Make the current index of the round-robin balancer thread-safe

.github/workflows/go.yml

@@ -16,7 +16,8 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v3
       with:
-        go-version: 1.17
+        go-version: 1.21
+        cache: false
 
     - name: Build
       run: go build -v ./...
@@ -25,7 +26,9 @@ jobs:
       run: go test -v -race ./...
 
     - name: golangci-lint
-      uses: golangci/[email protected]
+      uses: golangci/golangci-lint-action@v3
+      with:
+        version: v1.54
 
     - name: Coverage
       run: go test -v ./... -coverprofile=coverage.txt -covermode=atomic

balancer/round_robin.go

@@ -4,10 +4,12 @@
 
 package balancer
 
+import "sync/atomic"
+
 //RoundRobin will select the server in turn from the server to proxy
 type RoundRobin struct {
 	BaseBalancer
-	i uint64
+	i atomic.Uint64
 }
 
 func init() {
@@ -17,7 +19,7 @@ func init() {
 // NewRoundRobin create new RoundRobin balancer
 func NewRoundRobin(hosts []string) Balancer {
 	return &RoundRobin{
-		i: 0,
+		i: atomic.Uint64{},
 		BaseBalancer: BaseBalancer{
 			hosts: hosts,
 		},
@@ -31,7 +33,6 @@ func (r *RoundRobin) Balance(_ string) (string, error) {
 	if len(r.hosts) == 0 {
 		return "", NoHostError
 	}
-	host := r.hosts[r.i%uint64(len(r.hosts))]
-	r.i++
+	host := r.hosts[r.i.Add(1)%uint64(len(r.hosts))]
 	return host, nil
 }

balancer/round_roubin_test.go

@@ -5,6 +5,7 @@
 package balancer
 
 import (
+	"sync/atomic"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -28,7 +29,7 @@ func TestRoundRobin_Add(t *testing.T) {
 					hosts: []string{"http://127.0.0.1:1011",
 						"http://127.0.0.1:1012", "http://127.0.0.1:1013"},
 				},
-				i: 0,
+				i: atomic.Uint64{},
 			},
 		},
 		{
@@ -41,7 +42,7 @@ func TestRoundRobin_Add(t *testing.T) {
 					hosts: []string{"http://127.0.0.1:1011",
 						"http://127.0.0.1:1012"},
 				},
-				i: 0,
+				i: atomic.Uint64{},
 			},
 		},
 	}

go.mod

@@ -1,6 +1,6 @@
 module github.com/zehuamama/balancer
 
-go 1.17
+go 1.21
 
 require (
 	github.com/gorilla/mux v1.8.0