Golang gossiputil.NewStoreGossiper函数代码示例

func TestRebalanceInterval(t *testing.T) {
	defer leaktest.AfterTest(t)()

	if defaultMinRebalanceInterval <= gossip.DefaultGossipStoresInterval {
		t.Fatalf("defaultMinRebalanceInterval (%s) cannot be shorter than "+
			"DefaultGossipStoresInterval (%s)", defaultMaxRebalanceInterval, gossip.DefaultGossipStoresInterval)
	}

	if defaultMaxRebalanceInterval < defaultMinRebalanceInterval {
		t.Fatalf("defaultMaxRebalanceInterval (%s) < defaultMinRebalanceInterval (%s)",
			defaultMinRebalanceInterval, defaultMaxRebalanceInterval)
	}

	stopper, g, _, a, manualClock := createTestAllocator()
	defer stopper.Stop()

	stores := []*roachpb.StoreDescriptor{
		{
			StoreID:  1,
			Node:     roachpb.NodeDescriptor{NodeID: 1},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 100, RangeCount: 100},
		},
		{
			StoreID:  2,
			Node:     roachpb.NodeDescriptor{NodeID: 2},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 100, RangeCount: 1},
		},
	}
	gossiputil.NewStoreGossiper(g).GossipStores(stores, t)

	a.options.Deterministic = true
	// Store currrent time before the first rebalance decision, to avoid flakiness
	// for the nextRebalance checks below.
	now := time.Unix(0, manualClock.UnixNano())

	// The first ShouldRebalance call should always return true when there is an
	// imbalance.
	if a, e := a.ShouldRebalance(1), true; a != e {
		t.Errorf("ShouldRebalance returned %t != expected %t", a, e)
	}
	a.UpdateNextRebalance()
	backoff := a.nextRebalance.Sub(now)
	if backoff < defaultMinRebalanceInterval {
		t.Fatalf("nextRebalance interval (%s) < min (%s)", backoff, defaultMinRebalanceInterval)
	}
	if backoff > defaultMaxRebalanceInterval {
		t.Fatalf("nextRebalance interval (%s) > max (%s)", backoff, defaultMaxRebalanceInterval)
	}

	// We just rebalanced, so another rebalance should not be allowed.
	if a, e := a.ShouldRebalance(1), false; a != e {
		t.Errorf("ShouldRebalance returned %t != expected %t", a, e)
	}

	// Simulate the rebalance interval passing.
	manualClock.Increment(backoff.Nanoseconds())
	if a, e := a.ShouldRebalance(1), true; a != e {
		t.Errorf("ShouldRebalance returned %t != expected %t", a, e)
	}
}

// TestStoreRangeRemoveDead verifies that if a store becomes dead, the
// ReplicateQueue will notice and remove any replicas on it.
func TestStoreRangeRemoveDead(t *testing.T) {
	defer leaktest.AfterTest(t)
	mtc := &multiTestContext{}
	mtc.timeUntilStoreDead = storage.TestTimeUntilStoreDead
	mtc.Start(t, 3)
	defer mtc.Stop()

	sg := gossiputil.NewStoreGossiper(mtc.gossip)

	// Replicate the range to all stores.
	replica := mtc.stores[0].LookupReplica(roachpb.RKeyMin, nil)
	mtc.replicateRange(replica.Desc().RangeID, 0, 1, 2)

	// Initialize the gossip network.
	var storeIDs []roachpb.StoreID
	for _, s := range mtc.stores {
		storeIDs = append(storeIDs, s.StoreID())
	}
	sg.GossipWithFunction(storeIDs, func() {
		for _, s := range mtc.stores {
			s.GossipStore()
		}
	})

	aliveStoreIDs := []roachpb.StoreID{
		mtc.stores[0].StoreID(),
		mtc.stores[1].StoreID(),
	}

	rangeDesc := getRangeMetadata(roachpb.RKeyMin, mtc, t)
	if e, a := 3, len(rangeDesc.Replicas); e != a {
		t.Fatalf("expected %d replicas, only found %d, rangeDesc: %+v", e, a, rangeDesc)
	}

