[FAB-5313] Leader election yield if deliver unavailable

This commit makes the peer relinquish its leadership if it can't
connect to the ordering service.

Change-Id: I5fe679d5f23e539828fea4a9398c7dd4d9fd0f93
Signed-off-by: yacovm <[email protected]>

Author: yacovm

core/deliverservice/deliveryclient.go

@@ -34,12 +34,20 @@ var (
 	reConnectBackoffThreshold   = float64(time.Hour)
 )
 
+// SetReconnectTotalTimeThreshold sets the total time the delivery service
+// may spend in reconnection attempts until its retry logic gives up
+// and returns an error
+func SetReconnectTotalTimeThreshold(duration time.Duration) {
+	reConnectTotalTimeThreshold = duration
+}
+
 // DeliverService used to communicate with orderers to obtain
 // new blocks and send them to the committer service
 type DeliverService interface {
 	// StartDeliverForChannel dynamically starts delivery of new blocks from ordering service
 	// to channel peers.
-	StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo) error
+	// When the delivery finishes, the finalizer func is called
+	StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo, finalizer func()) error
 
 	// StopDeliverForChannel dynamically stops delivery of new blocks from ordering service
 	// to channel peers.
@@ -117,7 +125,7 @@ func (d *deliverServiceImpl) validateConfiguration() error {
 // initializes the grpc stream for given chainID, creates blocks provider instance
 // that spawns in go routine to read new blocks starting from the position provided by ledger
 // info instance.
-func (d *deliverServiceImpl) StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo) error {
+func (d *deliverServiceImpl) StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo, finalizer func()) error {
 	d.lock.Lock()
 	defer d.lock.Unlock()
 	if d.stopping {
@@ -133,7 +141,10 @@ func (d *deliverServiceImpl) StartDeliverForChannel(chainID string, ledgerInfo b
 		client := d.newClient(chainID, ledgerInfo)
 		logger.Debug("This peer will pass blocks from orderer service to other peers for channel", chainID)
 		d.blockProviders[chainID] = blocksprovider.NewBlocksProvider(chainID, client, d.conf.Gossip, d.conf.CryptoSvc)
-		go d.blockProviders[chainID].DeliverBlocks()
+		go func() {
+			d.blockProviders[chainID].DeliverBlocks()
+			finalizer()
+		}()
 	}
 	return nil
 }

core/deliverservice/deliveryclient_test.go

@@ -113,10 +113,10 @@ func TestNewDeliverService(t *testing.T) {
 		ConnFactory: connFactory,
 	})
 	assert.NoError(t, err)
-	assert.NoError(t, service.StartDeliverForChannel("TEST_CHAINID", &mocks.MockLedgerInfo{0}))
+	assert.NoError(t, service.StartDeliverForChannel("TEST_CHAINID", &mocks.MockLedgerInfo{0}, func() {}))
 
 	// Lets start deliver twice
-	assert.Error(t, service.StartDeliverForChannel("TEST_CHAINID", &mocks.MockLedgerInfo{0}), "can't start delivery")
+	assert.Error(t, service.StartDeliverForChannel("TEST_CHAINID", &mocks.MockLedgerInfo{0}, func() {}), "can't start delivery")
 	// Lets stop deliver that not started
 	assert.Error(t, service.StopDeliverForChannel("TEST_CHAINID2"), "can't stop delivery")
 
@@ -130,7 +130,7 @@ func TestNewDeliverService(t *testing.T) {
 	assert.Equal(t, 0, connNumber)
 	assertBlockDissemination(0, gossipServiceAdapter.GossipBlockDisseminations, t)
 	assert.Equal(t, atomic.LoadInt32(&blocksDeliverer.RecvCnt), atomic.LoadInt32(&gossipServiceAdapter.AddPayloadsCnt))
-	assert.Error(t, service.StartDeliverForChannel("TEST_CHAINID", &mocks.MockLedgerInfo{0}), "Delivery service is stopping")
+	assert.Error(t, service.StartDeliverForChannel("TEST_CHAINID", &mocks.MockLedgerInfo{0}, func() {}), "Delivery service is stopping")
 	assert.Error(t, service.StopDeliverForChannel("TEST_CHAINID"), "Delivery service is stopping")
 }
 
