Implement 'batch mode' for persisting allocations on the client.

Fixes #9047, see problem details there.

As a solution, we use BoltDB's 'Batch' mode that combines multiple
parallel writes into small number of transactions. See
https://github.com/boltdb/bolt#batch-read-write-transactions for
more information.

client/allocrunner/alloc_runner.go

@@ -862,7 +862,7 @@ func (ar *allocRunner) destroyImpl() {
 
 	// Cleanup state db; while holding the lock to avoid
 	// a race periodic PersistState that may resurrect the alloc
-	if err := ar.stateDB.DeleteAllocationBucket(ar.id); err != nil {
+	if err := ar.stateDB.DeleteAllocationBucket(ar.id, false); err != nil {
 		ar.logger.Warn("failed to delete allocation state", "error", err)
 	}
 
@@ -877,36 +877,37 @@ func (ar *allocRunner) destroyImpl() {
 	ar.destroyedLock.Unlock()
 }
 
-func (ar *allocRunner) PersistState() error {
+func (ar *allocRunner) PersistState(inBatch bool) error {
 	ar.destroyedLock.Lock()
 	defer ar.destroyedLock.Unlock()
 
 	if ar.destroyed {
-		err := ar.stateDB.DeleteAllocationBucket(ar.id)
+		err := ar.stateDB.DeleteAllocationBucket(ar.id, inBatch)
 		if err != nil {
 			ar.logger.Warn("failed to delete allocation bucket", "error", err)
 		}
 		return nil
 	}
 
 	// persist network status, wrapping in a func to release state lock as early as possible
-	if err := func() error {
+	persistNetworkStatus := func() error {
 		ar.stateLock.Lock()
 		defer ar.stateLock.Unlock()
 		if ar.state.NetworkStatus != nil {
-			if err := ar.stateDB.PutNetworkStatus(ar.id, ar.state.NetworkStatus); err != nil {
+			if err := ar.stateDB.PutNetworkStatus(ar.id, ar.state.NetworkStatus, inBatch); err != nil {
 				return err
 			}
 		}
 		return nil
-	}(); err != nil {
+	}
+	if err := persistNetworkStatus(); err != nil {
 		return err
 	}
 
 	// TODO: consider persisting deployment state along with task status.
 	// While we study why only the alloc is persisted, I opted to maintain current
 	// behavior and not risk adding yet more IO calls unnecessarily.
-	return ar.stateDB.PutAllocation(ar.Alloc())
+	return ar.stateDB.PutAllocation(ar.Alloc(), inBatch)
 }
 
 // Destroy the alloc runner by stopping it if it is still running and cleaning

client/allocrunner/alloc_runner_test.go

@@ -1452,7 +1452,7 @@ func TestAllocRunner_PersistState_Destroyed(t *testing.T) {
 	}
 
 	// test final persisted state upon completion
-	require.NoError(t, ar.PersistState())
+	require.NoError(t, ar.PersistState(false))
 	allocs, _, err := conf.StateDB.GetAllAllocations()
 	require.NoError(t, err)
 	require.Len(t, allocs, 1)
@@ -1477,7 +1477,7 @@ func TestAllocRunner_PersistState_Destroyed(t *testing.T) {
 	require.Nil(t, ts)
 
 	// check that DB alloc is empty after persisting state of destroyed AR
-	ar.PersistState()
+	require.NoError(t, ar.PersistState(false))
 	allocs, _, err = conf.StateDB.GetAllAllocations()
 	require.NoError(t, err)
 	require.Empty(t, allocs)

client/client.go

@@ -148,7 +148,7 @@ type AllocRunner interface {
 	ShutdownCh() <-chan struct{}
 	Signal(taskName, signal string) error
 	GetTaskEventHandler(taskName string) drivermanager.EventHandler
-	PersistState() error
+	PersistState(inBatch bool) error
 
 	RestartTask(taskName string, taskEvent *structs.TaskEvent) error
 	RestartAll(taskEvent *structs.TaskEvent) error
@@ -1221,7 +1221,7 @@ func (c *Client) saveState() error {
 
 	for id, ar := range runners {
 		go func(id string, ar AllocRunner) {
-			err := ar.PersistState()
+			err := ar.PersistState(true) // Persist in 'batch mode', to minimize # of transactions.
 			if err != nil {
 				c.logger.Error("error saving alloc state", "error", err, "alloc_id", id)
 				l.Lock()
@@ -2333,7 +2333,7 @@ func (c *Client) updateAlloc(update *structs.Allocation) {
 	}
 