	// This can't use SucceedsWithin as using the backoff mechanic won't work
	// as it requires a specific cadence of re-gossiping the alive stores to
	// maintain their alive status.
	ticker := time.NewTicker(storage.TestTimeUntilStoreDead / 2)
	defer ticker.Stop()

	maxTime := 5 * time.Second
	maxTimeout := time.After(maxTime)

	for len(getRangeMetadata(roachpb.RKeyMin, mtc, t).Replicas) > 2 {
		select {
		case <-maxTimeout:
			t.Fatalf("Failed to remove the dead replica within %s", maxTime)
		case <-ticker.C:
			// Keep gossiping the alive stores.
			sg.GossipWithFunction(aliveStoreIDs, func() {
				mtc.stores[0].GossipStore()
				mtc.stores[1].GossipStore()
			})
			// Force the repair queues on all alive stores to run.
			mtc.stores[0].ForceReplicationScan(t)
			mtc.stores[1].ForceReplicationScan(t)
		}
	}
	ticker.Stop()
}

func TestAllocatorTwoDatacenters(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper, g, _, a, _ := createTestAllocator()
	defer stopper.Stop()
	gossiputil.NewStoreGossiper(g).GossipStores(multiDCStores, t)
	result1, err := a.AllocateTarget(multiDCConfig.ReplicaAttrs[0], []roachpb.ReplicaDescriptor{}, false, nil)
	if err != nil {
		t.Fatalf("Unable to perform allocation: %v", err)
	}
	result2, err := a.AllocateTarget(multiDCConfig.ReplicaAttrs[1], []roachpb.ReplicaDescriptor{}, false, nil)
	if err != nil {
		t.Fatalf("Unable to perform allocation: %v", err)
	}
	if result1.Node.NodeID != 1 || result2.Node.NodeID != 2 {
		t.Errorf("Expected nodes 1 & 2: %+v vs %+v", result1.Node, result2.Node)
	}
	// Verify that no result is forthcoming if we already have a replica.
	_, err = a.AllocateTarget(multiDCConfig.ReplicaAttrs[1], []roachpb.ReplicaDescriptor{
		{
			NodeID:  result2.Node.NodeID,
			StoreID: result2.StoreID,
		},
	}, false, nil)
	if err == nil {
		t.Errorf("expected error on allocation without available stores")
	}
}

// createCluster generates a new cluster using the provided stopper and the
// number of nodes supplied. Each node will have one store to start.
func createCluster(stopper *stop.Stopper, nodeCount int) *Cluster {
	rand, seed := randutil.NewPseudoRand()
	clock := hlc.NewClock(hlc.UnixNano)
	rpcContext := rpc.NewContext(&base.Context{}, clock, stopper)
	g := gossip.New(rpcContext, gossip.TestInterval, gossip.TestBootstrap)
	storePool := storage.NewStorePool(g, storage.TestTimeUntilStoreDeadOff, stopper)
	c := &Cluster{
		stopper:       stopper,
		clock:         clock,
		rpc:           rpcContext,
		gossip:        g,
		storePool:     storePool,
		allocator:     storage.MakeAllocator(storePool, storage.RebalancingOptions{}),
		storeGossiper: gossiputil.NewStoreGossiper(g),
		nodes:         make(map[proto.NodeID]*Node),
		stores:        make(map[proto.StoreID]*Store),
		ranges:        make(map[proto.RangeID]*Range),
		rand:          rand,
		seed:          seed,
	}

	// Add the nodes.
	for i := 0; i < nodeCount; i++ {
		c.addNewNodeWithStore()
	}

	// Add a single range and add to this first node's first store.
	firstRange := c.addRange()
	firstRange.attachRangeToStore(c.stores[proto.StoreID(0)])
	return c
}

