Docker Swarm vs Fleet: What are the differences?

Introduction

Docker Swarm and Fleet are two container orchestration tools used in managing and scaling containerized applications. While both tools serve the same purpose, there are key differences between them.

1. Container Management Approach: Docker Swarm is based on the concept of a swarm mode, where a group of nodes works together to form a cluster. It uses a declarative approach to define the desired state of services and handles the scheduling and distribution of containers across the cluster. On the other hand, Fleet is a distributed init system that uses a more imperative approach to launch and manage containers, relying on individual machine units to execute tasks.

2. Architecture: Docker Swarm uses a hierarchical architecture where a swarm manager controls the cluster and delegates tasks to worker nodes. This manager-worker model ensures scalability and high availability. Fleet, on the other hand, follows a decentralized architecture where each machine or node can operate independently. It uses a peer-to-peer approach for task assignment but lacks the centralized management features of Docker Swarm.

3. Ease of Use: Docker Swarm provides a built-in command-line interface (CLI) and a graphical user interface (GUI) that make it easy to set up and manage clusters. Its Docker Compose tool allows users to define and manage multi-container applications using a YAML file. Fleet, however, primarily relies on a command-line interface for task management, which requires a deeper understanding of configuration settings and scripting.

4. Features and Scalability: Docker Swarm offers a more extensive feature set, including service discovery, rolling updates, load balancing, and health checks. It supports scaling applications both horizontally and vertically, making it suitable for large-scale deployments. Fleet, on the other hand, has a more limited set of features and does not natively support advanced scaling mechanisms. It is primarily designed for smaller deployments and simpler application architectures.

5. Integration with Docker ecosystem: Docker Swarm is deeply integrated with the Docker ecosystem, allowing users to seamlessly leverage existing Docker tools and solutions. It can be integrated with Docker Registry for image management and Docker Networking for container networking. Fleet, while providing basic container management capabilities, does not offer the same level of integration with the broader Docker ecosystem.

6. Community and Support: Docker Swarm benefits from a large and active community that contributes to its development and provides support through forums, documentation, and tutorials. It also benefits from the backing and support of Docker Inc., the company behind Docker. Fleet, on the other hand, has a smaller community and fewer available resources for support and troubleshooting.

In summary, Docker Swarm and Fleet differ in their container management approach, architecture, ease of use, features and scalability, integration with the Docker ecosystem, and community support.