README.md

In one terminal:

PORT=7777 go run main.go

In a separate terminal:

PORT=7778 JOIN=localhost:7777 go run main.go

Repeat as desired with additional ports, JOIN can point to one or more (comma-separated) existing nodes

go.mod

module github.com/tjcelaya/serfin

go 1.13

require (
	github.com/hashicorp/serf v0.8.5
	github.com/omeid/uconfig v0.0.0-20191124031631-f52a35b0fc4f
)

main.go

package main

import (
	"fmt"
	"log"
	"os"
	"os/signal"
	"strings"

	"github.com/hashicorp/serf/serf"
	"github.com/omeid/uconfig"
)

func main() {
	cfg := struct {
		// Join is a comma-seperated list of endpoints (host:port) to join.
		// First node in a cluster can specify no nodes to join
		Join string `env:"JOIN" default:""`

		Addr string `env:"ADDR" default:"127.0.0.1"`
		Port int    `env:"PORT" default:"7777"`
	}
	if c, err := uconfig.Classic(&cfg, nil); err != nil {
		c.Usage()
		os.Exit(1)
	}

	c := serf.DefaultConfig()
	c.NodeName = fmt.Sprintf("%s:%d", cfg.Addr, cfg.Port)
	c.MemberlistConfig.BindAddr = cfg.Addr
	c.MemberlistConfig.BindPort = cfg.Port

	s, err := serf.Create(c)
	if err != nil {
		log.Fatalf("Failed to start serf: %v", err)
	}

	if cfg.Join == ""; {
		log.Printf("No existing nodes to join, we are first in the cluster")
	} else {
		joining := strings.Split(cfg.Join, ",")
		log.Printf("Attempting to join %d existing nodes: %v", len(joining), joining)
		if reached, err := s.Join(joining, true); err != nil {
			log.Fatalf("Failed to join cluster: %+v", err)
		} else {
			log.Printf("Joined %v (reached %d)", cfg.Join, reached)
		}
	}

	// block on SIGINT / Ctrl + C
	quit := make(chan os.Signal, 1)
	signal.Notify(quit, os.Interrupt)
	<-quit

	if err := s.Leave(); err != nil {
		log.Fatalf("Failed to leave gracefully: %v", err)
	}
	finish := s.ShutdownCh()
	if err := s.Shutdown(); err != nil {
		log.Fatalf("Failed to shutdown gracefully: %v", err)
	}
	<-finish
	log.Printf("Finished shutdown, goodbye")
}