Introduction

This concept is aimed at developers and describes the organization of tasks in process chains. In Intershop Commerce Management, process chains help to automate the sequential execution of interdependent scheduled jobs or pipelines.

As a developer or administrator, you can easily configure process chains using XML files.

By using process chains, you can:

• Avoid conflicts with overlapping jobs
• Shorten waiting periods between jobs
• Minimize the scheduling effort
• Restart a set of schedules if a task or schedule fails
• Send notifications when a schedule or a set of schedules fails or finishes successfully

References

• Cookbook - Process Chains

Technical Overview

• The XSD can be found as processchain.xsd in our XML schema definition at GitHub.
• For an overview of all important elements and attributes, refer to example-processchain.xml at GitHub.
• Build medium sized process chains – incl. dependencies, to restart a group
• Build chains in chains to reduce scheduling overhead – call a process chain schedule

Types of Elements

An umbrella element defines how the tasks inside the element will be executed. An umbrella element is logged as a process. This allows the administrator to easily see the impact of the group.

• Task List: For executing multiple tasks
  • Sequence - Executes all tasks one after another
  • Concurrent - Executes all tasks in parallel
• Task Types:
  • Job - Executes a configuration, concurrent=true declares if the execution is sequential or parallel.
  • Pipeline - Executes a pipeline
• Error: All tasks are executed in sequence if an error occurs in the outer task list.

Example of a Process Chain

The error sequence is executed if "Step 2.2.1 Job" or "Step 2.2.2 Pipeline" fails. For more details on fine-tuning error handling, refer to the description of the <ignore> element in the next section.

Process Chain Elements

Administrators can define process chains using XML files to be located in $IS_SITES.

The main configurable elements include:

• <chain>
  The root element of the process chain XML file. Important attributes are name (used in Intershop System Management | Monitoring | Locking | Processes), defaultChainElementTimeout (default 60) which defines the default timeout in minutes for all child elements (concurrent, sequence, job, pipeline), and keepAliveTime which defines the time that threads exceeding the core pool size may remain idle before being terminated.

• <concurrent>
  Child element of <chain> or <sequence>. Includes jobs or pipelines to be executed in parallel. The attribute name is used in Intershop System Management | Monitoring | Locking | Processes. Can define a timeout in minutes, falling back to the defaultChainElementTimeout if it is undefined or set to zero.

• <sequence>
  Child element of <chain> or <concurrent>. Includes jobs or pipelines to be executed sequentially in the given order. The attribute name is used in Intershop System Management | Monitoring | Locking | Processes. Can define a timeout in minutes, falling back to the defaultChainElementTimeout if it is undefined or set to zero.

• <job>
  Child element of <sequence> or <concurrent>. Specifies a job to be executed within the chain. The next table lists the attributes for<job>.

  The following attributes can be assigned to the <job> element:

  Attribute	Description
  job	Specifies the name of the job as defined in the Intershop System Management Schedules module (mandatory).
  name	Specifies a display name for this job to be used in the Intershop System Management | Monitoring | Locking | Processes module.
  domain	Can define a specific domain for the job execution (optional). By default, the chain element job is executed in the domain of the process chain.
  allsites	Can specify whether the job executes in all domains (true|false), default is false.
  concurrent	With allsites=true, can specify whether the job executes in parallel in all domains (true|false), default is false.
  timeout	Can define a timeout in minutes, falling back to the defaultChainElementTimeout if it is undefined or set to zero.

• <pipeline>
  Child element of <sequence> or <concurrent>. Specifies a pipeline to be executed within the chain. The next table lists the attributes for<pipeline>.

  The following attributes can be assigned to the <pipeline> element:

  Attribute	Description
  pipeline	Specifies the name of the pipeline to be executed.
  name	Specifies a display name for this pipeline to be used in the Intershop System Management Monitoring | Locking | Processes module.
  domain	Can define a specific domain for the pipeline execution (optional). By default, the chain element pipeline is executed in the domain of the process chain.
  startnode	Can define a specific pipeline start node (optional), default is Start.
  login	Can define the login name that the pipeline to be executed may require.
  password	Can define the password if the pipeline to be executed requires a specific login.
  timeout	Can define a timeout in minutes, falling back to the defaultChainElementTimeout if it is undefined or set to zero.

• <error>
  Optional child element of <sequence>. Specifies a dedicated <job> or <pipeline> that is to be executed in case the preceding jobs or pipelines within the <sequence> have failed.

  Note

  Make sure that <error> is the last element within the corresponding <sequence>.

• <parameter>
  Optional child element of <pipeline>. Can specify the parameter that the pipeline to be executed may require.

• <description>
  Optional child element of <sequence>, <concurrent>, <job>, or <pipeline>. Specifies a description to be displayed in the Intershop System Management Monitoring | Locking | Processes module.

• <ignore>
  Optional child element of <sequence>, <concurrent>, <job>, or <pipeline>. Can specify status codes (SUCCESS | WARNING | FAILURE | ERROR | NOTFOUND | INTERRUPTED | STUCK) returned by the corresponding chain element on execution that should be ignored for the rest of the process chain execution. This allows the process chain execution to continue even if an error occurs in one of its sub-tasks.

XML Example

<?xml version="1.0" encoding="UTF-8"?>
<p:chain name="Chain Example">
    <p:sequence name="Chain is a sequence">
        <p:job job="CheckOrders" name="Step 1 - Job" />
        <p:concurrent name="Step 2 - Concurrent">
            <p:pipeline pipeline="ExecuteProcessChain" name="Step 2.1 - Pipeline">
                <p:parameter name="XmlFileName">*.xml</p:parameter>
            </p:pipeline>
            <p:sequence name="Step 2.2 - Sequence" timeout="30">
                <p:description>Sequence example which runs into timeout after 30 minutes if not completed</p:description>
                <p:job allsites="true" concurrent="true" job="ArchiveOrders" name="Step 2.2.1 - Job" />
                <p:pipeline pipeline="..." name="Step 2.2.2 - Pipeline" />
                <p:error name="Step 2.2 Error Sequence">
                    <p:pipeline pipeline="SendNotification" name="Error - Pipeline" />
                </p:error>
            </p:sequence>
        </p:concurrent>
    </p:sequence>
</p:chain>

Ignore - Sub Element of Each Task

The ignore element can suppress errors of a task or an umbrella element. The error element will ignore the declared states, in case they occur in the tasks of the same level.

<p:concurrent name="Step 2 - Concurrent">
    <p:sequence name="Step 2.2 - Sequence">
        <p:ignore>NOTFOUND</p:ignore>
        <p:job allsites="true" concurrent="true" job="ArchiveOrders" 
                   name="Step 2.2.1 - Job" />
        <p:pipeline pipeline="..." name="Step 2.2.2 - Pipeline" />
        <p:error name="Step 2.2 Error Sequence">
            <p:pipeline pipeline="SendNotification" name="Error - Pipeline" />
        </p:error>
    </p:sequence>
</p:concurrent>

Status Mapping

Each task execution has a result that is indicated by a status. This status is represented by a "bit"-status as an enum value (ProcessChainStatus) for each status. Parent processes can do a bitwise OR to combine the status of their children.

Process Chain View

To get an overview of the execution of a process chain:

In Intershop System Management, switch to Monitoring | Locking | Processes | <your subprocess>.
Here you can find information on acquired resources, the chain elements, the execution time, the status of your process chain, a GANTT diagram showing the execution sequence and more.