Copyright © 2014 Open Geospatial Consortium.
39 This processing node implements the stage-in process with an emulation of the quality
control selection process defined by a CNR scientist. The input list of ASAR products produced by the OpenSearch query with date start, date stop and bounding box
parameters, retrieved from the ESA Catalogue available at
http:eo-virtual- archive4.esa.int
, is filtered according to quality control criteria, before their stage-in, discarding the useless products.
The second processing job as defined in the Application Descriptor file of the PaaS will be run as a set of tasks on a set of compute nodes monitored by the Hadoop framework. It
will start the processing of an ensemble of input SAR data as a selection of products, downloaded and ingested by the SBAS processor. Then intermediary results are passed to
the next processing step and so on.
5.3.4.3 Data processing service with OGC WPS-Hadoop
The PaaS service builds on technology designed for use cases having data-intensive requirements. CNR-IREA implemented the SBAS processing chain with full control of
code, parameters data flows, in a collaborative way within a shared Platform delivered as a Service a “Developer Cloud Sandbox, and using Cloud APIs to stage data and
deploy code on ad-hoc computing clusters.
Using Hadoop Streaming for applications integration, owners of processing algorithms are enabled to access distributed data holdings and to scale over computing clusters.
We present the main features of the PaaS in Figure 16 hereafter.
40
Copyright © 2014 Open Geospatial Consortium.
Oozie Project Tool Suite
Distributed Data Storage Distributed Data
Analytics
Virtualization Layer Science Application Development Layer
Platform Tools
Figure 16 - Developer Cloud Sandboxes service: data processing with OGC WPS-Hadoop
The service is operated via the OpenNebula technology for managing virtualized computing nodes, and uses standard Cloud APIs EC2, OCCI, JClouds for the Cloud
resources provisioning and Cloud Appliances deployment.
Client Applications interact with the processing layer via a simple OGC WPS interface, to trigger a processing, passing the selected processing parameters.
5.3.4.4 OGC-enabled Client application
A simple CSW OpenSearch and WPS client was integrated with the master node of the SBAS Cloud Appliance, so that users can configure a processing request over a selected
area and for a selected time span. It offers an invocation interface for the user cf. the “invoke” tab of the Cloud Appliance Dashboard in Figure 17 below.
