title: Concurrency in running Oozie workflow: how many and how to throttle
body: <p>Let us say we have a Oozie workflow that has a copy action node then a Shell action node. Can I start multiple instances of such a OOzie workflow and run them in parallel? How about the concurrency number could spike to thousands and/or even millions level. Is that possible, or even Oozie supports that high level concurrency?</p>
  
  <p>If not, then we will have to consider throttling and enforce a cap on how many concurrent Oozie workflow instances can be. We'd prefer to throttle this on server/Oozie side (basically with any out of box Oozie software functionality), not on client/callee side. For example, we have a huge launch script with lines like this. We want to run that in a single shot, then let Oozie figure out how to throttle all these instances on itself. We don't want to split it into multiple smaller chunks, then kick off one chunk at a time.</p>
  
  <pre><code>oozie job -oozie http://myhost.com:11000/oozie -config job1.properties -run
  oozie job -oozie http://myhost.com:11000/oozie -config job2.properties -run
  ......
  oozie job -oozie http://myhost.com:11000/oozie -config job1000000.properties -run
  </code></pre>