progress callback

Submission-flow.md

@@ -48,6 +48,7 @@ Worker gets request from broker to evaluate particular submission. Next step is
 7. after that topologically sorted execution queue is processed
     1. if execution of `inner` task fails worker will immediately stop execution and send back to broker 'internal error during execution' message
     2. execution of `execution` or `evaluation` task fails then worker stops and send back to broker 'execution failed' message
+    3. during execution worker can optionally sends current job status back to web application, this communication is described in more detailed [[communication|Overall architecture#communication]] article.
 8. when execution successfully ends results are collected from all executed tasks and written into yaml file
 9. results yaml file alongside with content of job result folder is sent back to fileserver in compressed form
 10. of course there has to be some cleaning after whole evaluation which will mostly delete content of temporarily created folders