topic Re: How to handle a race condition signaling an Execution in Alfresco Forum

How to handle a race condition signaling an Execution

blezek — Fri, 17 Feb 2017 14:08:05 GMT

Hi, We start long-running workflows that wait for a signal. When certain events happen, we signal the workflow by searching for the list of Executions waiting on the signal (and some other criteria). This can lead to race conditions because the incoming events can come in short order. Here is ex

Re: How to handle a race condition signaling an Execution

gdharley — Fri, 17 Feb 2017 22:50:35 GMT

Dan,

you have to change your design to decouple the signal send and receive logic.

Put the signals onto a queue and then have the receiver loop through each signal/message in it's own time. Before "stopping" at the next "signal" look to see if there is already a message on the queue and process it immediately.

What you describe is a very typical issue when the processing time for signals can exceed the interval between received signals.

Greg

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Re: How to handle a race condition signaling an Execution

blezek — Thu, 23 Feb 2017 13:28:43 GMT

Greg, Yup, that's what I figured you'd say... 😃 We will document that signal are delivered "best effort" and that workflows should not depend on them being delivered. The notification logic adds the new information into a workflow variable and continues. That logic also locks to have a single thread, so we don't clobber the workflow variables.

Thanks much,

-dan