func (ls *Stores) updateBootstrapInfo(bi *gossip.BootstrapInfo) error {
	if bi.Timestamp.Less(ls.biLatestTS) {
		return nil
	}
	// Update the latest timestamp and set cached version.
	ls.biLatestTS = bi.Timestamp
	ls.latestBI = protoutil.Clone(bi).(*gossip.BootstrapInfo)
	// Update all stores.
	for _, s := range ls.storeMap {
		if err := engine.MVCCPutProto(context.Background(), s.engine, nil, keys.StoreGossipKey(), hlc.ZeroTimestamp, nil, bi); err != nil {
			return err
		}
	}
	return nil
}

// loadState loads a ReplicaState from disk. The exception is the Desc field,
// which is updated transactionally, and is populated from the supplied
// RangeDescriptor under the convention that that is the latest committed
// version.
func loadState(
	ctx context.Context,
	reader engine.Reader, desc *roachpb.RangeDescriptor,
) (storagebase.ReplicaState, error) {
	var s storagebase.ReplicaState
	// TODO(tschottdorf): figure out whether this is always synchronous with
	// on-disk state (likely iffy during Split/ChangeReplica triggers).
	s.Desc = protoutil.Clone(desc).(*roachpb.RangeDescriptor)
	// Read the range lease.
	var err error
	if s.Lease, err = loadLease(ctx, reader, desc.RangeID); err != nil {
		return storagebase.ReplicaState{}, err
	}

	if s.Frozen, err = loadFrozenStatus(ctx, reader, desc.RangeID); err != nil {
		return storagebase.ReplicaState{}, err
	}

	if s.GCThreshold, err = loadGCThreshold(ctx, reader, desc.RangeID); err != nil {
		return storagebase.ReplicaState{}, err
	}

	if s.RaftAppliedIndex, s.LeaseAppliedIndex, err = loadAppliedIndex(
		ctx, reader, desc.RangeID,
	); err != nil {
		return storagebase.ReplicaState{}, err
	}

	if s.Stats, err = loadMVCCStats(ctx, reader, desc.RangeID); err != nil {
		return storagebase.ReplicaState{}, err
	}

	// The truncated state should not be optional (i.e. the pointer is
	// pointless), but it is and the migration is not worth it.
	truncState, err := loadTruncatedState(ctx, reader, desc.RangeID)
	if err != nil {
		return storagebase.ReplicaState{}, err
	}
	s.TruncatedState = &truncState

	return s, nil
}

func TestCloneProto(t *testing.T) {
	testCases := []struct {
		pb          proto.Message
		shouldPanic bool
	}{
		{&roachpb.StoreIdent{}, false},
		{&roachpb.StoreIdent{ClusterID: uuid.MakeV4()}, true},
		{&roachpb.TxnMeta{}, false},
		{&roachpb.TxnMeta{ID: uuid.NewV4()}, true},
		{&roachpb.Transaction{}, false},
		{&config.ZoneConfig{RangeMinBytes: 123, RangeMaxBytes: 456}, false},
	}
	for _, tc := range testCases {
		var clone proto.Message
		var panicObj interface{}
		func() {
			defer func() {
				panicObj = recover()
			}()
			clone = protoutil.Clone(tc.pb)
		}()

		if tc.shouldPanic {
			if panicObj == nil {
				t.Errorf("%T: expected panic but didn't get one", tc.pb)
			}
		} else {
			if panicObj != nil {
				if panicStr := fmt.Sprint(panicObj); !strings.Contains(panicStr, "attempt to clone") {
					t.Errorf("%T: got unexpected panic %s", tc.pb, panicStr)
				}
			}
		}

		if panicObj == nil {
			realClone := proto.Clone(tc.pb)
			if !reflect.DeepEqual(clone, realClone) {
				t.Errorf("%T: clone did not equal original. expected:\n%+v\ngot:\n%+v", tc.pb, realClone, clone)
			}
		}
	}
}

