From Brown University Robotics
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Revision as of 20:09, 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 command below. You will be prompted for your password to localhost twice.
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"
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 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