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Introduction

Fleet is Rancher’s built-in GitOps continuous delivery system designed for managing applications across multiple Kubernetes clusters. It provides a scalable, lightweight approach to deploying applications from Git repositories to large numbers of clusters.

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What is Fleet?

Fleet is a Kubernetes-native continuous delivery solution that:
  • Deploys applications from Git repositories to multiple clusters
  • Scales to manage thousands of clusters efficiently
  • Provides GitOps workflows for declarative application management
  • Integrates natively with Rancher’s multi-cluster management

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Key Features

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Multi-Cluster Deployment

Fleet enables you to deploy applications across multiple clusters simultaneously:
  • Deploy to specific clusters or cluster groups
  • Use label selectors to target clusters dynamically
  • Manage cluster-specific configurations and overlays
  • Track deployment status across all clusters from a single interface

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GitOps-Based Workflow

Fleet follows GitOps principles where Git is the single source of truth:
  • Applications are defined declaratively in Git repositories
  • Changes to Git trigger automatic deployments
  • Provides audit trail through Git history
  • Enables rollback capabilities through Git reverts

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Fleet Architecture

Fleet consists of several key components:

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Fleet Manager

The Fleet manager runs in the Rancher management cluster and:
  • Monitors Git repositories for changes
  • Processes Fleet resources (GitRepos, Bundles, ClusterGroups)
  • Orchestrates deployments across downstream clusters
  • Aggregates deployment status from all clusters

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Fleet Agents

Fleet agents run on each managed cluster and:
  • Receive deployment instructions from the Fleet manager
  • Apply Kubernetes resources to their local cluster
  • Report deployment status back to the manager
  • Handle cluster-specific customizations

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Fleet Namespaces

Fleet uses specific namespaces for organization:
  • cattle-fleet-system: Fleet controller and management components (source:pkg/fleet/const.go:4)
  • cattle-fleet-local-system: Fleet components for the local cluster (source:pkg/fleet/const.go:5)
  • cattle-fleet-clusters-system: Cluster registration and management (source:pkg/fleet/const.go:6)
  • fleet-default: Default workspace for Fleet resources (source:pkg/fleet/const.go:12)
  • fleet-local: Local cluster workspace (source:pkg/fleet/const.go:13)

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Feature Flag

Fleet can be enabled or disabled through Rancher’s feature flag system: 
Name: fleet
Description: Install Fleet when starting Rancher
Default: true
Dynamic: false
Source: pkg/features/feature.go:47-52 Note: This is a non-dynamic feature, meaning Rancher must be restarted if the Fleet feature flag is changed.

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Fleet Workspaces

Workspaces provide multi-tenancy and isolation for Fleet resources:
  • Each workspace has its own set of GitRepos, Bundles, and clusters
  • Workspaces map to Kubernetes namespaces
  • RBAC controls can be applied per workspace
  • Projects can be associated with specific Fleet workspaces

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Use Cases

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Centralized Application Management

Manage applications across your entire fleet of clusters from a single management plane:
  • Deploy standard applications to all clusters
  • Manage cluster-specific configurations
  • Roll out updates systematically across clusters

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Environment Promotion

Implement progressive delivery across environments:
  • Deploy to dev clusters first for testing
  • Promote to staging and production environments
  • Use Git branches or tags for environment separation

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Multi-Tenant Operations

Support multiple teams with isolated workspaces:
  • Each team manages their own GitRepos and deployments
  • Workspaces provide resource isolation
  • RBAC ensures appropriate access controls

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Getting Started

To begin using Fleet:
  1. Ensure the Fleet feature flag is enabled (enabled by default)
  2. Create a GitRepo resource pointing to your application repository
  3. Define target clusters using labels or cluster groups
  4. Fleet automatically creates Bundles and deploys to matching clusters
For detailed configuration and deployment strategies, see Continuous Delivery with Fleet.

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Integration with Rancher

Fleet is deeply integrated with Rancher:
  • Automatically installed when Fleet feature is enabled
  • Uses Rancher’s cluster registry for multi-cluster operations
  • Integrates with Rancher RBAC for access control
  • Provides status visibility in Rancher UI
  • Shares cluster connectivity infrastructure
The continuous-delivery feature flag (source:pkg/features/feature.go:53-58) controls GitOps-specific components within Fleet, allowing fine-grained control over Fleet capabilities.

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Next Steps

  • Learn about Continuous Delivery with Fleet
  • Explore Fleet bundle configurations
  • Set up GitOps workflows for your applications
  • Configure cluster targeting and deployment strategies

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