问题
I'm using New Relic for server analytics of a Heroku app. The app uses the Puma web server and MAX_THREADS is set to 1.
Why does New Relic says that I've got 4 app instances on each Heroku dyno rather than just 1?
web.1
4 app instances
web.2
4 app instances
worker.1
1 app instance
I'm thinking that an "app instance" on New Relic is the same as a thread. Or does it refer to something else?
回答1:
App instance means worker. this worker is different with heroku worker. it is process that is forked.
If you set 1 max thread, there are 4 processes(workers) and each process has 1 thread.
Check your puma's thread and worker configuration
来源：https://stackoverflow.com/questions/34468059/puma-app-instances-on-heroku