// Send implements the batch.Sender interface. If the request is part of a
// transaction, the TxnCoordSender adds the transaction to a map of active
// transactions and begins heartbeating it. Every subsequent request for the
// same transaction updates the lastUpdate timestamp to prevent live
// transactions from being considered abandoned and garbage collected.
// Read/write mutating requests have their key or key range added to the
// transaction's interval tree of key ranges for eventual cleanup via resolved
// write intents; they're tagged to an outgoing EndTransaction request, with
// the receiving replica in charge of resolving them.
func (tc *TxnCoordSender) Send(ctx context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	{
		// Start new or pick up active trace and embed its trace metadata into
		// header for use by RPC recipients. From here on, there's always an active
		// Trace, though its overhead is small unless it's sampled.
		sp := opentracing.SpanFromContext(ctx)
		// TODO(radu): once contexts are plumbed correctly, we should use the Tracer
		// from ctx.
		tracer := tracing.TracerFromCtx(tc.ctx)
		if sp == nil {
			sp = tracer.StartSpan(opTxnCoordSender)
			defer sp.Finish()
			ctx = opentracing.ContextWithSpan(ctx, sp)
		}
		// TODO(tschottdorf): To get rid of the spurious alloc below we need to
		// implement the carrier interface on ba.Header or make Span non-nullable,
		// both of which force all of ba on the Heap. It's already there, so may
		// not be a big deal, but ba should live on the stack. Also not easy to use
		// a buffer pool here since anything that goes into the RPC layer could be
		// used by goroutines we didn't wait for.
		if ba.Header.Trace == nil {
			ba.Header.Trace = &tracing.Span{}
		} else {
			// We didn't make this object but are about to mutate it, so we
			// have to take a copy - the original might already have been
			// passed to the RPC layer.
			ba.Header.Trace = protoutil.Clone(ba.Header.Trace).(*tracing.Span)
		}
		if err := tracer.Inject(sp.Context(), basictracer.Delegator, ba.Trace); err != nil {
			return nil, roachpb.NewError(err)
		}
	}

	startNS := tc.clock.PhysicalNow()

	if ba.Txn != nil {
		// If this request is part of a transaction...
		if err := tc.maybeBeginTxn(&ba); err != nil {
			return nil, roachpb.NewError(err)
		}
		var et *roachpb.EndTransactionRequest
		var hasET bool
		{
			var rArgs roachpb.Request
			rArgs, hasET = ba.GetArg(roachpb.EndTransaction)
			if hasET {
				et = rArgs.(*roachpb.EndTransactionRequest)
				if len(et.Key) != 0 {
					return nil, roachpb.NewErrorf("EndTransaction must not have a Key set")
				}
				et.Key = ba.Txn.Key
				if len(et.IntentSpans) > 0 {
					// TODO(tschottdorf): it may be useful to allow this later.
					// That would be part of a possible plan to allow txns which
					// write on multiple coordinators.
					return nil, roachpb.NewErrorf("client must not pass intents to EndTransaction")
				}
			}
		}

		if pErr := func() *roachpb.Error {
			tc.Lock()
			defer tc.Unlock()
			if pErr := tc.maybeRejectClientLocked(ctx, *ba.Txn); pErr != nil {
				return pErr
			}

			if !hasET {
				return nil
			}
			// Everything below is carried out only when trying to commit.

			// Populate et.IntentSpans, taking into account both any existing
			// and new writes, and taking care to perform proper deduplication.
			txnMeta := tc.txns[*ba.Txn.ID]
			distinctSpans := true
			if txnMeta != nil {
				et.IntentSpans = txnMeta.keys
				// Defensively set distinctSpans to false if we had any previous
				// requests in this transaction. This effectively limits the distinct
				// spans optimization to 1pc transactions.
				distinctSpans = len(txnMeta.keys) == 0
			}
			ba.IntentSpanIterate(func(key, endKey roachpb.Key) {
				et.IntentSpans = append(et.IntentSpans, roachpb.Span{
					Key:    key,
					EndKey: endKey,
				})
			})
			// TODO(peter): Populate DistinctSpans on all batches, not just batches
			// which contain an EndTransactionRequest.
//.........这里部分代码省略.........

