VOMegaPlot Server-The VOTable plotting utility (Version 1.0 Beta) |
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Introduction
VOMegaPlot Client-Server has been developed for plotting different
astronomical graphs using data stored in VOTable
format.
VOMegaPlot Server is hosting end of the VOMegaPlot Client-Server which handles the requests made by
VOMegaPlot Clients. When the Client sends the
plotting request, plotting of datasets happens at the server end, while only
the plotted image is transferred back to client. The basic concept can be shown as:
About VOMegaPlot Server
VOMegaPlot Client-Server has been developed as a part of the Virtual Observatory - India initiative by Persistent Systems and the Inter-University Centre for Astronomy and Astrophysics (IUCAA), in collaboration with Centre de Données astronomiques de Strasbourg (CDS).
Third Party Tools
- Ptplot 5.2, a 2D data plotter
and histogram tool implemented in Java. Ptplot
has been developed at EECS department at the
- VOPlot makes use of cds.astro
(Astronomical coordinate manipulation) package for projection maps. The
package has been developed by CDS,
- Log4j-1.2.4:-Log4j is a fast and flexible framework for logging application debugging messages.
Getting Started
VOMegaPlot Server has been optimized to handle multiple plot requests from different clients concurrently.
VOTable xml files needs to be parsed before it is loaded with VOMegaPlot Server.
Launching VOMegaPlot Server:
VOMegaPlot Server can be launched using following commands:
-If the VOMegaPlot Server is launched using
RMI:
java -Djava.rmi.server.hostname=<hostname> -jar <VOMegaPlot-Server jar file> [-requesthandlers
<number of request handlers] [-rmiport <rmi port number>]
[-port <port number> ]
[-path <file path>]
where,
requesthandlers is the number of handlers that manage client request., the
default value is 2.
Note: It is advisable to use VM argument -Xmx
to increase the java heap size depending upon the number of
request handlers.
rmiport
is RMI registry port number on the server, the default value is 1099
port is the port number on which the remote object receives
calls, the default value is 2020
path is the filepath where voi files are stored, the default value is the current directory .
(voi files are generated by parsing VOTable files. The method to parse VOTable files is explained under the parse section)
java.rmi.server.hostname The value of this property represents the host name
string that should be associated with remote stubs for locally created remote
objects, in order to allow clients to invoke methods on the remote object. In 1.1.7
and later, the default value of this property is the IP address of the local
host, in "dotted-quad" format.
Example: java –Djava.rmi.server.hostname=vom.iucaa.ernet.in
-jar VOMegaPlot_Server.jar -requesthandlers
5 –Xmx512 -rmiport
2000
-port 80 -path g:\sample-files\
-If the VOMegaPlot
Server is launched using Sockets:
java -jar <VOMegaPlot-Server
jar file> [-requesthandlers <number of request
handlers] [-port <port number> ]
[-path <file path>] -usesockets
where,
requesthandlers is the number of handlers that manage client request., the
default value is 2
port is the
port number on which server socket is created, the default value is 2020
path is the filepath where voi files are stored, the default value is the current
directory .
usesockets is used to launch the Server using sockets.
(voi files are generated by parsing VOTable files. The method to parse VOTable files is explained under the parse section)
Also,
[] indicates that the argument is optional.
Example: java -jar VOMegaPlot_Server.jar -requesthandlers
5 -port 80 -path g:\sample-files\ -usesockets
Note: Please note that, by default VOMegaPlot Server launches using RMI method, to launch it using sockets use the parameter –usesockets.
Parsing VOTable file:
java -jar
VOMegaPlot_Server.jar -parse <path of xml> [-targetdir <path to the
output directory>]
The parsing operation creates a set of intermediate files in
the directory specified by targetdir. The intermediate files will be created in the
working directory in case if targetdir is not
specified. The parsing operation creates two files with extension as ‘cfo’ for each numerical column. It also creates a file with
extension as ‘voi’ which should be subsequently used
for loading with VOMegaPlot. All these files will
have their names beginning with the name of the xml file. These files should be
placed together and the file with ‘voi’ as extension
should be used for loading instead of the VOTable xml file.
Please note that, the parsing operation need to be performed only once for a given VOTable xml file. User can reuse the set of intermediate files, created as result of the parsing, any number of times for plotting. Also note that parsing time depends on the number of columns and number of rows that are present in the VOTable file. For a catalog which has about 50 columns and 1,000,000 rows per column, it takes about 4 hours on a machine having Pentium 4 (2.66 GHz) processor and 512M memory on the Windows platform.
Setting RADEC values:
After parsing, a voi file can also be preset with its RADEC values. Use the following command to perform this operation.
java -jar <VOMegaPlot_Server
jar file> -setRADEC <filename>.voi
Note: To run VOMegaPlot Server, you must have JRE 1.4.2 or higher installed. To see the version of JRE installed, type the following command at the command prompt:
java -version
Server log files
The log messages are logged in logs/VOMCSLog.txt file. In this file, the application logs the messages with a client id which is unique to each client.
The log message is in the following sequence:
1. Priority level of the log message
2. Logging event category
3. client-id :< message text>
Feedback Address
We would be happy to receive any feedback/comments on VOMegaPlot Client-Server. For feedback and comments please contact voindia@vo.iucaa.ernet.in.