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Welcome to the 11th screencast on Grid computing brought to you by the Direct User Support
Team operating in the context of the EGEE-III Project. During this screencast we will discuss
the features of the AMGA tool.
AMGA stands for Arda Metadata Catalogue Project and it is a service that allows grid users
to store various metadata relating to their data files. The AMGA metadata catalog may
be accessed either via the mdclient command line utility or via a set of API calls. During
this screencast we will focus on the usage and configuration of the mdclient AMGA metadata
client and how to create simple metadata structures inside an AMGA server.
In order to use the AMGA service the amga-cli package needs to be installed on our User
Interface. One then needs to edit the configuration file .mdclient.config which should reside
in the user's home directory. As you can see I will be using the seegrid AMGA service for
this demonstration.
Before using the service I need to create a short term proxy using the voms-proxy-init
command.
To demonstrate the usage of the AMGA service I have created a small dataset of files residing
on Grid Storage Elements. On the LFC service these are stored under the /grid/seegrid/demo
folder. Using the lfc-ls command I may browse the contents of this directory. As you can
see for the needs of the demonstration the dataset is comprised of just only a few files.
I now connect to the AMGA service with the mdclient command with the goal to add metadata
to my data files.
On the AMGA service metadata is stored in a directory structure. Using the dir or ls
commands I may view the contents of the current working directory. I enter the /grid/seegrid
directory and create a new directory named demo thus emulating the LFC structure discussed
earlier.
I may now add attributes to the files residing to this directory using the addattr command.
For the needs of the demonstration I am adding an ID of type integer, a Size of type integer
and a Storage_Element of type varchar.
I may
now add entries to this folder using the addentry command.
In order to query my files and select the ones matching each time the criteria set I
may now use the selectattr function. In this first example I select the files with Size
larger than 10KB. In the second example I only select the files residing on the se.ipb.ac.rs
Storage Element.
To delete entries from the AMGA service I now use the rm command. Finally to delete
the directory demo holding the metadata I may use the rmdir command once it is empty.
Finally, to get a list of help topics associated with the AMGA service one may use the help
command.
This concludes our screencast on the AMGA metadata service. On behalf of the Direct
User Support Team thank you for watching.