//.........这里部分代码省略.........
) <-chan *roachpb.Error {
	if nextLease := p.RequestPending(); nextLease != nil {
		if nextLease.Replica.ReplicaID == nextLeaseHolder.ReplicaID {
			// Join a pending request asking for the same replica to become lease
			// holder.
			return p.JoinRequest()
		}
		llChan := make(chan *roachpb.Error, 1)
		// We can't join the request in progress.
		llChan <- roachpb.NewErrorf("request for different replica in progress "+
			"(requesting: %+v, in progress: %+v)",
			nextLeaseHolder.ReplicaID, nextLease.Replica.ReplicaID)
		return llChan
	}
	llChan := make(chan *roachpb.Error, 1)
	// No request in progress. Let's propose a Lease command asynchronously.
	// TODO(tschottdorf): get duration from configuration, either as a
	// config flag or, later, dynamically adjusted.
	startStasis := timestamp.Add(int64(replica.store.ctx.rangeLeaseActiveDuration), 0)
	expiration := startStasis.Add(int64(replica.store.Clock().MaxOffset()), 0)
	reqSpan := roachpb.Span{
		Key: startKey,
	}
	var leaseReq roachpb.Request
	reqLease := roachpb.Lease{
		Start:       timestamp,
		StartStasis: startStasis,
		Expiration:  expiration,
		Replica:     nextLeaseHolder,
	}
	if transfer {
		leaseReq = &roachpb.TransferLeaseRequest{
			Span:  reqSpan,
			Lease: reqLease,
		}
	} else {
		leaseReq = &roachpb.RequestLeaseRequest{
			Span:  reqSpan,
			Lease: reqLease,
		}
	}
	if replica.store.Stopper().RunAsyncTask(func() {
		// Propose a RequestLease command and wait for it to apply.
		var execPErr *roachpb.Error
		ba := roachpb.BatchRequest{}
		ba.Timestamp = replica.store.Clock().Now()
		ba.RangeID = replica.RangeID
		ba.Add(leaseReq)
		// Send lease request directly to raft in order to skip unnecessary
		// checks from normal request machinery, (e.g. the command queue).
		// Note that the command itself isn't traced, but usually the caller
		// waiting for the result has an active Trace.
		ch, _, err := replica.proposeRaftCommand(
			replica.context(context.Background()), ba)
		if err != nil {
			execPErr = roachpb.NewError(err)
		} else {
			// If the command was committed, wait for the range to apply it.
			select {
			case c := <-ch:
				if c.Err != nil {
					if log.V(1) {
						log.Infof("failed to acquire lease for replica %s: %s", replica.store, c.Err)
					}
					execPErr = c.Err
				}
			case <-replica.store.Stopper().ShouldQuiesce():
				execPErr = roachpb.NewError(
					replica.newNotLeaseHolderError(nil, replica.store.StoreID(), replica.Desc()))
			}
		}

		// Send result of lease to all waiter channels.
		replica.mu.Lock()
		defer replica.mu.Unlock()
		for i, llChan := range p.llChans {
			// Don't send the same pErr object twice; this can lead to races. We could
			// clone every time but it's more efficient to send pErr itself to one of
			// the channels (the last one; if we send it earlier the race can still
			// happen).
			if i == len(p.llChans)-1 {
				llChan <- execPErr
			} else {
				llChan <- protoutil.Clone(execPErr).(*roachpb.Error) // works with `nil`
			}
		}
		p.llChans = p.llChans[:0]
		p.nextLease = roachpb.Lease{}
	}) != nil {
		// We failed to start the asynchronous task. Send a blank NotLeaseHolderError
		// back to indicate that we have no idea who the range lease holder might
		// be; we've withdrawn from active duty.
		llChan <- roachpb.NewError(
			replica.newNotLeaseHolderError(nil, replica.store.StoreID(), replica.mu.state.Desc))
		return llChan
	}
	p.llChans = append(p.llChans, llChan)
	p.nextLease = reqLease
	return llChan
}

