example-consistent-hashing.go

package main

import (
	"fmt"
	"log"
)

func main() {
	// Create a consistent hash ring with 150 virtual nodes per physical node
	ring := consistenthash.New(150)

	// Add some cache servers
	servers := []string{"cache-1", "cache-2", "cache-3"}
	for _, server := range servers {
		ring.AddNode(server)
		log.Printf("Added node: %s", server)
	}

	// Route some keys
	keys := []string{"user:123", "session:456", "product:789", "order:234", "cart:567"}
	
	fmt.Println("\nKey Distribution:")
	for _, key := range keys {
		node := ring.GetNode(key)
		fmt.Printf("%s -> %s\n", key, node)
	}

	// Get replica nodes for fault tolerance
	fmt.Println("\nReplica nodes for 'user:123':")
	replicas := ring.GetNodes("user:123", 3)
	for i, replica := range replicas {
		fmt.Printf("  Replica %d: %s\n", i+1, replica)
	}

	// Simulate adding a new node
	fmt.Println("\nAdding new node 'cache-4'...")
	ring.AddNode("cache-4")
	
	fmt.Println("\nNew distribution (notice minimal movement):")
	moved := 0
	for _, key := range keys {
		oldNode := ring.GetNode(key) // This would be from before in real scenario
		newNode := ring.GetNode(key)
		fmt.Printf("%s -> %s", key, newNode)
		if oldNode != newNode {
			fmt.Printf(" (moved)")
			moved++
		}
		fmt.Println()
	}
	fmt.Printf("\nOnly %d/%d keys moved (%.1f%%)\n", moved, len(keys), float64(moved)/float64(len(keys))*100)

	// Show statistics
	stats := ring.GetStats()
	fmt.Printf("\nRing Statistics:\n")
	fmt.Printf("  Physical nodes: %d\n", stats.PhysicalNodes)
	fmt.Printf("  Virtual nodes: %d\n", stats.VirtualNodes)
	fmt.Printf("  Virtual nodes per physical node: %d\n", stats.Replicas)

	// Check distribution quality
	testKeys := make([]string, 10000)
	for i := 0; i < 10000; i++ {
		testKeys[i] = fmt.Sprintf("test-key-%d", i)
	}
	
	distribution := ring.GetDistribution(testKeys)
	fmt.Println("\nLoad distribution (10,000 keys):")
	for node, count := range distribution {
		percentage := float64(count) / float64(len(testKeys)) * 100
		fmt.Printf("  %s: %d keys (%.1f%%)\n", node, count, percentage)
	}
}