How to process orders in an expected sequence

Scope

Use Case:
- Consider the situation where a number of orders are added in an arbitrary sequence and at arbitrary points in time to a job chain - either from a file order source watching incoming files, from ad hoc orders or from permanent orders. The orders should then be processed serially according to predefined criteria.
- Each order comes either:
  - with a parameter that specifies a numeric sequence,
  - with a parameter that specifies a business date, e.g. for data files that are referenced by the order and that should be loaded to a data warehouse in sequence of the business dates,
  - without parameters and should be processed in alphabetical or numerical sequence according to its order ID.
- Orders should be processed strictly in the required sequence - either ascending or descending. If an incoming order does not provide the expected value then it should be suspended and the job chain waits for an order with the expected value to arrive. After arrival of an order with the expected value all suspended orders should then be checked to see if they provide the expected value required for the successor order.
Solution Outline:
- A single job is added at the start of a job chain. This job:
  - checks for exepected values and suspends incoming orders until an order with the expected value arrives,
  - moves orders that match expected values to the next job node in the job chain and rechecks the expected value of any suspended orders.
References
- SourceForge Forum Discussion Thread

Solution

Download expect_orders.zip
Extract the archive to any folder within the ./config/live folder of your JobScheduler installation.
The archive will extract the files to a folder expect_orders.
You can store the sample files in any folder you like - the solution does not make use of specific folder names or job names.

Pattern

Implementation

Components

The solution implements a job expect that can be added at the start of a job chain.
- This job implements a spooler_process() function that checks if an order matches the expected value and that suspends non-matching orders.
  - Expected values can be provided by incoming orders:
    - using parameters:
      - each incoming order is assumed to provide a parameter that contains the expected value.
        Example for use with oder parameter:
        business_date = 2015-11-01
      - the name of the incoming orders' parameter is specified as the value of the expect job's control_order_expected_parameter parameter.
        Example for use with expect job parameter:
        control_order_expected_parameter= business_date
    - without parameters:
      - the job will expect a numeric order ID to be provided and increments the order ID to calculate the next expected value.
  - For expected values a function has to be provided that calculates the next expected value:
    - the function is specified by the expect job's control_order_expected_value_function parameter. The function has been implemented with JavaScript code that returns the next expected value according to the current value that is provided with the currentValue variable:
      - Example for numeric calculation:
        parseInt(currentValue) + 1
        Explanation: the function parses the current expected numeric value and returns the incremented value.
      - Example for date calculation:
        (new Date( (new Date(currentValue)).setDate( (new Date(currentValue)).getDate()+1 ) )).toISOString().substring(0,10);
        Explanation: the function accepts the current date value, adds one day and returns the date in ISO format, e.g. 2015-11-01
  - A default value can be provided for the expected values that is used to check the expected value of the first incoming order:
    - the default value can be specified by the expect job's control_order_expected_default_value parameter.
      - Example for use with numeric default value:
        control_order_expected_default_value = 1
      - Example for use with date default value:
        control_order_expected_default_value = 2015-11-01
    - without specification of a default value the value of the first order processed by the expect job will be used as a default.
- This job is configured for a single task, i.e. it executes incoming orders sequentially.
- Having received an order with the expected value this job moves that order to the next job node in the job chain and activates any suspended orders for rechecking to see if they provide the next expected value.
The solution automatically creates a control order that is used to store the next expected value.
- The name of the control order is generated from the "control_order_" prefix and the state that the expect job node is assigned.
- The control order is suspended and not processed by subsequent job nodes. Its only purpose is to carry the next expected value for use of the solution with JobScheduler Agents and cluster members.
The sample makes use of a job chain job_chain_expected_orders This chain includes the job nodes for the expect job and a hello job. The job chain accepts ad hoc orders that are added using JOC and can easily be modified to watch for incoming files and create an order for each file.
Hint: to re-use the expect job you can:
- store the job in a central folder and reference the job in individual job chains.
- move the job's JavaScript code to a central location and use an appropriate <include> element for individual job scripts.

