SMILA/Documentation/BPEL Workflow Processor

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Basic Configuration

The BPEL WorkflowProcessor expects its configuration in subdirectory "org.eclipse.eilf.processing.bpel" of the configuration directory. See the test bundle "org.eclipse.eilf.processing.bpel.test" for an example. In this it expects a file named processor.properties that describes the main configuration. It can contain the following SMILA specific properties:

  • pipeline.dir (default="pipelines"): The subdirectory of this directory that contains the BPEL process files (together with all needed XSD and WSDL files) and the ODE specific deploy.xml file. See below for details.
  • pipeline.timeout (default="300"): Maximum time in seconds allowed for processing a pipeline. If a pipeline invocation takes longer, it is aborted with an error. If you expect that longer evaluations are possible in your application (e.g. analysing very large documents) you may want to increase this value.
  • record.filter (default = none): A record filter defining the attributes and annotations that should be contained in BPEL workflow objects. Of none is set, the workflow objects will contain only the record IDs to be processed. You should take care to add only those attributes and annotations to the filter that are actually used in any pipeline, for adding too many (and too huge) elements to the workflow object may decrease performance and uses more memory. As the WorkflowProcessor uses the Blackboard to filter objects, you must define the filters in "org.eclipse.eilf.blackboard/RecordFilters.xml".

As the BPEL WorkflowProcessor is based on the Apache ODE BPEL engine [1], you can also add all ODE specific configuration properties to this file, just use the prefix "ode." See ODE documentation for details. You have to add at least the configuration for a database connection which ODE needs for internal purposes (e.g. storing process definitions). For SMILA purposes usually a in-memory HSQLDB instance is completely sufficient, the HSQLDB library is incldued in bundle "org.apache.ode". Define it using the following properties:

ode.db.mode=internal
ode.db.int.driver=org.hsqldb.jdbcDriver
ode.db.int.jdbcurl=jdbc:hsqldb:mem:odedb
ode.db.int.username=sa
ode.db.int.password=

If you want to use a "real" database you will have to make the JDBC driver available to bundle "org.apache.ode", and check the ODE documentation for how to prepare the database schema for ODE.

Pipeline definition using BPEL

The minimal BPEL process for SMILA pipelines looks like this:

<?xml version="1.0" encoding="utf-8" ?>
<process name="$PIPELINENAME" targetNamespace="http://www.eclipse.org/eilf/processor"
    xmlns="http://docs.oasis-open.org/wsbpel/2.0/process/executable" xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:proc="http://www.eclipse.org/eilf/processor" expressionLanguage="urn:oasis:names:tc:wsbpel:2.0:sublang:xpath1.0"
    xmlns:rec="http://www.eclipse.org/eilf/record" xmlns:id="http://www.eclipse.org/eilf/id">
 
    <import location="processor.wsdl" namespace="http://www.eclipse.org/eilf/processor"
        importType="http://schemas.xmlsoap.org/wsdl/" />
 
    <partnerLinks>
        <partnerLink name="Pipeline" partnerLinkType="proc:ProcessorPartnerLinkType" myRole="service" />
    </partnerLinks>
 
    <extensions>
        <extension namespace="http://www.eclipse.org/eilf/processor" mustUnderstand="no" />
    </extensions>
 
    <variables>
        <variable name="request" messageType="proc:ProcessorMessage" />
    </variables>
 
    <sequence>
        <receive name="start" partnerLink="Pipeline" portType="proc:ProcessorPortType" operation="process"
            variable="request" createInstance="yes" />
 
        <reply name="end" partnerLink="Pipeline" portType="proc:ProcessorPortType" operation="process" variable="request" />
        <exit />
    </sequence>
</process>

To create a new pipeline copy this to a new file with suffix ".bpel" in the configuration directory "org.eclipse.eilf.processing.bpel/pipelines" and replace $PIPELINENAME with the desired name of your pipeline. Add the files from the "xml" directory in bundle org.eclipse.eilf.processing.bpel (id.xsd, record.xsd and processor.wsdl). Then create a file "deploy.xml" in the same directory like this and replace $PIPELINENAME by the name of your pipeline:

<deploy xmlns="http://www.apache.org/ode/schemas/dd/2007/03" xmlns:proc="http://www.eclipse.org/eilf/processor">
    <process name="proc:$PIPELINENAME">
        <in-memory>true</in-memory>
        <provide partnerLink="Pipeline">
            <service name="proc:$PIPELINENAME" port="ProcessorPort" />
        </provide>
    </process>
</deploy>

You can now add service or pipelet invocations to your pipeline BPEL. To add another pipelet you have to add only another BPEL file and copy the <process> element in deploy.xml for the new pipeline.

Pipelet invocations

Pipelets (aka "Simple Pipelets") are classes that implement interface "org.eclipse.eilf.processing.SimplePipelet" (in bundle "org.eclipse.eilf.processing") and are listed in the "EILF-Pipelets" manifest header of the bundles that contain them. They are configured by the WorkflowProcessor on pipeline initialization. One instance is created for each time they occur in any pipeline, instances are not shared between multiple pipelines. Examples that come with the base SMILA distribution are

  • in bundle org.eclipse.eilf.processing.pipelets:
    • org.eclipse.eilf.processing.pipelets.SetAnnotationPipelet: Sets a configured annotation for each record in the input variable.
    • org.eclipse.eilf.processing.pipelets.CommitRecordsPipelet: Commits each record in the input variable on the blackboard to the storages.
    • org.eclipse.eilf.processing.pipelets.HtmlToTextPipelet: Extract plain text and metadata from an HTML document in an attribute or attachment of each record and writes it to configurable attributes or attachments.
  • in bundle org.eclipse.eilf.processing.pipelets.aperture:
    • org.eclipse.eilf.processing.pipelets.aperture.AperturePipelet: Uses Aperture to convert many kinds of documents to plain text.
  • in bundle org.eclipse.eilf.processing.pipelets.xmlprocessing:
    • A collection of pipelets for XML processing (XSLT, XPath selection, ...) of documents.