@@ -157,7 +157,7 @@ func TestDeliverServiceRestart(t *testing.T) {
 	li := &mocks.MockLedgerInfo{Height: uint64(100)}
 	os.SetNextExpectedSeek(uint64(100))
 
-	err = service.StartDeliverForChannel("TEST_CHAINID", li)
+	err = service.StartDeliverForChannel("TEST_CHAINID", li, func() {})
 	assert.NoError(t, err, "can't start delivery")
 	// Check that delivery client requests blocks in order
 	go os.SendBlock(uint64(100))
@@ -203,7 +203,7 @@ func TestDeliverServiceFailover(t *testing.T) {
 	os1.SetNextExpectedSeek(uint64(100))
 	os2.SetNextExpectedSeek(uint64(100))
 
-	err = service.StartDeliverForChannel("TEST_CHAINID", li)
+	err = service.StartDeliverForChannel("TEST_CHAINID", li, func() {})
 	assert.NoError(t, err, "can't start delivery")
 	// We need to discover to which instance the client connected to
 	go os1.SendBlock(uint64(100))
@@ -278,7 +278,7 @@ func TestDeliverServiceServiceUnavailable(t *testing.T) {
 	os1.SetNextExpectedSeek(li.Height)
 	os2.SetNextExpectedSeek(li.Height)
 
-	err = service.StartDeliverForChannel("TEST_CHAINID", li)
+	err = service.StartDeliverForChannel("TEST_CHAINID", li, func() {})
 	assert.NoError(t, err, "can't start delivery")
 
 	waitForConnectionToSomeOSN := func() (*mocks.Orderer, *mocks.Orderer) {
@@ -367,7 +367,7 @@ func TestDeliverServiceShutdown(t *testing.T) {
 
 	li := &mocks.MockLedgerInfo{Height: uint64(100)}
 	os.SetNextExpectedSeek(uint64(100))
-	err = service.StartDeliverForChannel("TEST_CHAINID", li)
+	err = service.StartDeliverForChannel("TEST_CHAINID", li, func() {})
 	assert.NoError(t, err, "can't start delivery")
 
 	// Check that delivery service requests blocks in order

core/peer/peer_test.go

@@ -48,7 +48,7 @@ type mockDeliveryClient struct {
 
 // StartDeliverForChannel dynamically starts delivery of new blocks from ordering service
 // to channel peers.
-func (ds *mockDeliveryClient) StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo) error {
+func (ds *mockDeliveryClient) StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo, f func()) error {
 	return nil
 }
 

core/scc/cscc/configure_test.go

@@ -55,7 +55,7 @@ type mockDeliveryClient struct {
 
 // StartDeliverForChannel dynamically starts delivery of new blocks from ordering service
 // to channel peers.
-func (ds *mockDeliveryClient) StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo) error {
+func (ds *mockDeliveryClient) StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo, f func()) error {
 	return nil
 }
 

gossip/election/election.go

@@ -93,6 +93,10 @@ type LeaderElectionService interface {
 
 	// Stop stops the LeaderElectionService
 	Stop()
+
+	// Yield relinquishes the leadership until a new leader is elected,
+	// or a timeout expires
+	Yield()
 }
 
 type peerID []byte
@@ -150,10 +154,12 @@ type leaderElectionSvcImpl struct {
 	isLeader      int32
 	toDie         int32
 	leaderExists  int32
+	yield         int32
 	sleeping      bool
 	adapter       LeaderElectionAdapter
 	logger        *logging.Logger
 	callback      leadershipCallback
+	yieldTimer    *time.Timer
 }
 