// createCluster generates a new cluster using the provided stopper and the
// number of nodes supplied. Each node will have one store to start.
func createCluster(
	stopper *stop.Stopper,
	nodeCount int,
	epochWriter, actionWriter io.Writer,
	script Script,
	rand *rand.Rand,
) *Cluster {
	clock := hlc.NewClock(hlc.UnixNano)
	rpcContext := rpc.NewContext(nil, clock, stopper)
	g := gossip.New(rpcContext, nil, stopper)
	// NodeID is required for Gossip, so set it to -1 for the cluster Gossip
	// instance to prevent conflicts with real NodeIDs.
	g.SetNodeID(-1)
	storePool := storage.NewStorePool(g, clock, storage.TestTimeUntilStoreDeadOff, stopper)
	c := &Cluster{
		stopper:   stopper,
		clock:     clock,
		rpc:       rpcContext,
		gossip:    g,
		storePool: storePool,
		allocator: storage.MakeAllocator(storePool, storage.AllocatorOptions{
			AllowRebalance: true,
			Deterministic:  true,
		}),
		storeGossiper:   gossiputil.NewStoreGossiper(g),
		nodes:           make(map[roachpb.NodeID]*Node),
		stores:          make(map[roachpb.StoreID]*Store),
		ranges:          make(map[roachpb.RangeID]*Range),
		rangeIDsByStore: make(map[roachpb.StoreID]roachpb.RangeIDSlice),
		rand:            rand,
		epochWriter:     tabwriter.NewWriter(epochWriter, 8, 1, 2, ' ', 0),
		actionWriter:    tabwriter.NewWriter(actionWriter, 8, 1, 2, ' ', 0),
		script:          script,
		epoch:           -1,
	}

	// Add the nodes.
	for i := 0; i < nodeCount; i++ {
		c.addNewNodeWithStore()
	}

	// Add a single range and add to this first node's first store.
	firstRange := c.addRange()
	firstRange.addReplica(c.stores[0])

	c.calculateRangeIDsByStore()

	// Output the first epoch header.
	c.epoch = 0
	c.OutputEpochHeader()
	c.OutputEpoch()
	c.flush()

	return c
}

// TestAllocatorRebalanceByCount verifies that rebalance targets are
// chosen by range counts in the event that available capacities
// exceed the maxAvailCapacityThreshold.
func TestAllocatorRebalanceByCount(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper, g, _, a, _ := createTestAllocator()
	defer stopper.Stop()

	// Setup the stores so that only one is below the standard deviation threshold.
	stores := []*roachpb.StoreDescriptor{
		{
			StoreID:  1,
			Node:     roachpb.NodeDescriptor{NodeID: 1},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 100, RangeCount: 10},
		},
		{
			StoreID:  2,
			Node:     roachpb.NodeDescriptor{NodeID: 2},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 99, RangeCount: 10},
		},
		{
			StoreID:  3,
			Node:     roachpb.NodeDescriptor{NodeID: 3},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 98, RangeCount: 10},
		},
		{
			StoreID:  4,
			Node:     roachpb.NodeDescriptor{NodeID: 4},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 98, RangeCount: 5},
		},
	}
	gossiputil.NewStoreGossiper(g).GossipStores(stores, t)

	// Every rebalance target must be store 4 (or nil for case of missing the only option).
	for i := 0; i < 10; i++ {
		result := a.RebalanceTarget(roachpb.Attributes{},
			[]roachpb.ReplicaDescriptor{{StoreID: 1}}, 0)
		if result != nil && result.StoreID != 4 {
			t.Errorf("expected store 4; got %d", result.StoreID)
		}
	}

	// Verify shouldRebalance results.
	a.options.Deterministic = true
	for i, store := range stores {
		desc, ok := a.storePool.getStoreDescriptor(store.StoreID)
		if !ok {
			t.Fatalf("%d: unable to get store %d descriptor", i, store.StoreID)
		}
		sl, _, _ := a.storePool.getStoreList(roachpb.Attributes{}, true)
		result := a.shouldRebalance(desc, sl)
		if expResult := (i < 3); expResult != result {
			t.Errorf("%d: expected rebalance %t; got %t", i, expResult, result)
		}
	}
}

func TestAllocatorSimpleRetrieval(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper, g, _, a, _ := createTestAllocator()
	defer stopper.Stop()
	gossiputil.NewStoreGossiper(g).GossipStores(singleStore, t)
	result, err := a.AllocateTarget(simpleZoneConfig.ReplicaAttrs[0], []roachpb.ReplicaDescriptor{}, false, nil)
	if err != nil {
		t.Fatalf("Unable to perform allocation: %v", err)
	}
	if result.Node.NodeID != 1 || result.StoreID != 1 {
		t.Errorf("expected NodeID 1 and StoreID 1: %+v", result)
	}
}

// TestAllocatorThrottled ensures that when a store is throttled, the replica
// will not be sent to purgatory.
func TestAllocatorThrottled(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper, g, _, a, _ := createTestAllocator()
	defer stopper.Stop()

