From Brown University Robotics
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Revision as of 21:19, 5 May 2010
The HBase Server
To Start Hbase on maria
If you need to restart Hbase on maria, follow these instructions. Currently Hbase is installed in bkorel's home directory. The start scripts are have global read and execute permissions, so anyone should be able to restart Hbase.
Start the Hbase server with the below command. You will be prompted twice for your password to localhost.
Start the thrift server:
bin/hbase-daemon.sh start thrift --port=9091
If you do not specify the port via the command line, the thrift server will use the default port of 9090. However if you get the error "Could not create ServerSocket on address /192.168.0.1:9090" when starting the thrift server, you need to specify a different port number as in the above command. Note: if the thrift server is started using a different port, 9091 is currently hard coded in the Hbase ros node (bin/record) and should be changed.
To start the Hbase shell:
Example Hbase shell usage:
hbase> # Type "help" to see shell help screen hbase> help hbase> # To create a table named "mylittletable" with a column family of "mylittlecolumnfamily", type hbase> create "mylittletable", "mylittlecolumnfamily" hbase> # To see the schema for you just created "mylittletable" table and its single "mylittlecolumnfamily", type hbase> describe "mylittletable" hbase> # To add a row whose id is "myrow", to the column "mylittlecolumnfamily:x" with a value of 'v', do hbase> put "mylittletable", "myrow", "mylittlecolumnfamily:x", "v" hbase> # To get the cell just added, do hbase> get "mylittletable", "myrow"
In case the logging table is deleted or inaccessible, run the following command to create the appropriate table and column families for storing data using the Hbase ros node:
hbase> create "session_table", "timestamp", "msg", "topic"
To Stop Hbase
Hbase needs to be properly shut down; currently there are problems accessing previously stored data otherwise. Run the following two commands to stop the thrift and Hbase servers:
bin/hbase-daemon.sh stop thrift bin/stop-hbase.sh
Instructions to Install Hbase on maria
Note: root permissions are required.
Hbase is currently run in standalone, non-distributed mode.
ZooKeeper is a high-performance coordination service for distributed applications. HBase depends on ZooKeeper, since HBase keeps the location of its root table, who the current master is, and what regions are currently participating in the cluster in ZooKeeper. By default HBase manages a single ZooKeeper instance for you. In standalone and pseudo-distributed modes this is usually enough, but for fully-distributed mode you should configure a ZooKeeper quorum.
Download and unpack a stable release: ZooKeeper. Currently 3.2.2 is installed.
bkorel: determine if writing a conf file is necessary for standalone mode.
If you run into problems, follow ZooKeeper Getting Started.
Hadoop is a distributed computing platform. If running in standalone mode, you will not need to install/configure Hadoop becuase HBase by default uses the local filesystem. Distributed modes require an instance of the Hadoop Distributed File System (DFS). See the Hadoop requirements and instructions for how to set up a DFS.
Download Hadoop from
ip hard coded in ThriftServer.java
Logging in HBase
If logging data for the first time, add the following line to your .bashrc file:
Otherwise you will get the following error when running the Hbase ros node: "ImportError: No module named thrift"
Logging ROS messages in HBase is very easy. Check out the hbase ros node currently in the experimental section of brown-ros-pkg. In the bin directory is a script called record which takes two or more arguments. The first id is a session-id which is simply a string used to retrieve your session later. The session-id must be unique, if not you will be prompted to enter a new session-id. The subsequent arguments are the names of the topics you wish to record. It searches for the exact topic, so be careful with capitalization and remember all topic names start with /. When you're finished recording simply hit Ctrl-C, and your data is logged in the repository. Currently there can be issues with data loss if the server is shut down improperly, so be careful.
The following command logs the four topics /headF /cmd_Larm /cmd_Rarm /blobs under the session-id 3simplex1
./record 3simplex1 /headF /cmd_Larm /cmd_Rarm /blobs
Retrieving Data from HBase
Browsing the Table
Retrieving and Filtering Data