Add process-compose driver in osrdyne

[leovalais]

Required to dev on editoast for macs (no Docker host networking available).

osrd/osrdyne/src/drivers/process_compose.rs

Lines 1 to 60 in 76a8292

	//! A driver to manage workers using [process-compose](https://github.com/F1bonacc1/process-compose) REST API.
	//!
	//! This driver is especially useful for backend development on systems where Docker host networking is not available (👀 macOS).
	//!
	//! This driver is primarily intended for development purposes. It is not recommended to use it in production.
	//! Multiple process-compose instances are not supported.
	//!
	//! # Implementation details
	//!
	//! ## Spawning workers
	//!
	//! `process-compose` configuration is read at startup and cannot be modified while `process-compose` is running.
	//! This has several unfortunate consequences on how the driver works, especially on the scaling part. Indeed,
	//! we cant just edit the YAML in the driver as there's no way to reload the configuration.
	//!
	//! process-compose allows a process to be scaled (`sh$ process-compose process scale <process> <count>`). However,
	//! we cannot set the configuration of a replicated process. Each one of them has to follow the configuration defined
	//! in `process-compose.yaml`. **Including environment variables**. This is particularly problematic for the driver
	//! which has to set a different WORKER_{ID,KEY,AMQP_URI} for each process.
	//!
	//! We overcome this by reading the values of the WORKER_* variables from tmp files when the process start. These files
	//! are written by the driver just before a process starts.
	//!
	//! ## Identifying workers
	//!
	//! Unlike Docker or Kube, process-compose doesn't let us tag each process individually. We have to store in the driver
	//! a mapping {PID => (Key, Uuid)} to keep track of which process is assigned to which worker key.
	//!
	//! ## Dealing with `process-compose process scale` behaviour
	//!
	//! process-compose scaling may rename the process being scale. For example, if when starting PC whe have:
	//!
	//! ```
	//! core
	//! editoast
	//! front
	//! # ...
	//! ```
	//!
	//! and we scale `core` to 3 (`process-compose process scale core 3`), we will have:
	//!
	//! ```
	//! core-0
	//! core-1
	//! core-2
	//! editoast
	//! front
	//! ```
	//!
	//! Note how the original `core` process is now named `core-0`.
	//! Now, if we want to scale even more, `process-compose process scale core 5`, we will fail since `core` doesn't exist anymore.
	//! We have to run `process-compose process scale core-0 5` instead.
	//!
	//! The reverse applies when scaling down: `process-compose process scale core-0 1` will rename `core-0` to `core`.
	//!
	//! # Known limitations
	//!
	//! * Restarting the osrdyne process but not the other will spawn new workers for each message queue (the driver lost
	//! its internal mapping).
	//! * The driver doesn't cleanup disabled or errored workers.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 0% with 227 lines in your changes missing coverage. Please review.

Project coverage is 36.93%. Comparing base (3eecd56) to head (e77107d).
Report is 127 commits behind head on dev.

Files with missing lines	Patch %	Lines
osrdyne/src/drivers/process_compose.rs	0.00%	219 Missing ⚠️
osrdyne/src/drivers/docker.rs	0.00%	2 Missing ⚠️
osrdyne/src/drivers/kubernetes.rs	0.00%	2 Missing ⚠️
osrdyne/src/drivers/noop.rs	0.00%	2 Missing ⚠️
osrdyne/src/drivers/worker_driver.rs	0.00%	1 Missing ⚠️
osrdyne/src/pool.rs	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff              @@
##                dev    #8573      +/-   ##
============================================
+ Coverage     36.84%   36.93%   +0.08%     
- Complexity     2175     2212      +37     
============================================
  Files          1279     1257      -22     
  Lines        118794   114293    -4501     
  Branches       3188     3188              
============================================
- Hits          43775    42213    -1562     
+ Misses        73134    70184    -2950     
- Partials       1885     1896      +11     

Flag	Coverage Δ
core	74.79% <ø> (-0.08%)	⬇️
editoast	72.13% <ø> (+6.03%)	⬆️
front	14.96% <ø> (-0.89%)	⬇️
gateway	2.20% <ø> (ø)
osrdyne	2.60% <0.00%> (-0.11%)	⬇️
railjson_generator	87.49% <ø> (ø)
tests	86.37% <ø> (+13.44%)	⬆️

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