 	// Update local copy of alloc
-	if err := c.stateDB.PutAllocation(update); err != nil {
+	if err := c.stateDB.PutAllocation(update, false); err != nil {
 		c.logger.Error("error persisting updated alloc locally", "error", err, "alloc_id", update.ID)
 	}
 
@@ -2354,7 +2354,7 @@ func (c *Client) addAlloc(alloc *structs.Allocation, migrateToken string) error
 
 	// Initialize local copy of alloc before creating the alloc runner so
 	// we can't end up with an alloc runner that does not have an alloc.
-	if err := c.stateDB.PutAllocation(alloc); err != nil {
+	if err := c.stateDB.PutAllocation(alloc, false); err != nil {
 		return err
 	}
 

client/client_test.go

@@ -1591,7 +1591,7 @@ func TestClient_hasLocalState(t *testing.T) {
 
 	t.Run("plain alloc", func(t *testing.T) {
 		alloc := mock.BatchAlloc()
-		c.stateDB.PutAllocation(alloc)
+		c.stateDB.PutAllocation(alloc, false)
 
 		require.False(t, c.hasLocalState(alloc))
 	})
@@ -1601,7 +1601,7 @@ func TestClient_hasLocalState(t *testing.T) {
 		taskName := alloc.Job.LookupTaskGroup(alloc.TaskGroup).Tasks[0].Name
 		ls := &trstate.LocalState{}
 
-		c.stateDB.PutAllocation(alloc)
+		c.stateDB.PutAllocation(alloc, false)
 		c.stateDB.PutTaskRunnerLocalState(alloc.ID, taskName, ls)
 
 		require.True(t, c.hasLocalState(alloc))
@@ -1614,7 +1614,7 @@ func TestClient_hasLocalState(t *testing.T) {
 			State: structs.TaskStateRunning,
 		}
 
-		c.stateDB.PutAllocation(alloc)
+		c.stateDB.PutAllocation(alloc, false)
 		c.stateDB.PutTaskState(alloc.ID, taskName, ts)
 
 		require.True(t, c.hasLocalState(alloc))

client/state/db_test.go

@@ -4,6 +4,7 @@ import (
 	"io/ioutil"
 	"os"
 	"reflect"
+	"sync"
 	"testing"
 
 	trstate "github.com/hashicorp/nomad/client/allocrunner/taskrunner/state"
@@ -57,7 +58,7 @@ func testDB(t *testing.T, f func(*testing.T, StateDB)) {
 	}
 }
 
-// TestStateDB asserts the behavior of GetAllAllocations, PutAllocation, and
+// TestStateDB_Allocations asserts the behavior of GetAllAllocations, PutAllocation, and
 // DeleteAllocationBucket for all operational StateDB implementations.
 func TestStateDB_Allocations(t *testing.T) {
 	t.Parallel()
@@ -77,8 +78,8 @@ func TestStateDB_Allocations(t *testing.T) {
 		alloc1 := mock.Alloc()
 		alloc2 := mock.BatchAlloc()
 
-		require.NoError(db.PutAllocation(alloc1))
-		require.NoError(db.PutAllocation(alloc2))
+		require.NoError(db.PutAllocation(alloc1, false))
+		require.NoError(db.PutAllocation(alloc2, false))
 
 		// Retrieve them
 		allocs, errs, err = db.GetAllAllocations()
@@ -106,7 +107,7 @@ func TestStateDB_Allocations(t *testing.T) {
 
 		// Add another
 		alloc3 := mock.SystemAlloc()
-		require.NoError(db.PutAllocation(alloc3))
+		require.NoError(db.PutAllocation(alloc3, false))
 		allocs, errs, err = db.GetAllAllocations()
 		require.NoError(err)
 		require.NotNil(allocs)
@@ -118,14 +119,14 @@ func TestStateDB_Allocations(t *testing.T) {
 		require.Empty(errs)
 
 		// Deleting a nonexistent alloc is a noop
-		require.NoError(db.DeleteAllocationBucket("asdf"))
+		require.NoError(db.DeleteAllocationBucket("asdf", false))
 		allocs, _, err = db.GetAllAllocations()
 		require.NoError(err)
 		require.NotNil(allocs)
 		require.Len(allocs, 3)
 