 func (le *leaderElectionSvcImpl) start() {
@@ -239,6 +245,11 @@ func (le *leaderElectionSvcImpl) run() {
 		if !le.isLeaderExists() {
 			le.leaderElection()
 		}
+		// If we are yielding and some leader has been elected,
+		// stop yielding
+		if le.isLeaderExists() && le.isYielding() {
+			le.stopYielding()
+		}
 		if le.shouldStop() {
 			return
 		}
@@ -253,14 +264,26 @@ func (le *leaderElectionSvcImpl) run() {
 func (le *leaderElectionSvcImpl) leaderElection() {
 	le.logger.Debug(le.id, ": Entering")
 	defer le.logger.Debug(le.id, ": Exiting")
+	// If we're yielding to other peers, do not participate
+	// in leader election
+	if le.isYielding() {
+		return
+	}
+	// Propose ourselves as a leader
 	le.propose()
+	// Collect other proposals
 	le.waitForInterrupt(getLeaderElectionDuration())
 	// If someone declared itself as a leader, give up
 	// on trying to become a leader too
 	if le.isLeaderExists() {
 		le.logger.Debug(le.id, ": Some peer is already a leader")
 		return
 	}
+
+	if le.isYielding() {
+		le.logger.Debug(le.id, ": Aborting leader election because yielding")
+		return
+	}
 	// Leader doesn't exist, let's see if there is a better candidate than us
 	// for being a leader
 	for _, o := range le.proposals.ToArray() {
@@ -364,6 +387,38 @@ func (le *leaderElectionSvcImpl) shouldStop() bool {
 	return atomic.LoadInt32(&le.toDie) == int32(1)
 }
 
+func (le *leaderElectionSvcImpl) isYielding() bool {
+	return atomic.LoadInt32(&le.yield) == int32(1)
+}
+
+func (le *leaderElectionSvcImpl) stopYielding() {
+	le.logger.Debug("Stopped yielding")
+	le.Lock()
+	defer le.Unlock()
+	atomic.StoreInt32(&le.yield, int32(0))
+	le.yieldTimer.Stop()
+}
+
+// Yield relinquishes the leadership until a new leader is elected,
+// or a timeout expires
+func (le *leaderElectionSvcImpl) Yield() {
+	le.Lock()
+	defer le.Unlock()
+	if !le.IsLeader() || le.isYielding() {
+		return
+	}
+	// Turn on the yield flag
+	atomic.StoreInt32(&le.yield, int32(1))
+	// Stop being a leader
+	le.stopBeingLeader()
+	// Clear the leader exists flag since it could be that we are the leader
+	atomic.StoreInt32(&le.leaderExists, int32(0))
+	// Clear the yield flag in any case afterwards
+	le.yieldTimer = time.AfterFunc(getLeaderAliveThreshold()*6, func() {
+		atomic.StoreInt32(&le.yield, int32(0))
+	})
+}
+
 // Stop stops the LeaderElectionService
 func (le *leaderElectionSvcImpl) Stop() {
 	le.logger.Debug(le.id, ": Entering")

gossip/election/election_test.go

@@ -308,6 +308,70 @@ func TestLeadershipTakeover(t *testing.T) {
 	assert.Equal(t, "p2", leaders[0])
 }
 