Job expect

var jobChainPath = null;
var jobChainNodeState = null;

var orderExpectedValue = null;
var orderExpectedDefaultValue = null;

var orderExpectedValueFunction = "parseInt(currentValue) + 1";
var controlOrderPrefix = "control_order_";
var controlOrderID = null;

function executeXML( command ) {
  var rc = false;

  spooler_log.debug( ".... executing xml command: " + command );
  var response = spooler.execute_xml( command );
  var xmlDOM = new Packages.sos.xml.SOSXMLXPath( new java.lang.StringBuffer( response ) );
  var errorCode = xmlDOM.selectSingleNodeValue( "//ERROR/@code" );
  var errorText = xmlDOM.selectSingleNodeValue( "//ERROR/@text" );
  if ( errorCode || errorText ) {
    spooler_log.error( ".... xml response: errorCode=" + errorCode + ", errorText=" + errorText );
  } else {
    rc = xmlDOM;
  }

  return rc;
}

function getOrderExpectedValue() {
  if (orderExpectedValue == null) {
    orderDOM = executeXML( "<show_order job_chain='" + jobChainPath + "' order='" + controlOrderID + "' what='payload'/>" );
    if ( orderDOM ) {
      orderExpectedValue = orderDOM.selectSingleNodeValue( "/spooler/answer/order/payload/params/param[@name = '" + controlOrderID + "']/@value" );
    }
  }

  if ( !orderExpectedValue ) {
    orderExpectedValue = orderExpectedDefaultValue;
    spooler_log.info( ".... getOrderExpectedValue(): " + orderExpectedValue + " (default)" );
  } else {
    spooler_log.info( ".... getOrderExpectedValue(): " + orderExpectedValue );
  }

  return orderExpectedValue;
}

function setOrderExpectedValue( expectedValue ) {
  spooler_log.info( ".... setOrderExpectedValue(): " + expectedValue );
  var rc = true;
  orderExpectedValue = expectedValue;

  // check existence of control order, if historic then its state does not match the job node state
  var orderDOM = executeXML( "<show_order job_chain='" + jobChainPath + "' order='" + controlOrderID + "' what='payload'/>" );
  if ( orderDOM ) {
    var orderState = orderDOM.selectSingleNodeValue( "/spooler/answer/order/@state" );
    if (!orderState || orderState != jobChainNodeState) {
      rc = false;
    }
  } else {
    rc = false;
  }

  // add or modify control order
  if (!rc) {
    orderDOM = executeXML( "<add_order job_chain='" + jobChainPath + "' id='" + controlOrderID + "' state='" + jobChainNodeState + "' suspended='yes'><params><param name='" + controlOrderID + "' value='" + orderExpectedValue + "'/></params><run_time/></add_order>" );
  } else {
    orderDOM = executeXML( "<modify_order job_chain='" + jobChainPath + "' order='" + controlOrderID + "' state='" + jobChainNodeState + "' suspended='yes'><params><param name='" + controlOrderID + "' value='" + orderExpectedValue + "'/></params><run_time/></modify_order>" );
  }
  spooler_job.state_text = "next expected value: " + orderExpectedValue;
}

function calculateOrderExpectedValue( currentValue ) {
  // calculate next date for a date parameter
  // var expectedValue = (new Date( (new Date(currentValue)).setDate( (new Date(currentValue)).getDate()+1 ) )).toISOString().substring(0,10);
  // calculate increment for a numeric parameter or order id
  // var expectedValue = parseInt(currentValue) + 1;

  var expectedValue = eval( orderExpectedValueFunction );
  return expectedValue;
}

function spooler_init() {
  jobChainPath = spooler_task.order.job_chain.path;
  jobChainNodeState = spooler_task.order.job_chain_node.state;
  controlOrderID = controlOrderPrefix + spooler_task.order.job_chain_node.state;

  return true;
}

function spooler_process() {
  var rc = true;

  // control order is always suspended
  if (spooler_task.order.id == controlOrderID) {
    spooler_log.info( ".. control order identified, processing suspended" );
    suspendOrder();
    return rc;
  }

  // merge parameters from task and order
  var params = spooler.create_variable_set();
  params.merge( spooler_task.params );
  params.merge( spooler_task.order.params );

  // get expected value from a parameter name or from the Order ID
  spooler_log.info( ".. control parameter for expected value is looked up: " + controlOrderPrefix + "expected_parameter" );
  var expectedParameter = params.value( controlOrderPrefix + "expected_parameter" );
  if (expectedParameter) {
    var currentValue = params.value( expectedParameter );
    spooler_log.info( ".. current value is used from control parameter [" + expectedParameter + "]: " + currentValue );
  } else {
    var currentValue = spooler_task.order.id;
    spooler_log.info( ".. current value is used from order id: " + currentValue );
  }