//.........这里部分代码省略.........
	}
	isDone, err = changer.IsDone()
	if err != nil {
		t.Fatal(err)
	}
	if isDone {
		t.Fatalf("table expected to have an outstanding schema change: %v", desc.GetTable())
	}
	desc, err = changer.MaybeIncrementVersion()
	if err != nil {
		t.Fatal(err)
	}
	tableDesc = desc.GetTable()
	savedTableDesc := sqlbase.GetTableDescriptor(kvDB, "t", "test")
	newVersion = tableDesc.Version
	if newVersion != expectedVersion {
		t.Fatalf("bad version in returned desc; e = %d, v = %d", expectedVersion, newVersion)
	}
	newVersion = savedTableDesc.Version
	if newVersion != expectedVersion {
		t.Fatalf("bad version in saved desc; e = %d, v = %d", expectedVersion, newVersion)
	}
	isDone, err = changer.IsDone()
	if err != nil {
		t.Fatal(err)
	}
	if !isDone {
		t.Fatalf("table expected to not have an outstanding schema change: %v", tableDesc)
	}

	// Check that RunStateMachineBeforeBackfill doesn't do anything
	// if there are no mutations queued.
	if err := changer.RunStateMachineBeforeBackfill(); err != nil {
		t.Fatal(err)
	}

	tableDesc = sqlbase.GetTableDescriptor(kvDB, "t", "test")
	newVersion = tableDesc.Version
	if newVersion != expectedVersion {
		t.Fatalf("bad version; e = %d, v = %d", expectedVersion, newVersion)
	}

	// Check that RunStateMachineBeforeBackfill functions properly.
	expectedVersion = tableDesc.Version
	// Make a copy of the index for use in a mutation.
	index := protoutil.Clone(&tableDesc.Indexes[0]).(*sqlbase.IndexDescriptor)
	index.Name = "bar"
	index.ID = tableDesc.NextIndexID
	tableDesc.NextIndexID++
	changer = csql.NewSchemaChangerForTesting(id, tableDesc.NextMutationID, node, *kvDB, leaseMgr)
	tableDesc.Mutations = append(tableDesc.Mutations, sqlbase.DescriptorMutation{
		Descriptor_: &sqlbase.DescriptorMutation_Index{Index: index},
		Direction:   sqlbase.DescriptorMutation_ADD,
		State:       sqlbase.DescriptorMutation_DELETE_ONLY,
		MutationID:  tableDesc.NextMutationID,
	})
	tableDesc.NextMutationID++

	// Run state machine in both directions.
	for _, direction := range []sqlbase.DescriptorMutation_Direction{sqlbase.DescriptorMutation_ADD, sqlbase.DescriptorMutation_DROP} {
		tableDesc.Mutations[0].Direction = direction
		expectedVersion++
		if err := kvDB.Put(
			sqlbase.MakeDescMetadataKey(tableDesc.ID),
			sqlbase.WrapDescriptor(tableDesc),
		); err != nil {
			t.Fatal(err)
		}
		// The expected end state.
		expectedState := sqlbase.DescriptorMutation_WRITE_ONLY
		if direction == sqlbase.DescriptorMutation_DROP {
			expectedState = sqlbase.DescriptorMutation_DELETE_ONLY
		}
		// Run two times to ensure idempotency of operations.
		for i := 0; i < 2; i++ {
			if err := changer.RunStateMachineBeforeBackfill(); err != nil {
				t.Fatal(err)
			}

			tableDesc = sqlbase.GetTableDescriptor(kvDB, "t", "test")
			newVersion = tableDesc.Version
			if newVersion != expectedVersion {
				t.Fatalf("bad version; e = %d, v = %d", expectedVersion, newVersion)
			}
			state := tableDesc.Mutations[0].State
			if state != expectedState {
				t.Fatalf("bad state; e = %d, v = %d", expectedState, state)
			}
		}
	}
	// RunStateMachineBeforeBackfill() doesn't complete the schema change.
	isDone, err = changer.IsDone()
	if err != nil {
		t.Fatal(err)
	}
	if isDone {
		t.Fatalf("table expected to have an outstanding schema change: %v", tableDesc)
	}

