you can connect via localhost but not from another host, check your firewall rules. You can see the web UI for each of the RegionServers at port 60130 of their IP addresses, or by clicking their links in the web UI for the Master.

5. Test what happens when nodes or services disappear.

   With a three-node cluster like you have configured, things will not be very resilient. Still, you can test what happens when the primary Master or a RegionServer disappears, by killing the processes and watching the logs.

1.2.5. Where to go next