	// First test to make sure we would send the replica to purgatory.
	_, err := a.AllocateTarget(
		simpleZoneConfig.ReplicaAttrs[0],
		[]roachpb.ReplicaDescriptor{},
		false,
		nil,
	)
	if _, ok := err.(purgatoryError); !ok {
		t.Fatalf("expected a purgatory error, got: %v", err)
	}

	// Second, test the normal case in which we can allocate to the store.
	gossiputil.NewStoreGossiper(g).GossipStores(singleStore, t)
	result, err := a.AllocateTarget(
		simpleZoneConfig.ReplicaAttrs[0],
		[]roachpb.ReplicaDescriptor{},
		false,
		nil,
	)
	if err != nil {
		t.Fatalf("unable to perform allocation: %v", err)
	}
	if result.Node.NodeID != 1 || result.StoreID != 1 {
		t.Errorf("expected NodeID 1 and StoreID 1: %+v", result)
	}

	// Finally, set that store to be throttled and ensure we don't send the
	// replica to purgatory.
	a.storePool.mu.Lock()
	storeDetail, ok := a.storePool.mu.stores[singleStore[0].StoreID]
	if !ok {
		t.Fatalf("store:%d was not found in the store pool", singleStore[0].StoreID)
	}
	storeDetail.throttledUntil = timeutil.Now().Add(24 * time.Hour)
	a.storePool.mu.Unlock()
	_, err = a.AllocateTarget(
		simpleZoneConfig.ReplicaAttrs[0],
		[]roachpb.ReplicaDescriptor{},
		false,
		nil,
	)
	if _, ok := err.(purgatoryError); ok {
		t.Fatalf("expected a non purgatory error, got: %v", err)
	}
}

// TestAllocatorRebalance verifies that rebalance targets are chosen
// randomly from amongst stores over the minAvailCapacityThreshold.
func TestAllocatorRebalance(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper, g, _, a := createTestAllocator()
	defer stopper.Stop()

	stores := []*roachpb.StoreDescriptor{
		{
			StoreID:  1,
			Node:     roachpb.NodeDescriptor{NodeID: 1},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 100},
		},
		{
			StoreID:  2,
			Node:     roachpb.NodeDescriptor{NodeID: 2},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 50},
		},
		{
			StoreID:  3,
			Node:     roachpb.NodeDescriptor{NodeID: 3},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 100 - int64(100*maxFractionUsedThreshold)},
		},
		{
			StoreID:  4,
			Node:     roachpb.NodeDescriptor{NodeID: 4},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: (100 - int64(100*maxFractionUsedThreshold)) / 2},
		},
	}
	gossiputil.NewStoreGossiper(g).GossipStores(stores, t)

	// Every rebalance target must be either stores 1 or 2.
	for i := 0; i < 10; i++ {
		result := a.RebalanceTarget(3, roachpb.Attributes{}, []roachpb.ReplicaDescriptor{})
		if result == nil {
			t.Fatal("nil result")
		}
		if result.StoreID != 1 && result.StoreID != 2 {
			t.Errorf("%d: expected store 1 or 2; got %d", i, result.StoreID)
		}
	}

	// Verify ShouldRebalance results.
	a.options.Deterministic = true
	for i, store := range stores {
		result := a.ShouldRebalance(store.StoreID)
		if expResult := (i >= 2); expResult != result {
			t.Errorf("%d: expected rebalance %t; got %t", i, expResult, result)
		}
	}
}

func TestStorePoolGetStoreDetails(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper, g, _, sp := createTestStorePool(TestTimeUntilStoreDeadOff)
	defer stopper.Stop()
	sg := gossiputil.NewStoreGossiper(g)
	sg.GossipStores(uniqueStore, t)

	if detail := sp.getStoreDetail(roachpb.StoreID(1)); detail.dead {
		t.Errorf("Present storeDetail came back as dead, expected it to be alive. %+v", detail)
	}

	if detail := sp.getStoreDetail(roachpb.StoreID(2)); detail.dead {
		t.Errorf("Absent storeDetail came back as dead, expected it to be alive. %+v", detail)
	}
}

