Heroku worker dyno load with multiple dynos

Question

I'm trying to understand the Dyno Load section of my metrics of my app. My particular app has five worker dynos. Given that information, if I see a Load Max or Load Avg of 2 or 2.5 then I should be ok, right? With this setup my goal would be to keep the load under five (1 for each dyno)? Is that the correct way to view this?

Answer 1

The load you see in Heroku Metrics is per dyno. Each dyno sends its own load, the max being the maximum value. So expecting 5 to be a good value because you have 5 dynos isn't right.

You need to evaluate that value based on the type of dynos you have, as each of them will have more CPU shares and be able to handle more load.

Heroku recommends (here) keeping Free, Hobby and Standard dynos between 0.5 and 1.0 load. Performance-M dynos can go to 3.0 or 4.0, and PL can go up to 16.0.

See also dyno sizes and their CPU share: https://devcenter.heroku.com/articles/dyno-types