 		// Delete alloc1
-		require.NoError(db.DeleteAllocationBucket(alloc1.ID))
+		require.NoError(db.DeleteAllocationBucket(alloc1.ID, false))
 		allocs, errs, err = db.GetAllAllocations()
 		require.NoError(err)
 		require.NotNil(allocs)
@@ -137,6 +138,102 @@ func TestStateDB_Allocations(t *testing.T) {
 	})
 }
 
+// TestStateDB_Batch asserts the behavior of PutAllocation, PutNetworkStatus and
+// DeleteAllocationBucket in batch mode, for all operational StateDB implementations.
+func TestStateDB_Batch(t *testing.T) {
+	t.Parallel()
+
+	testDB(t, func(t *testing.T, db StateDB) {
+		require := require.New(t)
+
+		// For BoltDB, get initial tx_id
+		var getTxID func() int
+		var prevTxID int
+		if boltStateDB, ok := db.(*BoltStateDB); ok {
+			boltdb := boltStateDB.DB().BoltDB()
+			getTxID = func() int {
+				tx, err := boltdb.Begin(true)
+				require.NoError(err)
+				defer tx.Rollback()
+				return tx.ID()
+			}
+			prevTxID = getTxID()
+		}
+
+		// Write 1000 allocations and network statuses in batch mode
+		var allocs []*structs.Allocation
+		for i := 0; i < 1000; i++ {
+			allocs = append(allocs, mock.Alloc())
+		}
+		var wg sync.WaitGroup
+		for _, alloc := range allocs {
+			wg.Add(1)
+			go func(alloc *structs.Allocation) {
+				require.NoError(db.PutNetworkStatus(alloc.ID, mock.AllocNetworkStatus(), true))
+				require.NoError(db.PutAllocation(alloc, true))
+				wg.Done()
+			}(alloc)
+		}
+		wg.Wait()
+
+		// Check BoltDB actually combined PutAllocation calls into much fewer transactions.
+		// The actual number of transactions depends on how fast the goroutines are spawned,
+		// with every 10ms period saved in a separate transaction (see boltdb MaxBatchDelay
+		// and MaxBatchSize parameters).
+		if getTxID != nil {
+			numTransactions := getTxID() - prevTxID
+			require.Less(numTransactions, 10)
+			prevTxID = getTxID()
+		}
+
+		// Retrieve allocs and make sure they are the same (order can differ)
+		readAllocs, errs, err := db.GetAllAllocations()
+		require.NoError(err)
+		require.NotNil(readAllocs)
+		require.Len(readAllocs, len(allocs))
+		require.NotNil(errs)
+		require.Empty(errs)
+
+		readAllocsById := make(map[string]*structs.Allocation)
+		for _, readAlloc := range readAllocs {
+			readAllocsById[readAlloc.ID] = readAlloc
+		}
+		for _, alloc := range allocs {
+			readAlloc, ok := readAllocsById[alloc.ID]
+			if !ok {
+				t.Fatalf("no alloc with ID=%q", alloc.ID)
+			}
+			if !reflect.DeepEqual(readAlloc, alloc) {
+				pretty.Ldiff(t, readAlloc, alloc)
+				t.Fatalf("alloc %q unequal", alloc.ID)
+			}
+		}
+
+		// Delete all allocs in batch mode
+		for _, alloc := range allocs {
+			wg.Add(1)
+			go func(alloc *structs.Allocation) {
+				require.NoError(db.DeleteAllocationBucket(alloc.ID, true))
+				wg.Done()
+			}(alloc)
+		}
+		wg.Wait()
+
+		// Check BoltDB combined DeleteAllocationBucket calls into much fewer transactions.
+		if getTxID != nil {
+			numTransactions := getTxID() - prevTxID
+			require.Less(numTransactions, 10)
+			prevTxID = getTxID()
+		}
+
+		// Check all allocs were deleted.
+		readAllocs, errs, err = db.GetAllAllocations()
+		require.NoError(err)
+		require.Empty(readAllocs)
+		require.Empty(errs)
+	})
+}
+
 // TestStateDB_TaskState asserts the behavior of task state related StateDB
 // methods.
 func TestStateDB_TaskState(t *testing.T) {

client/state/errdb.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/hashicorp/nomad/client/allocrunner/taskrunner/state"
 	dmstate "github.com/hashicorp/nomad/client/devicemanager/state"
+	"github.com/hashicorp/nomad/client/dynamicplugins"
 	driverstate "github.com/hashicorp/nomad/client/pluginmanager/drivermanager/state"
 	"github.com/hashicorp/nomad/nomad/structs"
 )
@@ -27,7 +28,7 @@ func (m *ErrDB) GetAllAllocations() ([]*structs.Allocation, map[string]error, er
 	return m.Allocs, nil, nil
 }
 
