Information Technology Reference
In-Depth Information
produced within the GP-SCL-EXECUTION task is transferred from the DCI to
the machine running the science gateway for this purpose.
GP-SCL-ANIMATION produces animation (movie) of a dilute,
trapped
Bose
Einstein condensate evolution in time. This part of the workflow is CPU
intensive and is executed on the DCI.
-
GP-SCL-PUBLICATION accumulates results, technical metadata, graphs, and
locations of the movies, and stores them in the document-oriented database.
gurations
and numerical results from all applications supported by the science gateway.
Initially, it was deployed using a relational database, but with the increase of the
number of physical properties to be monitored, it has become very dif
AEGIS CMPC DB is a document-oriented database that stores con
cult to break-
out the design of the SG into relational schemas. Instead of perpetual reorganization
of schemas, the database back-end has been migrated to the document-oriented data
model. Due to several additional features, such as offline replication, multiversion
concurrency control, incremental replication, and fault-tolerance, MySQL tech-
nology (Harrison 2008) has been replaced by CouchDB technology (Anderson
2009).
Querying of and structuring the information available in the science gateway is
realized by CouchDB views. Different views are constructed by functions that act as
a mapping part of the map/reduce operation. These functions take the documents
and transform them into single values that they return. CouchDB indexes the view
and keep the indexes updated as new documents are added, removed, or updated.
Authentication and authorization of the requests coming to the AEGIS CMPC
SG, together with the tracking and merging mechanisms, are implemented as an
additional layer placed in front of the CouchDB. In order to change or add new
information (POST and PUT methods), a workflow developer has to be authenti-
cated and authorized; however, reading of information is publicly available (GET
method). Authentication and authorization could be done by username/password,
an X.509 certi
cate; this is
followed by an update of the document with the JSON tracking structure. This
section contains workflow developer information, the IP address of the client from
which the request was triggered, and the timestamp of the action. For this reason,
each document stored in AEGIS CMPC CouchDB has additional JSON structure
related to the tracking mechanism.
All documents stored in CouchDB are versioned, and CouchDB determines
which of the changes will be stored as the latest revision. When doing this, it does
not attempt to merge the conflicting revision. A developer always decides how the
merging should be done, and it is up to a developer to specify the latest revision.
This task is simpli
cate, or an X.509 RFC 3,820-compliant proxy certi
ed with the AEGIS CMPC CouchDB merging mechanism, and
a workflow developer no longer needs to deal with the CouchDB revisions. The
system automatically discovers the latest version of a particular document, and
performs merging of the existing information with additional information. Existing
CouchDB documents could be updated with different or new information only,
which is not the case in the standard CouchDB model. In addition, the AEGIS
Search WWH ::
Custom Search