}

// TestStoreRangeSplitRaceUninitializedRHS reproduces #7600 (before it was
// fixed). While splits are happening, we simulate incoming messages for the
// right-hand side to trigger a race between the creation of the proper replica
// and the uninitialized replica reacting to messages.
func TestStoreRangeSplitRaceUninitializedRHS(t *testing.T) {
	defer leaktest.AfterTest(t)()
	mtc := &multiTestContext{}
	storeCtx := storage.TestStoreContext()
	// An aggressive tick interval lets groups communicate more and thus
	// triggers test failures much more reliably. We can't go too aggressive
	// or race tests never make any progress.
	storeCtx.RaftTickInterval = 50 * time.Millisecond
	storeCtx.RaftElectionTimeoutTicks = 2
	currentTrigger := make(chan *roachpb.SplitTrigger)
	seen := make(map[storagebase.CmdIDKey]struct{})
	storeCtx.TestingKnobs.TestingCommandFilter = func(args storagebase.FilterArgs) *roachpb.Error {
		et, ok := args.Req.(*roachpb.EndTransactionRequest)
		if !ok || et.InternalCommitTrigger == nil {
			return nil
		}
		trigger := protoutil.Clone(et.InternalCommitTrigger.GetSplitTrigger()).(*roachpb.SplitTrigger)
		if trigger != nil && len(trigger.NewDesc.Replicas) == 2 && args.Hdr.Txn.Epoch == 0 && args.Sid == mtc.stores[0].StoreID() {
			if _, ok := seen[args.CmdID]; ok {
				return nil
			}
			// Without replay protection, a single reproposal locks up the
			// test.
			seen[args.CmdID] = struct{}{}
			currentTrigger <- trigger
			return roachpb.NewError(roachpb.NewReadWithinUncertaintyIntervalError(args.Hdr.Timestamp, args.Hdr.Timestamp))
		}
		return nil
	}

	mtc.storeContext = &storeCtx
	mtc.Start(t, 2)
	defer mtc.Stop()

	leftRange := mtc.stores[0].LookupReplica(roachpb.RKey("a"), nil)

	// We'll fake messages from term 1, ..., .magicIters-1. The exact number
	// doesn't matter for anything but for its likelihood of triggering the
	// race.
	const magicIters = 5

	// Replicate the left range onto the second node. We don't wait since we
	// don't actually care what the second node does. All we want is that the
	// first node isn't surprised by messages from that node.
	mtc.replicateRange(leftRange.RangeID, 1)

	for i := 0; i < 10; i++ {
		var wg sync.WaitGroup
		wg.Add(2)

		go func() {
			defer wg.Done()
			// Split the data range. The split keys are chosen so that they move
			// towards "a" (so that the range being split is always the first
			// range).
			splitKey := roachpb.Key(encoding.EncodeVarintDescending([]byte("a"), int64(i)))
			splitArgs := adminSplitArgs(keys.SystemMax, splitKey)
			if _, pErr := client.SendWrapped(mtc.distSenders[0], nil, &splitArgs); pErr != nil {
				t.Fatal(pErr)
			}
		}()
		go func() {
			defer wg.Done()

			trigger := <-currentTrigger // our own copy
			// Make sure the first node is first for convenience.
			replicas := trigger.NewDesc.Replicas
			if replicas[0].NodeID > replicas[1].NodeID {
				tmp := replicas[1]
				replicas[1] = replicas[0]
				replicas[0] = tmp
			}

			// Send a few vote requests which look like they're from the other
			// node's right hand side of the split. This triggers a race which
			// is discussed in #7600 (briefly, the creation of the right hand
			// side in the split trigger was racing with the uninitialized
			// version for the same group, resulting in clobbered HardState).
			for term := uint64(1); term < magicIters; term++ {
				if err := mtc.stores[0].HandleRaftMessage(&storage.RaftMessageRequest{
					RangeID:     trigger.NewDesc.RangeID,
					ToReplica:   replicas[0],
					FromReplica: replicas[1],
					Message: raftpb.Message{
						Type: raftpb.MsgVote,
						To:   uint64(replicas[0].ReplicaID),
						From: uint64(replicas[1].ReplicaID),
						Term: term,
					},
				}); err != nil {
					t.Error(err)
				}
			}
		}()
		wg.Wait()
	}
//.........这里部分代码省略.........

