Mini Docker Orchestrator (Rust + Bollard)

This is a small container orchestrator written in Rust using the Bollard Docker SDK.
It keeps a fixed number of containers running, replaces dead ones, and supports basic rolling updates and backoff handling.

What It Does

• Connects to the local Docker engine

• Monitors containers with a specific service label

• Ensures a set number of replicas (DESIRED_REPLICAS) are always running

• Removes dead or stopped containers

• Creates new containers when needed

• Gracefully stops containers during scale-down or updates

• Adds a simple backoff mechanism to avoid constant respawning

• Supports rolling update logic using a version label

Requirements

• Rust stable toolchain

• Docker Desktop or Docker Engine running

• cargo to build/run the project

Running

cargo run

If Docker isn't running, the program will keep retrying until it becomes available.

How to Test

• Stop a container manually → the orchestrator will replace it

• Change the IMAGE constant → it will roll out new containers

• Kill Docker → orchestrator waits and reconnects when available

Configuration

Modify these constants in main.rs:

const SERVICE_NAME: &str = "..."; const IMAGE: &str = "nginx:alpine"; const DESIRED_REPLICAS: usize = 3;

Files

Everything is inside:

src/main.rs

No other external files are needed.