Raft: Check suspect info once per suspect interval

Today's existing suspect logic has a periodic checker, which checks
every 10s if the Raft cluster still has quorum.  If the cluster has lost
quorum, it marks the time this event begins, then, every 10s checks to
see if 'enough' time has elapsed since the quorum was lost to suspect
that the OSN has been evicted.

If the OSN has not been evicted, or cannot determine its eviction
status, then every 10s the OSN attempts to re-check its suspicion
status, which can lead to large volumes of network traffic, especially
in significiantly multichannel environments.

This commit modifies the logic to track the number of times that the
suspect checking logic has actually executed, to ensure that we check no
more than once every suspect interval (by default every 10m, instead of
every 10s).

Signed-off-by: Jason Yellick <jyellick@us.ibm.com>

orderer/consensus/etcdraft/chain.go

@@ -369,6 +369,7 @@ func (c *Chain) Start() {
 	c.periodicChecker = &PeriodicCheck{
 		Logger:        c.logger,
 		Report:        es.confirmSuspicion,
+		ReportCleared: es.clearSuspicion,
 		CheckInterval: interval,
 		Condition:     c.suspectEviction,
 	}

orderer/consensus/etcdraft/eviction.go

@@ -26,6 +26,7 @@ type PeriodicCheck struct {
 	CheckInterval       time.Duration
 	Condition           func() bool
 	Report              func(cumulativePeriod time.Duration)
+	ReportCleared       func()
 	conditionHoldsSince time.Time
 	once                sync.Once // Used to prevent double initialization
 	stopped             uint32
@@ -60,6 +61,9 @@ func (pc *PeriodicCheck) check() {
 }
 
 func (pc *PeriodicCheck) conditionNotFulfilled() {
+	if pc.ReportCleared != nil && !pc.conditionHoldsSince.IsZero() {
+		pc.ReportCleared()
+	}
 	pc.conditionHoldsSince = time.Time{}
 }
 
@@ -81,12 +85,20 @@ type evictionSuspector struct {
 	writeBlock                 func(block *common.Block) error
 	triggerCatchUp             func(sn *raftpb.Snapshot)
 	halted                     bool
+	timesTriggered             int
+}
+
+func (es *evictionSuspector) clearSuspicion() {
+	es.timesTriggered = 0
 }
 
 func (es *evictionSuspector) confirmSuspicion(cumulativeSuspicion time.Duration) {
-	if es.evictionSuspicionThreshold > cumulativeSuspicion || es.halted {
+	// The goal here is to only execute the body of the function once every es.evictionSuspicionThreshold
+	if es.evictionSuspicionThreshold*time.Duration(es.timesTriggered+1) > cumulativeSuspicion || es.halted {
 		return
 	}
+	es.timesTriggered++
+
 	es.logger.Infof("Suspecting our own eviction from the channel for %v", cumulativeSuspicion)
 	puller, err := es.createPuller()
 	if err != nil {

orderer/consensus/etcdraft/eviction_test.go

@@ -48,11 +48,18 @@ func TestPeriodicCheck(t *testing.T) {
 		reports <- duration
 	}
 
+	clears := make(chan struct{}, 1000)
+
+	reportCleared := func() {
+		clears <- struct{}{}
+	}
+
 	check := &PeriodicCheck{
 		Logger:        flogging.MustGetLogger("test"),
 		Condition:     condition,
 		CheckInterval: time.Millisecond,
 		Report:        report,
+		ReportCleared: reportCleared,
 	}
 
 	go check.Run()
@@ -85,6 +92,9 @@ func TestPeriodicCheck(t *testing.T) {
 		}
 	}
 
+	g.Eventually(clears).Should(gomega.Receive())
+	g.Consistently(clears).ShouldNot(gomega.Receive())
+
 	// ensure the checks have been made
 	checksDoneSoFar := atomic.LoadUint32(&checkNum)
 	g.Consistently(reports, time.Second*2, time.Millisecond).Should(gomega.BeEmpty())
@@ -107,6 +117,7 @@ func TestPeriodicCheck(t *testing.T) {
 	time.Sleep(check.CheckInterval * 50)
 	// Ensure that we cease checking the condition, hence the PeriodicCheck is stopped.
 	g.Expect(atomic.LoadUint32(&checkNum)).To(gomega.BeNumerically("<", checkCountAfterStop+2))
+	g.Consistently(clears).ShouldNot(gomega.Receive())
 }
 
 func TestEvictionSuspector(t *testing.T) {
@@ -137,13 +148,20 @@ func TestEvictionSuspector(t *testing.T) {
 		blockPuller                 BlockPuller
 		blockPullerErr              error
 		height                      uint64
+		timesTriggered              int
 		halt                        func()
 	}{
 		{
 			description:                "suspected time is lower than threshold",
 			evictionSuspicionThreshold: 11 * time.Minute,
 			halt:                       t.Fail,
 		},
+		{
+			description:                "timesTriggered multiplier prevents threshold",
+			evictionSuspicionThreshold: 6 * time.Minute,
+			timesTriggered:             1,
+			halt:                       t.Fail,
+		},
 		{
 			description:                "puller creation fails",
 			evictionSuspicionThreshold: 10*time.Minute - time.Second,
@@ -219,6 +237,7 @@ func TestEvictionSuspector(t *testing.T) {
 				},
 				logger:         flogging.MustGetLogger("test"),
 				triggerCatchUp: func(sn *raftpb.Snapshot) {},
+				timesTriggered: testCase.timesTriggered,
 			}
 
 			foundExpectedLog := testCase.expectedLog == ""