title: how to use "per process instance" runtime strategy with Jbpm 6.4 in spring framework
body: <p>I have a business process with multi instance human task subprocess. Basically, it is leave approval process where one or many person may be involve to approve an employee leave 
  <a href="https://i.stack.imgur.com/HW3ou.png" rel="nofollow noreferrer">leave approval business process</a></p>
  
  <p>Here employee apply for leave for one or more people sign it to get task done.With Singleton strategy everything is running fine.Now I want to migrate it to "per process instance" runtime strategy. For that I modified code and added following code</p>
  
  <pre><code>this.kieSession = this.runtimeManager.getRuntimeEngine(ProcessInstanceIdContext.get()).getKieSession();
  </code></pre>
  
  <p>I have following doubts/questions:- </p>
  
  <ol>
  <li><p>Is creation of Kie Session is required only at the time starting of process ?</p></li>
  <li><p>How to extract process_instance_id for accessing kie session in future while signing the leave ?</p></li>
  <li><p>What is best approach to solve the above problem ?</p></li>
  <li><p>Is "per process instance" runtime strategy is enough or should I need to move to "per request" runtime strategy ?</p></li>
  <li><p>What is exact difference between "Singleton" and "per process instance" runtime strategy in terms of performance and resource usage ?</p></li>
  <li><p>Which one should I use if I have around 200 simultaneous user accessing my application ?</p></li>
  </ol>