+func TestYield(t *testing.T) {
+	t.Parallel()
+	// Scenario: Peers spawn and a leader is elected.
+	// After a while, the leader yields.
+	// (Call yield twice to ensure only one callback is called)
+	// Expected outcome:
+	// (1) A new leader is elected
+	// (2) The old leader doesn't take back its leadership
+	peers := createPeers(0, 0, 1, 2, 3, 4, 5)
+	leaders := waitForLeaderElection(t, peers)
+	assert.Len(t, leaders, 1, "Only 1 leader should have been elected")
+	assert.Equal(t, "p0", leaders[0])
+	peers[0].Yield()
+	// Ensure the callback was called with 'false'
+	assert.True(t, peers[0].isCallbackInvoked())
+	assert.False(t, peers[0].isLeaderFromCallback())
+	// Clear the callback invoked flag
+	peers[0].lock.Lock()
+	peers[0].callbackInvoked = false
+	peers[0].lock.Unlock()
+	// Yield again and ensure it isn't called again
+	peers[0].Yield()
+	assert.False(t, peers[0].isCallbackInvoked())
+
+	ensureP0isNotAleader := func() bool {
+		leaders := waitForLeaderElection(t, peers)
+		return len(leaders) == 1 && leaders[0] != "p0"
+	}
+	// A new leader is elected, and it is not p0
+	waitForBoolFunc(t, ensureP0isNotAleader, true)
+	time.Sleep(getLeaderAliveThreshold() * 2)
+	// After a while, p0 doesn't restore its leadership status
+	waitForBoolFunc(t, ensureP0isNotAleader, true)
+}
+
+func TestYieldSinglePeer(t *testing.T) {
+	t.Parallel()
+	// Scenario: spawn a single peer and have it yield.
+	// Ensure it recovers its leadership after a while.
+	peers := createPeers(0, 0)
+	waitForLeaderElection(t, peers)
+	peers[0].Yield()
+	assert.False(t, peers[0].IsLeader())
+	waitForLeaderElection(t, peers)
+}
+
+func TestYieldAllPeers(t *testing.T) {
+	t.Parallel()
+	// Scenario: spawn 2 peers and have them all yield after regaining leadership.
+	// Ensure the first peer is the leader in the end after both peers yield
+	peers := createPeers(0, 0, 1)
+	leaders := waitForLeaderElection(t, peers)
+	assert.Len(t, leaders, 1, "Only 1 leader should have been elected")
+	assert.Equal(t, "p0", leaders[0])
+	peers[0].Yield()
+	leaders = waitForLeaderElection(t, peers)
+	assert.Len(t, leaders, 1, "Only 1 leader should have been elected")
+	assert.Equal(t, "p1", leaders[0])
+	peers[1].Yield()
+	leaders = waitForLeaderElection(t, peers)
+	assert.Len(t, leaders, 1, "Only 1 leader should have been elected")
+	assert.Equal(t, "p0", leaders[0])
+}
+
 func TestPartition(t *testing.T) {
 	t.Parallel()
 	// Scenario: peers spawn together, and then after a while a network partition occurs

gossip/service/gossip_service.go

@@ -196,7 +196,7 @@ func (g *gossipServiceImpl) InitializeChannel(chainID string, committer committe
 			g.leaderElection[chainID] = g.newLeaderElectionComponent(chainID, g.onStatusChangeFactory(chainID, committer))
 		} else if isStaticOrgLeader {
 			logger.Debug("This peer is configured to connect to ordering service for blocks delivery, channel", chainID)
-			g.deliveryService.StartDeliverForChannel(chainID, committer)
+			g.deliveryService.StartDeliverForChannel(chainID, committer, func() {})
 		} else {
 			logger.Debug("This peer is not configured to connect to ordering service for blocks delivery, channel", chainID)
 		}
@@ -282,8 +282,12 @@ func (g *gossipServiceImpl) amIinChannel(myOrg string, config Config) bool {
 func (g *gossipServiceImpl) onStatusChangeFactory(chainID string, committer blocksprovider.LedgerInfo) func(bool) {
 	return func(isLeader bool) {
 		if isLeader {
+			yield := func() {
+				le := g.leaderElection[chainID]
+				le.Yield()
+			}
 			logger.Info("Elected as a leader, starting delivery service for channel", chainID)
-			if err := g.deliveryService.StartDeliverForChannel(chainID, committer); err != nil {
+			if err := g.deliveryService.StartDeliverForChannel(chainID, committer, yield); err != nil {
 				logger.Error("Delivery service is not able to start blocks delivery for chain, due to", err)
 			}
 		} else {

gossip/service/gossip_service_test.go

@@ -276,7 +276,7 @@ type mockDeliverService struct {
 	running map[string]bool
 }
 
-func (ds *mockDeliverService) StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo) error {
+func (ds *mockDeliverService) StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo, finalizer func()) error {
 	ds.running[chainID] = true
 	return nil
 }