Avoiding the execution of a job chain when an order is already running in the chain

 <?xml version="1.0" encoding="ISO-8859-1"?>
 
 <job_chain max_orders="1">
    <job_chain_node state="100"
                    job="jobsSample_1"
                    next_state="200"
                    error_state="error"/>
    <job_chain_node state="200"
                    job="jobsSample_2"
                    next_state="success"/>
    <job_chain_node state="success"/>
    <job_chain_node state="error"/>
 </job_chain>