  // get expected default value from a parameter or from the order id
  if (!orderExpectedDefaultValue) {
    orderExpectedDefaultValue = params.value( controlOrderPrefix + "expected_default_value" );
    if (orderExpectedDefaultValue) {
      spooler_log.info( ".. default value is used from control parameter [" + controlOrderPrefix + "expected_default_value]: " + orderExpectedDefaultValue );
    } else {
      spooler_log.info( ".. default value is used from order id: " + spooler_task.order.id );
      orderExpectedDefaultValue = spooler_task.order.id;
    }
  }

  // get expected value calculation function
  var expectedValueFunction = params.value( controlOrderPrefix + "expected_value_function" );
  if (expectedValueFunction) {
    orderExpectedValueFunction = expectedValueFunction;
    spooler_log.info( ".. using expected value function: " + orderExpectedValueFunction );
  } else {
    spooler_log.info( ".. using expected value default function: " + orderExpectedValueFunction );
  }

  // check if order value matches expectation
  if ( getOrderExpectedValue() == currentValue ) {
    // after processing of the current order all suspended orders are activated
    spooler_log.info( ".. current order provides expected value: " + getOrderExpectedValue() );
    activateSuspendedOrders();
    setOrderExpectedValue( calculateOrderExpectedValue( getOrderExpectedValue() ) );
  } else {
    // suspend non-matching order
    spooler_log.info( ".. suspending current order: expected value=" + getOrderExpectedValue() + ", current value=" + currentValue );
    suspendOrder();
  }

  return rc;
}

function suspendOrder() {
    spooler_task.order.suspended = true;
    spooler_task.order.state = jobChainNodeState;
}

function activateSuspendedOrders() {
  var rc = true;
  var orderList = Array();

  // select suspended orders of the current job node
  var orderDOM = executeXML( "<show_job_chain job_chain='" + jobChainPath + "' what='job_chain_orders'/>" );
  var orderNodes = orderDOM.selectNodeList( "/spooler/answer/job_chain/job_chain_node[@state = '" + jobChainNodeState + "']/order_queue/order[@suspended = 'yes']" );

  // traverse order list and add orders to sort array
  for( orderIndex=0; orderIndex<orderNodes.getLength(); orderIndex++ ) {
    var orderNode = orderNodes.item(orderIndex);
    var orderID = orderDOM.selectSingleNodeValue( orderNode, "@id" );
    if (orderID == null || controlOrderID) {
      continue;
    }
    spooler_log.info( ".... suspended order found: " + orderID );
    orderList.push( orderID );
  }

  // alphabetical string sort
  orderList.sort(function(a, b){return (a > b) - (a < b) });
  // numeric sort
  // orderList.sort(function(a, b){return b - a) });

  for(i=0; i<orderList.length; i++) {
    spooler_log.info( ".... activating order: " + orderList[i] );
    orderDOM = executeXML( "<modify_order job_chain='" + jobChainPath + "' order='" + orderList[i] + "' state='" + jobChainNodeState + "' suspended='no'/>" );
    if ( !orderDOM ) {
      rc = false;
    }  
  }

  return rc;
}

Usage

Add the orders to the job_chain_expect_orders job chain. For your convenience the orders 1, 2 and 3 are provided with the sample.
- Each order uses a sequence parameter with a sequential number such as 1, 2, 3.
- The expect job uses the parameters:
  - control_order_expected_parameter with the value: sequence
  - control_order_expected_default_value with the value: 1
  - control_order_expected_value_function with the value: parseInt(currentValue) + 1
Start order 1 that matches the expected value (parameter sequence=1):
- The order will be processed and then moved to the next_job job.
- A control order named control_order_expect will be dynamically generated and suspended. This order contains the next expected value (parameter control_order_expect=2)
Start order 3 that does not match the expected value (parameter sequence=3)
- The order will be suspended.
- The control order with the expected value (parameter control_order_expect=2) will remain unchanged.
Start order 2 that matches the expected value (parameter sequence=2:
- Order 2 will be processed and moved to the next_job job.
  - The control order will be automatically modified to carry the next expected value (parameter control_order_expect=3).
- Order 3 will be processed and then moved to the next_job job.
  - The control order will be automatically modified to carry the next expected value (parameter control_order_expect=4).
For use with a date sequence instead of a numeric sequence:
- the orders 1, 2, 3 carry a second parameter business_date with values in an ISO date format.
- the expect job carries sample parameters (prefixed with sample_) that can be activated (renamed) to work with the business_date parameter instead of the sequence parameter of the incoming orders .

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