-func (m *ErrDB) PutAllocation(alloc *structs.Allocation) error {
+func (m *ErrDB) PutAllocation(alloc *structs.Allocation, inBatch bool) error {
 	return fmt.Errorf("Error!")
 }
 
@@ -43,7 +44,7 @@ func (m *ErrDB) GetNetworkStatus(allocID string) (*structs.AllocNetworkStatus, e
 	return nil, fmt.Errorf("Error!")
 }
 
-func (m *ErrDB) PutNetworkStatus(allocID string, ns *structs.AllocNetworkStatus) error {
+func (m *ErrDB) PutNetworkStatus(allocID string, ns *structs.AllocNetworkStatus, inBatch bool) error {
 	return fmt.Errorf("Error!")
 }
 
@@ -63,14 +64,22 @@ func (m *ErrDB) DeleteTaskBucket(allocID, taskName string) error {
 	return fmt.Errorf("Error!")
 }
 
-func (m *ErrDB) DeleteAllocationBucket(allocID string) error {
+func (m *ErrDB) DeleteAllocationBucket(allocID string, inBatch bool) error {
 	return fmt.Errorf("Error!")
 }
 
 func (m *ErrDB) PutDevicePluginState(ps *dmstate.PluginState) error {
 	return fmt.Errorf("Error!")
 }
 
+func (m *ErrDB) GetDynamicPluginRegistryState() (*dynamicplugins.RegistryState, error) {
+	return nil, fmt.Errorf("Error!")
+}
+
+func (m *ErrDB) PutDynamicPluginRegistryState(state *dynamicplugins.RegistryState) error {
+	return fmt.Errorf("Error!")
+}
+
 // GetDevicePluginState stores the device manager's plugin state or returns an
 // error.
 func (m *ErrDB) GetDevicePluginState() (*dmstate.PluginState, error) {
@@ -88,3 +97,6 @@ func (m *ErrDB) PutDriverPluginState(ps *driverstate.PluginState) error {
 func (m *ErrDB) Close() error {
 	return fmt.Errorf("Error!")
 }
+
+// Ensure *ErrDB implements StateDB
+var _ StateDB = (*ErrDB)(nil)

client/state/interface.go

@@ -24,9 +24,10 @@ type StateDB interface {
 	// If a single error is returned then both allocations and the map will be nil.
 	GetAllAllocations() ([]*structs.Allocation, map[string]error, error)
 
-	// PulAllocation stores an allocation or returns an error if it could
-	// not be stored.
-	PutAllocation(*structs.Allocation) error
+	// PutAllocation stores an allocation or returns an error if it could
+	// not be stored. inBatch parameter enables performance optimization when
+	// multiple allocations are expected to be saved in parallel.
+	PutAllocation(alloc *structs.Allocation, inBatch bool) error
 
 	// Get/Put DeploymentStatus get and put the allocation's deployment
 	// status. It may be nil.
@@ -36,7 +37,7 @@ type StateDB interface {
 	// Get/Put NetworkStatus get and put the allocation's network
 	// status. It may be nil.
 	GetNetworkStatus(allocID string) (*structs.AllocNetworkStatus, error)
-	PutNetworkStatus(allocID string, ns *structs.AllocNetworkStatus) error
+	PutNetworkStatus(allocID string, ns *structs.AllocNetworkStatus, inBatch bool) error
 
 	// GetTaskRunnerState returns the LocalState and TaskState for a
 	// TaskRunner. Either state may be nil if it is not found, but if an
@@ -57,7 +58,7 @@ type StateDB interface {
 
 	// DeleteAllocationBucket deletes an allocation's state bucket if it
 	// exists. No error is returned if it does not exist.
-	DeleteAllocationBucket(allocID string) error
+	DeleteAllocationBucket(allocID string, inBatch bool) error
 
 	// GetDevicePluginState is used to retrieve the device manager's plugin
 	// state.