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Concept - Process Chains (valid to 11.1)

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 (valid to 11.1)

Technical Overview

XSD can be found in shared/system/config/cluster/processchain.xsd
processchain.xml.example shows all important elements and attributes
Build medium sized process chains – incl. dependencies, to restart a group
Build chains in chains to reduce schedule effort – 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.INSTANCE.SHARE>/system/config/cluster.

Info

The default installation includes an example file, processchain.xml.example.

The main configurable elements include:

<chain>
The root element of the process chain XML file. Important attributes include name (used in the System Management, module 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 the System Management module 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 the System Management module 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) 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

Execution Plan 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

<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 either represented by a "bit"-status or a text for each status. In the following you can see the mapping of bit and text status.

Error Mapping

STATUS_SUCCESS     = 0;
STATUS_WARNING     = 1;
STATUS_FAILURE     = 2;
STATUS_ERROR       = 4;
STATUS_NOTFOUND    = 8;
STATUS_INTERRUPTED = 16;

ProcessConstants registers text and bit mapping.

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 GANT diagram showing the execution sequence and more.

You may access an alternative view via Scheduling | Schedules | Last Run date of your process chain.

Disclaimer

The information provided in the Knowledge Base may not be applicable to all systems and situations. Intershop Communications will not be liable to any party for any direct or indirect damages resulting from the use of the Customer Support section of the Intershop Corporate Web site, including, without limitation, any lost profits, business interruption, loss of programs or other data on your information handling system.

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