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The Join Job (JobSchedulerJoinOrders) is used to join up two parallel executing child segments in a Job Chain. It then continues processing in a single thread once processing of the parallel threads has been completed. It is used in two Job Chain Patterns - split Split and joinJoin and "Y".

The Join Job can only be used within a Job Chain and is only available for JobScheduler versions 1.11.4 and newer, See the How To Synchronize Job Execution Across Job Chains article for information about synchronizing Jobs in different Job Chains and for joining up parallel executing child Job Chain segments in JobScheduler versions 1.11.3 and older.

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Join Patterns

split and join Pattern

The configuration of the Join Job for the split the Split and joinJoin pattern is described in the How to Execute Jobs in a Job Chain in Parallel article.

Relevant for the current article is that while in the Join job is used with the Split Job without any parameters being configured, the Split Job: Split and Join pattern, the Split Job generates the configuration information required by the Join job. This information must be configured separately for the "Y" pattern. The information generated by the the Split Job is:

• generates a parameter - required_orders - which is forwarded to the Join Job. This parameter defines the number of orders that the Join Job has to receive before processing the main Job Chain continues with processing of the Join Job itself
• generates an Order for each of the child Job Chain segments that is to be processed in parallel. The end state of each of these Orders is the state of the Join Job.the

The ID set for each of the child Job Chain segment Orders is made up from the ID of the main Order and state in the Job Chain of the first Job in the child Job Chain segment.

'Y' Pattern

The following diagram shows the "Y"-pattern Job Chain used in the example download archive that is linked from this article. Note that some of the elements in this pattern have been given particular functions to provide a working example of the Join Job and are not required for its operation in "normal" use.

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Solution

• Download the example y_join.zip
• Extract the archive to a folder ./config/live of your JobScheduler Master installation.
• The archive will extract the files to a folder y_join. 
• The y_join folder can be renamed if required, the solution does not require the use of specific folder or Job names.

Implementation

The join Job has basically a counting function. This makes it significantly faster than the sync Job which checks the IDs of the jobs being processed.

Note that some of the elements in this example have been given particular functions to demonstrate the functioning of the Join Job and are not required for its operation in "normal" use.

An Order (in this example main_order) is started with a parameter (required_orders). This parameter is read by the join Job, which will then wait until the number of Orders specified in the parameter (here it is 12) that have the state of the join Job as their end state have been processed.

• to wait until a

The Job Chain, Jobs and Orders

The two "Y" branches in this example and are shown in the pattern diagram above each have . Each branch has a different purpose:

• The left branch is used by an Order (main_order) that proceeds over the Join Job and Job B to the end of the Job Chain (state: success).
• The right hand branch is used by an Order (main_order_add-order) that starts at Job A and ends at the Join Job.

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<?xml version="1.0" encoding="ISO-8859-1"?>
<job_chain  title="Y Join">
    <job_chain_node  state="100" job="generate_orders" next_state="wait" error_state="error"/>
    <job_chain_node  state="150" job="job_a" next_state="join" error_state="error" delay="10"/>
    <job_chain_node  state="wait" job="wait" next_state="join" error_state="error"/>
    <job_chain_node  state="join" job="join" next_state="200" error_state="error"/>
    <job_chain_node  state="200" job="job_b" next_state="success" error_state="error"/>
    <job_chain_node  state="success"/>
    <job_chain_node  state="error"/>
</job_chain>

The demonstration isgenerate_orders job contains the following script:

<?xml version="1.0" encoding="ISO-8859-1"?>


<job  order="yes" stop_on_error="no">
    <script  language="java:javascript">
        <![CDATA[
function spooler_process(){

    // merge parameters from task and order
    var params = spooler_task.params;
    params.merge( spooler_task.order.params );
 
    // set variable
    var generate_orders = params.value( 'generate_orders' );
    var jobChain = spooler.job_chain('/test/join/y_join/y_join');

    // log parameter
    spooler_log.info( 'generate_orders = ' + generate_orders);
 
    // generate orders
    for (i=0;i<generate_orders;i++){
       var order = spooler.create_order();
       order.id = spooler_task.order.id + "_" + i;
       order.params.merge(spooler_task.order.params);
       order.end_state="join";
       order.state="150";
       jobChain.add_order(order);
    }

    return true;
}
        ]]>
    </script>

    <run_time />
</job>

The test Order starts the first Job (job_create_orders) in the job_chain_test Job Chain:

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