functional-tester: decouple stresser from tester

This commit decouples stresser from the tester of
functional-tester. For doing it, this commit adds a new option
--stresser to etcd-tester. The option accepts two types of stresser:
"default" and "nop". If the option is "default", etcd-tester stresses
its etcd cluster with the existing stresser. If the option is "nop",
etcd-tester does nothing for stressing.

Partially fixes https://github.com/coreos/etcd/issues/6446

tools/functional-tester/etcd-tester/cluster.go

@@ -25,7 +25,6 @@ import (
 
 	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
 	"github.com/coreos/etcd/tools/functional-tester/etcd-agent/client"
-	"golang.org/x/time/rate"
 	"google.golang.org/grpc"
 )
 
@@ -53,6 +52,8 @@ type cluster struct {
 	Stressers []Stresser
 
 	Members []*member
+
+	stressBuilder stressBuilder
 }
 
 type ClusterStatus struct {
@@ -102,29 +103,9 @@ func (c *cluster) bootstrap() error {
 		}
 	}
 
-	// TODO: Too intensive stressers can panic etcd member with
-	// 'out of memory' error. Put rate limits in server side.
-	stressN := 100
 	c.Stressers = make([]Stresser, len(members))
-	limiter := rate.NewLimiter(rate.Limit(c.stressQPS), c.stressQPS)
 	for i, m := range members {
-		if c.v2Only {
-			c.Stressers[i] = &stresserV2{
-				Endpoint:       m.ClientURL,
-				keySize:        c.stressKeySize,
-				keySuffixRange: c.stressKeySuffixRange,
-				N:              stressN,
-			}
-		} else {
-			c.Stressers[i] = &stresser{
-				Endpoint:       m.grpcAddr(),
-				keyLargeSize:   c.stressKeyLargeSize,
-				keySize:        c.stressKeySize,
-				keySuffixRange: c.stressKeySuffixRange,
-				N:              stressN,
-				rateLimiter:    limiter,
-			}
-		}
+		c.Stressers[i] = c.stressBuilder(m)
 		go c.Stressers[i].Stress()
 	}
 

tools/functional-tester/etcd-tester/main.go

@@ -48,6 +48,7 @@ func main() {
 	schedCases := flag.String("schedule-cases", "", "test case schedule")
 	consistencyCheck := flag.Bool("consistency-check", true, "true to check consistency (revision, hash)")
 	isV2Only := flag.Bool("v2-only", false, "'true' to run V2 only tester.")
+	stresserType := flag.String("stresser", "default", "specify stresser (\"default\" or \"nop\").")
 	flag.Parse()
 
 	eps := strings.Split(*endpointStr, ",")
@@ -63,13 +64,18 @@ func main() {
 		agents[i].datadir = *datadir
 	}
 
+	sConfig := &stressConfig{
+		qps:            *stressQPS,
+		keyLargeSize:   int(*stressKeyLargeSize),
+		keySize:        int(*stressKeySize),
+		keySuffixRange: int(*stressKeySuffixRange),
+		v2:             *isV2Only,
+	}
+
 	c := &cluster{
-		agents:               agents,
-		v2Only:               *isV2Only,
-		stressQPS:            *stressQPS,
-		stressKeyLargeSize:   int(*stressKeyLargeSize),
-		stressKeySize:        int(*stressKeySize),
-		stressKeySuffixRange: int(*stressKeySuffixRange),
+		agents:        agents,
+		v2Only:        *isV2Only,
+		stressBuilder: newStressBuilder(*stresserType, sConfig),
 	}
 
 	if err := c.bootstrap(); err != nil {

tools/functional-tester/etcd-tester/stresser.go

@@ -369,3 +369,66 @@ func randBytes(size int) []byte {
 	}
 	return data
 }
+
+// nopStresser implements Stresser that does nothing
+type nopStresser struct {
+	start time.Time
+	qps   int
+}
+
+func (s *nopStresser) Stress() error { return nil }
+func (s *nopStresser) Cancel()       {}
+func (s *nopStresser) Report() (int, int) {
+	return int(time.Since(s.start).Seconds()) * s.qps, 0
+}
+
+type stressConfig struct {
+	qps            int
+	keyLargeSize   int
+	keySize        int
+	keySuffixRange int
+	v2             bool
+}
+
+type stressBuilder func(m *member) Stresser
+
+func newStressBuilder(s string, sc *stressConfig) stressBuilder {
+	switch s {
+	case "nop":
+		return func(*member) Stresser {
+			return &nopStresser{
+				start: time.Now(),
+				qps:   sc.qps,
+			}
+		}
+	case "default":
+		// TODO: Too intensive stressers can panic etcd member with
+		// 'out of memory' error. Put rate limits in server side.
+		stressN := 100
+		l := rate.NewLimiter(rate.Limit(sc.qps), sc.qps)
+
+		return func(m *member) Stresser {
+			if sc.v2 {
+				return &stresserV2{
+					Endpoint:       m.ClientURL,
+					keySize:        sc.keySize,
+					keySuffixRange: sc.keySuffixRange,
+					N:              stressN,
+				}
+			} else {
+				return &stresser{
+					Endpoint:       m.grpcAddr(),
+					keyLargeSize:   sc.keyLargeSize,
+					keySize:        sc.keySize,
+					keySuffixRange: sc.keySuffixRange,
+					N:              stressN,
+					rateLimiter:    l,
+				}
+			}
+		}
+	default:
+		plog.Panicf("unknown stresser type: %s\n", s)
+	}
+
+	return nil // never reach here
+}