CODEWITHSUNDEEP
amazon-web-servicesherokumicroservices
Maciej Treder
Maciej Treder

Reputation: 12350

Can the same dyno run multiple processes?

I am creating small app running multiple microservices. I would like to have this app available 24/7, so free dyno hours are not enough for me. If I upgrade to a hobby plan I would get 10 Process Types.

Can I run another microservice on each of the processes (web), or does Heroku give me the ability only to install one web process per dyno, and the other 10 process types are for scaling my app? In other words, If i need 6 microservices running 24/7 should I buy 6 hobby dynos?

Upvotes: 3

Views: 4119

Answers (3)

user670908
user670908

Reputation: 321

There's RUNIT buildpack which makes it easy to combine multiple processes within a single dyno - as long as they all fit within your dyno memory limit (512M for a Hobby dyno).

You still have only one HTTP endpoint per Heroku app, which means your microservices will need to communicate via queues, pub/sub or some RPC hub (like deepstream.io).

Upvotes: 4

qix
qix

Reputation: 7952

Heroku's default model is to map a process type to its own dyno: https://devcenter.heroku.com/articles/procfile states

"Every dyno in your application will belong to one of the process types, and will begin executing by running the command associated with that process type."

e.g. heroku ps:scale worker=1 for a type of worker.

Other people have written about how to use foreman or Honcho to run multiple python processes in a single dyno, which utilize a secondary Procfile and possibly other slug setup in a post_compile step. Presumably you could do something similar depending on your chosen language and its buildpack; the official buildpack API doesn't list this step though :/. That said, given Heroku's base Ubuntu stacks, you may be able to get away with a web: script.sh to do any setup and exec of processes.

For grouping multiple processes in a Docker container, you could check out https://runnable.com/docker/rails/run-multiple-processes-in-a-container, which relies again on a custom CMD [ "/start.sh" ]. Note that it's contrary to Docker's single-­process-­per-­container philosophy, and can give you more headaches e.g. around forwarding signals to child processes, an ugly Dockerfile to setup all microservices, etc. (If you do decide to use multiple containers, Heroku has a writeup on using Docker Compose for local dev.)

Also, don't forget you're bounded by the performance of your dyno and the process/thread limits.

Of course, multiple processes in a given dyno is generally not recommended for non-toy production or long term dev maintenance. ;)

Upvotes: 3

Yoni Rabinovitch
Yoni Rabinovitch

Reputation: 5261

You can only have 1 web process type. You can horizontally scale your web process to run on multiple dynos ("horizontal scalability"), however you will need to upgrade to at least standard-1x dyno types to do that (i.e. you can only run 1 web dyno instance if you are using free or hobby dyno types).

However, in addition to your web process, you can instantiate multiple additional process types (e.g. "worker" processes). These will NOT be able to listen on HTTP/S requests from your clients, but can be used for offloading long-running jobs from your web process.

So, if you map each of your 4-6 microservices to a different Process Type in your Procfile, and if your microservices are not themselves web servers, you might be able to make do with hobby dynos.

Upvotes: 6

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