Hands-On Exercise 10: prepare an OGC Web Processing Service¶

In this exercise we will prepare our workflow in order to expose an OGC Web Processing Service (WPS) [1] interface, and we will trigger it through a WPS Client.

Prerequisites¶

You have cloned the Hands-On git repository (see Clone the Hands-On repository),
(Only for python) You have installed the required software (see Prerequisites when using python).

Install the Hands-On¶

Install the Hands-On Exercise 10, just type:

cd
cd dcs-hands-on
mvn clean install -D hands.on=10 -P bash

Inspect the application.xml¶

Inspect the application.xml:

<?xml version="1.0" encoding="UTF-8"?>
<application id="beam_arithm">
  <jobTemplates>
    <!-- BEAM BandMaths operator job template  -->
    <jobTemplate id="expression">
      <streamingExecutable>/application/expression/run</streamingExecutable>
      <defaultParameters>           
        <parameter id="expression">l1_flags.INVALID?0:radiance_13>15?0:100+radiance_9-(radiance_8+(radiance_10-radiance_8)*27.524/72.570)</parameter>
        <parameter id="startdate" title="Start date" abstract="Start date of the TOI. Used as queryable for the MERIS Level 1 catalogue" scope="runtime" type="opensearch" target="time:start">2012-04-06T10:24:29.000Z</parameter>
        <parameter id="enddate" title="End date" abstract="End date of the TOI. Used as queryable for the MERIS Level 1 catalogue" scope="runtime" type="opensearch" target="time:end">2012-04-07</parameter>
        <parameter id="qbbox" title="Bounding Box" abstract="The bounding box parameter" scope="runtime" type="opensearch" target="geo:box">2.99,58.45,0.53,58.26</parameter>
      </defaultParameters>
    </jobTemplate>
    <!-- BEAM Level 3 processor job template  -->
    <jobTemplate id="binning">
      <streamingExecutable>/application/binning/run</streamingExecutable>
      <defaultParameters>           
        <parameter id="cellsize">9.28</parameter>
        <parameter id="bandname">out</parameter>
        <parameter id="bitmask">l1_flags.INVALID?0:radiance_13>15?0:100+radiance_9-(radiance_8+(radiance_10-radiance_8)*27.524/72.570)</parameter>
        <parameter id="bbox">-180,-90,180,90</parameter>
        <parameter id="algorithm">MIN_MAX</parameter>
        <parameter id="outputname">binned</parameter>
        <parameter id="resampling">binning</parameter>
        <parameter id="palette">#MCI_Palette
color0=0,0,0
color1=0,0,154
color2=54,99,250
color3=110,201,136
color4=166,245,8
color5=222,224,0
color6=234,136,0
color7=245,47,0
color8=255,255,255
numPoints=9
sample0=98.19878118960284
sample1=98.64947122314665
sample2=99.10016125669047
sample3=99.5508512902343
sample4=100.0015413237781
sample5=100.4522313573219
sample6=100.90292139086574
sample7=101.35361142440956
sample8=101.80430145795337</parameter>
        <parameter id="band">1</parameter>
        <parameter id="tailor">true</parameter>
      </defaultParameters>
      <defaultJobconf>
              <property id="ciop.job.max.tasks">1</property>
            </defaultJobconf>
    </jobTemplate>
  </jobTemplates>
    <workflow id="hands-on-10" title="Prepare an OGC Web Processing Service" abstract="Exercise 10, prepare an OGC Web Processing Service">           
    <workflowVersion>1.0</workflowVersion>
    <node id="node_expression">       
      <job id="expression"></job>     
      <sources>
        <source refid="cas:series">https://catalog.terradue.com/eo-samples/series/mer_rr__1p/description</source>
      </sources>
      <parameters>          
      </parameters>
    </node>
    <node id="node_binning">        
      <job id="binning"></job>      
      <sources>
        <source refid="wf:node">node_expression</source>        
      </sources>
      <parameters>
        <parameter id="bitmask"/>   
      </parameters>
    </node>
  </workflow>
</application>

Note the informational attributes for the WPS in the <workflow> tag:

    <workflow id="hands-on-10" title="Prepare an OGC Web Processing Service" abstract="Exercise 10, prepare an OGC Web Processing Service">           

Note the informational attributes in the <parameter> tags, to be exposed through the WPS. Also note the scope=”runtime” attribute:

    <jobTemplate id="expression">
      <streamingExecutable>/application/expression/run</streamingExecutable>
      <defaultParameters>           
        <parameter id="expression">l1_flags.INVALID?0:radiance_13>15?0:100+radiance_9-(radiance_8+(radiance_10-radiance_8)*27.524/72.570)</parameter>
        <parameter id="startdate" title="Start date" abstract="Start date of the TOI. Used as queryable for the MERIS Level 1 catalogue" scope="runtime" type="opensearch" target="time:start">2012-04-06T10:24:29.000Z</parameter>
        <parameter id="enddate" title="End date" abstract="End date of the TOI. Used as queryable for the MERIS Level 1 catalogue" scope="runtime" type="opensearch" target="time:end">2012-04-07</parameter>
        <parameter id="qbbox" title="Bounding Box" abstract="The bounding box parameter" scope="runtime" type="opensearch" target="geo:box">2.99,58.45,0.53,58.26</parameter>
      </defaultParameters>
    </jobTemplate>

Trigger the WPS service¶

Open a browser and type http://$HOSTNAME/dashboard
Click on the tab Invoke,
Click on the link Prepare an OGC Web Processing Service under Process List,
Type in the field Start date the value 2012-04-06T10:24:29.000Z,
Type in the field End date the value 2012-04-07,
Type in the field Bounding Box the value 2.99,58.45,0.53,58.26,
Click on the button Run Process,
Follow the execution until it ends (more or less five minutes).

The following images show the steps that we have just performed:

Recap¶

We prepared an application.xml suitable for the OGC WPS;
We triggered the service through the WPS Client included in the Sandbox Dashboard.

Footnotes

[1]	OGC Web Processing Service