Cron starts when it's already running

[kanduvisla]

I noticed that when I start a cron that's already running it will run again. For example: I have a task that takes 15 minutes, but the cron executes it's every 5 minutes. In the database the cron gets the status running and the other scheduled jobs have pending. But after 5 minutes, the other job (with the same code) also starts to run. So now I have the same job running twice!

Preconditions

1. Magento 2.1.7

Steps to reproduce

1. Create a cron that takes a while (for example, sleep 15 minutes)
2. Schedule it to run every 5 minutes

Expected result

The other jobs should wait for the first job to complete, even though they are scheduled to run every 5 minutes.

Actual result

The new job starts, ignoring the fact that it's already running...

I'm not sure if this is intended behavior or a bug. Am I expected to create my own lock / flag for this?

[scottsb]

Note to anybody working on this: ticket #10279 was closed as a dup of this but contains additional details about the root cause that I had already tracked down.

[magento-engcom-team]

@kanduvisla, thank you for your report.
We've created internal ticket(s) MAGETWO-80790 to track progress on the issue.