add a configuration option for specifying a worker heartbeat interval

[bioker]

No description provided.

[bioker]

I have noticed that there is no option to configure this parameter.

I have faced a situation when the heartbeat fails but workers seem to be healthy while doing this lab project: https://github.com/bioker/mysql-lab/blob/f85ea857d0c4b29261569eadcca6b5344ac7eed1/docker-compose.yaml#L4.

Running the project with the custom docker image I build from my version shows that the increased heartbeat interval helps to avoid such problems and the test still works well.

Maybe it's worth checking why it fails in the first place, but it seems harder than adding this parameter and I suppose it can be useful in some flaky environments anyway so here is the PR.
I hope you will find it useful too.

Also seems to be related to the following issues:
#1787
#1843

[bioker]

Ah, have followed the issue history and noticed this feature request so linking it also:
#1897

[bioker]

This change represents how I have used the updated version: https://github.com/bioker/mysql-lab/commit/eedbb5a31f717acbc128ebf4ba3a05fe88d01458

[cyberw]

Hmm... those values are already customizable in the locustfile, and I'm not sure they are worthy of a command line setting.

from locust import runners
runners.HEARTBEAT_INTERVAL = 2

[bioker]

Ok, I see, thanks for the example