To use such a pipelet in your pipeline use the SMILA specific BPEL extension activity "invokePipelet" somewhere between <receive> and <reply> in your BPEL process:

<extensionActivity name="invokeSomePipelet">
  <proc:invokePipelet>
    <proc:pipelet class="org.eclipse.eilf.pipelet.SomePipelet" />
    <proc:variables input="request" output="request" />
    <proc:PipeletConfiguration>
    <proc:Property name="configuration-property-name">
      <proc:Value>configuration-property-value"/>
    </proc:Property>
    <!-- more configuration properties -->
    </proc:PipeletConfiguration>
  </proc:invokePipelet>
</extensionActivity>

Replace the class name with the class name of the pipelet to use and add configuration properties as needed - this should be documented by the pipelet provider. If the output variable is the same as the input variable (which is usually sufficient), you can omit the "output" attribute.

Service invocations

Services (aka "Processing Services") are classes that implement interface "org.eclipse.eilf.processing.ProcessingService" (in bundle "org.eclipse.eilf.processing") and registered as OSGi services for this interface with a service property named "eilf.processing.service.name" descrining the name of this service. They are initialised and configured independently of the workflow engine and invocations from different pipelines will use the same instance. An example in the base SMILA distribution is the "LuceneService" in bundle "org.eclipse.eilf.lucene" for adding records to a Lucene index.

To use such a service in your pipeline use the SMILA specific BPEL extension activity "invokeService" somewhere between <receive> and <reply> in your BPEL process:

<extensionActivity name="invokeLuceneService">
  <proc:invokeService>
    <proc:service name="LuceneService" />
    <proc:variables input="request" />
  </proc:invokeService>
</extensionActivity>

The output attributes of <proc:variables> is supported here in the same way as in <invokePipelet> (see above), but is omitted in this example because the result of the service invocation should be written to the input variable again. There is no further configuration content in this service invocation. Consult the service documentation about how to configure it.

Setting annotations in Service and Pipelet invocations

Both kinds of invocations support setting annotations on the records to process inline in the extension activity XML. This is more important for invocation of services because the operation of some services is controlled by service-defined root annotations of the processed records, but nevertheless it works for invocation of pipelets in the same way. To use this just add a <proc:setAnnotations> element to <proc:invokeService> or <proc:invokePipelet> that contains the annotations in the standard annotation XML format defined in [Data Model and XML representation]. E.g., the LuceneIndexService (Bundle org.eclipse.eilf.lucene) uses a annotation to define the index to be changed and the type of change (ADD, DELETE). In the example pipeline "addpipeline.bpel" of EILF.application this looks like this:

<extensionActivity name="invokeLuceneService">
  <proc:invokeService>
    <proc:service name="LuceneIndexService" />
    <proc:variables input="request" output="request" />
    <proc:setAnnotations>
      <rec:An n="org.eclipse.eilf.lucene.LuceneIndexService">
        <rec:V n="indexName">test_index</rec:V>
        <rec:V n="executionMode">ADD</rec:V>
      </rec:An>
    </proc:setAnnotations>
  </proc:invokeService>
</extensionActivity>

This sets an annotation named "org.eclipse.eilf.lucene.LuceneIndexService" with two named values "indexName=test_index" and "executionMode=ADD" to all records in the "request" variable. All existing annotations of the same name are removed before the new annotations are set.


Pipeline invocations

You can also invoke one pipeline from another to group service or pipelet invocations that belong together. To do this you have to use the standard BPEL invoke activity to invoke a BPEL partner link for the sub pipeline:

  • define a partner link in the <partnerLinks> section of the BPEL file, replace $SUBPIPELINENAME with the name of pipeline to invoke as defined in its <process> element:
<partnerLinks>
  <partnerLink name="Pipeline" partnerLinkType="proc:ProcessorPartnerLinkType" myRole="service" />
  <partnerLink name="$SUBPIPELINENAME" partnerLinkType="proc:ProcessorPartnerLinkType" partnerRole="service" />
</partnerLinks>
  • add a invoke activity between <receive> and <reply>, replace $SUBPIPELINENAME with the pipeline name and adapt the inputVariable and outputVariable attributes if necessary (omitting "outputVariable" is not allowed here!):
<invoke name="invokeSubPipeline" operation="process" portType="proc:ProcessorPortType" 
  partnerLink="$SUBPIPELINENAME" inputVariable="request" outputVariable="request"
/>
  • add a declaration for the partner link in the deploy.xml entry of your pipeline:
<deploy xmlns="http://www.apache.org/ode/schemas/dd/2007/03" xmlns:proc="http://www.eclipse.org/eilf/processor">
    <process name="proc:$PIPELINENAME">
        <in-memory>true</in-memory>
        <provide partnerLink="Pipeline">
            <service name="proc:$PIPELINENAME" port="ProcessorPort" />
        </provide>
        <invoke partnerLink="$SUBPIPELINENAME">
            <service name="proc:$SUBPIPELINENAME" port="ProcessorPort" />
        </invoke>
    </process>
</deploy>

Advanced Process definition

You can of course use all other BPEL elements, too, to create your pipelines like conditions, iterations, parallel flows, invocation of external Web Services, etc. However, to describe them is beyond the scope of this introduction and requires "real" knowledge about BPEL (and WSDL, for invoking Web Services).