//.........这里部分代码省略.........
		t.Fatalf("table expected to have an outstanding schema change: %v", desc.GetTable())
	}
	desc, err = changer.MaybeIncrementVersion()
	if err != nil {
		t.Fatal(err)
	}
	savedDesc := &sqlbase.Descriptor{}
	if err := kvDB.GetProto(descKey, savedDesc); err != nil {
		t.Fatal(err)
	}
	newVersion = desc.GetTable().Version
	if newVersion != expectedVersion {
		t.Fatalf("bad version in returned desc; e = %d, v = %d", expectedVersion, newVersion)
	}
	newVersion = savedDesc.GetTable().Version
	if newVersion != expectedVersion {
		t.Fatalf("bad version in saved desc; e = %d, v = %d", expectedVersion, newVersion)
	}
	isDone, err = changer.IsDone()
	if err != nil {
		t.Fatal(err)
	}
	if !isDone {
		t.Fatalf("table expected to not have an outstanding schema change: %v", desc.GetTable())
	}

	// Check that RunStateMachineBeforeBackfill doesn't do anything
	// if there are no mutations queued.
	if err := changer.RunStateMachineBeforeBackfill(); err != nil {
		t.Fatal(err)
	}
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}
	newVersion = desc.GetTable().Version
	if newVersion != expectedVersion {
		t.Fatalf("bad version; e = %d, v = %d", expectedVersion, newVersion)
	}

	// Check that RunStateMachineBeforeBackfill functions properly.
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}
	table := desc.GetTable()
	expectedVersion = table.Version
	// Make a copy of the index for use in a mutation.
	index := protoutil.Clone(&table.Indexes[0]).(*sqlbase.IndexDescriptor)
	index.Name = "bar"
	index.ID = table.NextIndexID
	table.NextIndexID++
	changer = csql.NewSchemaChangerForTesting(id, table.NextMutationID, node, *db, leaseMgr)
	table.Mutations = append(table.Mutations, sqlbase.DescriptorMutation{
		Descriptor_: &sqlbase.DescriptorMutation_Index{Index: index},
		Direction:   sqlbase.DescriptorMutation_ADD,
		State:       sqlbase.DescriptorMutation_DELETE_ONLY,
		MutationID:  table.NextMutationID,
	})
	table.NextMutationID++

	// Run state machine in both directions.
	for _, direction := range []sqlbase.DescriptorMutation_Direction{sqlbase.DescriptorMutation_ADD, sqlbase.DescriptorMutation_DROP} {
		table.Mutations[0].Direction = direction
		expectedVersion++
		if err := kvDB.Put(descKey, desc); err != nil {
			t.Fatal(err)
		}
		// The expected end state.
		expectedState := sqlbase.DescriptorMutation_WRITE_ONLY
		if direction == sqlbase.DescriptorMutation_DROP {
			expectedState = sqlbase.DescriptorMutation_DELETE_ONLY
		}
		// Run two times to ensure idempotency of operations.
		for i := 0; i < 2; i++ {
			if err := changer.RunStateMachineBeforeBackfill(); err != nil {
				t.Fatal(err)
			}
			if err := kvDB.GetProto(descKey, desc); err != nil {
				t.Fatal(err)
			}
			table = desc.GetTable()
			newVersion = table.Version
			if newVersion != expectedVersion {
				t.Fatalf("bad version; e = %d, v = %d", expectedVersion, newVersion)
			}
			state := table.Mutations[0].State
			if state != expectedState {
				t.Fatalf("bad state; e = %d, v = %d", expectedState, state)
			}
		}
	}
	// RunStateMachineBeforeBackfill() doesn't complete the schema change.
	isDone, err = changer.IsDone()
	if err != nil {
		t.Fatal(err)
	}
	if isDone {
		t.Fatalf("table expected to have an outstanding schema change: %v", desc.GetTable())
	}

}