fix: ping etcd

README.md

@@ -50,8 +50,8 @@ func main() {
 	s := gocron.NewScheduler(time.UTC)
 	s.WithDistributedElector(el)
 
-	s.Every("1s").Do(func() {
-		if el.IsLeader(context.TODO()) == nil {
+	_, _ = s.Every("1s").Do(func() {
+		if el.IsLeader(context.Background()) == nil {
 			fmt.Println("the current instance is leader")
 		} else {
 			fmt.Println("the current leader is", el.GetLeaderID())

elector.go

@@ -3,13 +3,14 @@ package elector
 import (
 	"context"
 	"crypto/rand"
-	"errors"
 	"fmt"
 	mrand "math/rand"
 	"os"
 	"sync"
 	"time"
 
+	"github.com/pkg/errors"
+
 	"github.com/go-co-op/gocron"
 	clientv3 "go.etcd.io/etcd/client/v3"
 	"go.etcd.io/etcd/client/v3/concurrency"
@@ -18,6 +19,7 @@ import (
 var (
 	ErrNonLeader = errors.New("the elector is not leader")
 	ErrClosed    = errors.New("the elector is already closed")
+	ErrPingEtcd  = errors.New("ping etcd server timeout")
 )
 
 var (
@@ -64,7 +66,7 @@ func NewElectorWithClient(ctx context.Context, cli *clientv3.Client, options ...
 func newElector(ctx context.Context, cli *clientv3.Client, cfg clientv3.Config, options ...concurrency.SessionOption) (*Elector, error) {
 	var err error
 	if cli == nil {
-		cli, err = clientv3.New(cfg)
+		cli, err = clientv3.New(cfg) // async dial etcd
 		if err != nil {
 			return nil, err
 		}
@@ -80,6 +82,11 @@ func newElector(ctx context.Context, cli *clientv3.Client, cfg clientv3.Config,
 		client:  cli,
 		logger:  nullLogger,
 	}
+
+	err = el.pingEtcd("/")
+	if err != nil {
+		return nil, err
+	}
 	return el, nil
 }
 
@@ -139,6 +146,17 @@ func (e *Elector) unsetLeader(id string) {
 	e.leaderID = id
 }
 
+func (e *Elector) pingEtcd(electionPath string) error {
+	timeoutCtx, cancel := context.WithTimeout(e.ctx, 6*time.Second)
+	defer cancel()
+
+	_, _ = e.client.KV.Get(timeoutCtx, electionPath)
+	if timeoutCtx.Err() == context.DeadlineExceeded {
+		return ErrPingEtcd
+	}
+	return nil
+}
+
 // Start Start the election.
 // This method will keep trying the election. When the election is successful, set isleader to true.
 // If it fails, the election directory will be monitored until the election is successful.

elector_test.go

@@ -17,6 +17,18 @@ var (
 	testElectionPath = "/gocron/elector/"
 )
 
+func TestGocronDialTimeout(t *testing.T) {
+	start := time.Now()
+	_, err := NewElector(context.Background(), Config{
+		Endpoints: []string{"http://127.0.0.1:2000"}, // invalid etcd
+	})
+	assert.Equal(t, ErrPingEtcd, err)
+
+	// 5< 6 < 7
+	assert.Greater(t, int(time.Since(start).Seconds()), 5)
+	assert.Less(t, int(time.Since(start).Seconds()), 8)
+}
+
 func TestGocronWithElector(t *testing.T) {
 	el, err := NewElector(context.Background(), testConfig, WithTTL(1))
 	assert.Equal(t, nil, err)

go.mod

@@ -15,7 +15,7 @@ require (
 	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/golang/protobuf v1.5.3 // indirect
 	github.com/google/uuid v1.3.1 // indirect
-	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pkg/errors v0.9.1
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/robfig/cron/v3 v3.0.1 // indirect
 	go.uber.org/atomic v1.9.0 // indirect