leaderelection

pkg/k8s/leaderelection

Pure leader election library wrapping k8s.io/client-go/tools/leaderelection.

Overview

Provides a clean interface for leader election using Kubernetes Lease resources. This is a pure library with no dependencies on the event bus or controller coordination logic.

Usage

import (
    "context"
    "log/slog"
    "time"

    "k8s.io/client-go/kubernetes"
    "haptic/pkg/k8s/leaderelection"
)

// Create configuration
config := &leaderelection.Config{
    Enabled:         true,
    Identity:        "pod-1",
    LeaseName:       "my-app-leader",
    LeaseNamespace:  "default",
    LeaseDuration:   15 * time.Second,
    RenewDeadline:   10 * time.Second,
    RetryPeriod:     2 * time.Second,
    ReleaseOnCancel: true,
}

// Define callbacks
callbacks := leaderelection.Callbacks{
    OnStartedLeading: func(ctx context.Context) {
        log.Println("Became leader")
        // Start leader-only components
    },
    OnStoppedLeading: func() {
        log.Println("Lost leadership")
        // Stop leader-only components
    },
    OnNewLeader: func(identity string) {
        log.Printf("New leader: %s", identity)
    },
}

// Create elector
elector, err := leaderelection.New(config, clientset, callbacks, logger)
if err != nil {
    panic(err)
}

// Start leader election (blocks until context cancelled)
ctx := context.Background()
elector.Start(ctx)

API

Config

Configuration for leader election:

• Enabled: Whether leader election is active
• Identity: Unique identifier (usually pod name)
• LeaseName: Name of Lease resource
• LeaseNamespace: Namespace of Lease resource
• LeaseDuration: How long non-leaders wait before forcing acquisition
• RenewDeadline: How long leader retries before giving up
• RetryPeriod: Wait duration between retry attempts
• ReleaseOnCancel: Release leadership when context cancelled

Callbacks

Event callbacks:

• OnStartedLeading(ctx): Called when becoming leader
• OnStoppedLeading(): Called when losing leadership
• OnNewLeader(identity): Called when new leader observed

Elector

Main leader election type:

• New(): Create new elector
• Start(ctx): Start leader election loop (blocks)
• IsLeader(): Check if currently leader
• GetLeader(): Get current leader identity

Thread Safety

All public methods are thread-safe and can be called concurrently.