// createCluster generates a new cluster using the provided stopper and the
// number of nodes supplied. Each node will have one store to start.
func createCluster(stopper *stop.Stopper, nodeCount int, epochWriter, actionWriter io.Writer, script Script) *Cluster {
	rand, seed := randutil.NewPseudoRand()
	clock := hlc.NewClock(hlc.UnixNano)
	rpcContext := rpc.NewContext(&base.Context{}, clock, stopper)
	g := gossip.New(rpcContext, gossip.TestInterval, gossip.TestBootstrap)
	storePool := storage.NewStorePool(g, storage.TestTimeUntilStoreDeadOff, stopper)
	c := &Cluster{
		stopper:   stopper,
		clock:     clock,
		rpc:       rpcContext,
		gossip:    g,
		storePool: storePool,
		allocator: storage.MakeAllocator(storePool, storage.RebalancingOptions{
			AllowRebalance: true,
			Deterministic:  true,
		}),
		storeGossiper:   gossiputil.NewStoreGossiper(g),
		nodes:           make(map[roachpb.NodeID]*Node),
		stores:          make(map[roachpb.StoreID]*Store),
		ranges:          make(map[roachpb.RangeID]*Range),
		rangeIDsByStore: make(map[roachpb.StoreID]roachpb.RangeIDSlice),
		rand:            rand,
		seed:            seed,
		epochWriter:     tabwriter.NewWriter(epochWriter, 8, 1, 2, ' ', 0),
		actionWriter:    tabwriter.NewWriter(actionWriter, 8, 1, 2, ' ', 0),
		script:          script,
		epoch:           -1,
	}

	// Add the nodes.
	for i := 0; i < nodeCount; i++ {
		c.addNewNodeWithStore()
	}

	// Add a single range and add to this first node's first store.
	firstRange := c.addRange()
	firstRange.addReplica(c.stores[0])

	c.calculateRangeIDsByStore()

	// Output the first epoch header.
	c.epoch = 0
	c.OutputEpochHeader()
	c.OutputEpoch()
	c.flush()

	return c
}

// TestAllocatorRebalance verifies that only rebalance targets within
// a standard deviation of the mean are chosen.
func TestAllocatorRebalanceByCapacity(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper, g, _, a := createTestAllocator()
	defer stopper.Stop()

	stores := []*roachpb.StoreDescriptor{
		{
			StoreID:  1,
			Node:     roachpb.NodeDescriptor{NodeID: 1},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 50},
		},
		{
			StoreID:  2,
			Node:     roachpb.NodeDescriptor{NodeID: 2},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 50},
		},
		{
			StoreID:  3,
			Node:     roachpb.NodeDescriptor{NodeID: 3},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 50},
		},
		{
			StoreID:  4,
			Node:     roachpb.NodeDescriptor{NodeID: 4},
			Capacity: roachpb.StoreCapacity{Capacity: 100, Available: 80},
		},
	}
	gossiputil.NewStoreGossiper(g).GossipStores(stores, t)

	// Every rebalance target must be store 4 (if not nil).
	for i := 0; i < 10; i++ {
		result := a.RebalanceTarget(1, roachpb.Attributes{}, []roachpb.ReplicaDescriptor{})
		if result != nil && result.StoreID != 4 {
			t.Errorf("expected store 4; got %d", result.StoreID)
		}
	}

	// Verify ShouldRebalance results.
	a.options.Deterministic = true
	for i, store := range stores {
		result := a.ShouldRebalance(store.StoreID)
		if expResult := (i < 3); expResult != result {
			t.Errorf("%d: expected rebalance %t; got %t", i, expResult, result)
		}
	}
}

// TestAllocatorRebalanceByCount verifies that rebalance targets are
// chosen by range counts in the event that available capacities
// exceed the maxAvailCapacityThreshold.
func TestAllocatorRebalanceByCount(t *testing.T) {
	defer leaktest.AfterTest(t)
	stopper, g, _, a := createTestAllocator()
	defer stopper.Stop()

	// Setup the stores so that only one is below the standard deviation threshold.
	stores := []*proto.StoreDescriptor{
		{
			StoreID:  1,
			Node:     proto.NodeDescriptor{NodeID: 1},
			Capacity: proto.StoreCapacity{Capacity: 100, Available: 100, RangeCount: 10},
		},
		{
			StoreID:  2,
			Node:     proto.NodeDescriptor{NodeID: 2},
			Capacity: proto.StoreCapacity{Capacity: 100, Available: 99, RangeCount: 10},
		},
		{
			StoreID:  3,
			Node:     proto.NodeDescriptor{NodeID: 3},
			Capacity: proto.StoreCapacity{Capacity: 100, Available: 98, RangeCount: 10},
		},
		{
			StoreID:  4,
			Node:     proto.NodeDescriptor{NodeID: 4},
			Capacity: proto.StoreCapacity{Capacity: 100, Available: 97, RangeCount: 5},
		},
	}
	gossiputil.NewStoreGossiper(g).GossipStores(stores, t)

