### Multiple Processes - An Example

In this example, there's a **Manager Process** that starts and controls two **Worker Processes**.

This Manager Process would probably be the one listening on the **port** in the IP. And it would transmit all the communication to the worker processes.

The only new option here is `--workers` telling Uvicorn to start 4 worker processes.

You can also see that it shows the **PID** of each process, `27365` for the parent process (this is the **process manager**) and one for each worker process: `27368`, `27369`, `27370`, and `27367`.

## Deployment Concepts

A container is running as long as the **main process** (command or program) is running.

A container normally has a **single process**, but it's also possible to start subprocesses from the main process, and that way you will have **multiple processes** in the same container.

But it's not possible to have a running container without **at least one running process**. If the main process stops, the container stops.

These examples run the server program (e.g Uvicorn), starting **a single process**, listening on all the IPs (`0.0.0.0`) on a predefined port (e.g. `80`).

This is the basic idea. But you will probably want to take care of some additional things, like:

* Security - HTTPS
* Running on startup
* Restarts
* Replication (the number of processes running)
* Memory
* Previous steps before starting

### TLS with SNI Extension

**Only one process** in the server can be listening on a specific **port** in a specific **IP address**. There could be other processes listening on other ports in the same IP address, but only one for each combination of IP address and port.

TLS (HTTPS) uses the specific port `443` by default. So that's the port we would need.

이 이미지는 주로 위에서 설명된 상황에서 유용할 것입니다: [다중 프로세스를 가지는 컨테이너와 특수한 경우들](#containers-with-multiple-processes-and-special-cases).

* <a href="https://github.com/tiangolo/uvicorn-gunicorn-fastapi-docker" class="external-link" target="_blank">tiangolo/uvicorn-gunicorn-fastapi</a>.

!!! warning "경고"

They tend to require more complex configurations, a message/job queue manager, like RabbitMQ or Redis, but they allow you to run background tasks in multiple processes, and especially, in multiple servers.

A "middleware" is a function that works with every **request** before it is processed by any specific *path operation*. And also with every **response** before returning it.

* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.
* Then it passes the **request** to be processed by the rest of the application (by some *path operation*).

このイメージは、主に上記で説明した状況で役に立つでしょう： [複数のプロセスと特殊なケースを持つコンテナ（Containers with Multiple Processes and Special Cases）](#containers-with-multiple-processes-and-special-cases)

* <a href="https://github.com/tiangolo/uvicorn-gunicorn-fastapi-docker" class="external-link" target="_blank">tiangolo/uvicorn-gunicorn-fastapi</a>.

!!! warning

## Cluster en mode Docker Swarm avec Traefik et HTTPS

Vous pouvez avoir un cluster en mode Docker Swarm configuré en quelques minutes (environ 20 min) avec un processus Traefik principal gérant HTTPS (y compris l'acquisition et le renouvellement des certificats).

En utilisant le mode Docker Swarm, vous pouvez commencer par un "cluster" d'une seule machine (il peut même s'agir