	// Every rebalance target must be store 4 (or nil for case of missing the only option).
	for i := 0; i < 10; i++ {
		result := a.RebalanceTarget(proto.Attributes{}, []proto.Replica{})
		if result != nil && result.StoreID != 4 {
			t.Errorf("expected store 4; got %d", result.StoreID)
		}
	}

	// Verify shouldRebalance results.
	for i, store := range stores {
		result := a.shouldRebalance(store)
		if expResult := (i < 3); expResult != result {
			t.Errorf("%d: expected rebalance %t; got %t", i, expResult, result)
		}
	}
}

// TestAllocatorRelaxConstraints verifies that attribute constraints
// will be relaxed in order to match nodes lacking required attributes,
// if necessary to find an allocation target.
func TestAllocatorRelaxConstraints(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper, g, _, a, _ := createTestAllocator()
	defer stopper.Stop()
	gossiputil.NewStoreGossiper(g).GossipStores(multiDCStores, t)

	testCases := []struct {
		required         []string // attribute strings
		existing         []int    // existing store/node ID
		relaxConstraints bool     // allow constraints to be relaxed?
		expID            int      // expected store/node ID on allocate
		expErr           bool
	}{
		// The two stores in the system have attributes:
		//  storeID=1 {"a", "ssd"}
		//  storeID=2 {"b", "ssd"}
		{[]string{"a", "ssd"}, []int{}, true, 1, false},
		{[]string{"a", "ssd"}, []int{1}, true, 2, false},
		{[]string{"a", "ssd"}, []int{1}, false, 0, true},
		{[]string{"a", "ssd"}, []int{1, 2}, true, 0, true},
		{[]string{"b", "ssd"}, []int{}, true, 2, false},
		{[]string{"b", "ssd"}, []int{1}, true, 2, false},
		{[]string{"b", "ssd"}, []int{2}, false, 0, true},
		{[]string{"b", "ssd"}, []int{2}, true, 1, false},
		{[]string{"b", "ssd"}, []int{1, 2}, true, 0, true},
		{[]string{"b", "hdd"}, []int{}, true, 2, false},
		{[]string{"b", "hdd"}, []int{2}, true, 1, false},
		{[]string{"b", "hdd"}, []int{2}, false, 0, true},
		{[]string{"b", "hdd"}, []int{1, 2}, true, 0, true},
		{[]string{"b", "ssd", "gpu"}, []int{}, true, 2, false},
		{[]string{"b", "hdd", "gpu"}, []int{}, true, 2, false},
	}
	for i, test := range testCases {
		var existing []roachpb.ReplicaDescriptor
		for _, id := range test.existing {
			existing = append(existing, roachpb.ReplicaDescriptor{NodeID: roachpb.NodeID(id), StoreID: roachpb.StoreID(id)})
		}
		result, err := a.AllocateTarget(roachpb.Attributes{Attrs: test.required}, existing, test.relaxConstraints, nil)
		if haveErr := (err != nil); haveErr != test.expErr {
			t.Errorf("%d: expected error %t; got %t: %s", i, test.expErr, haveErr, err)
		} else if err == nil && roachpb.StoreID(test.expID) != result.StoreID {
			t.Errorf("%d: expected result to have store %d; got %+v", i, test.expID, result)
		}
	}
}

func TestAllocatorExistingReplica(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper, g, _, a, _ := createTestAllocator()
	defer stopper.Stop()
	gossiputil.NewStoreGossiper(g).GossipStores(sameDCStores, t)
	result, err := a.AllocateTarget(multiDisksConfig.ReplicaAttrs[1], []roachpb.ReplicaDescriptor{
		{
			NodeID:  2,
			StoreID: 2,
		},
	}, false, nil)
	if err != nil {
		t.Fatalf("Unable to perform allocation: %v", err)
	}
	if result.Node.NodeID != 3 || result.StoreID != 4 {
		t.Errorf("expected result to have node 3 and store 4: %+v", result)
	}
}