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scheduler.go
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scheduler.go
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// Copyright 2015, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
/*
Package automation contains code to execute high-level cluster operations
(e.g. resharding) as a series of low-level operations
(e.g. vtctl, shell commands, ...).
*/
package automation
import (
"errors"
"fmt"
"sync"
log "github.com/golang/glog"
automationpb "github.com/youtube/vitess/go/vt/proto/automation"
"golang.org/x/net/context"
)
type schedulerState int32
const (
stateNotRunning schedulerState = iota
stateRunning
stateShuttingDown
stateShutdown
)
type taskCreator func(string) Task
// Scheduler executes automation tasks and maintains the execution state.
type Scheduler struct {
idGenerator IDGenerator
mu sync.Mutex
// Guarded by "mu".
registeredClusterOperations map[string]bool
// Guarded by "mu".
toBeScheduledClusterOperations chan ClusterOperationInstance
// Guarded by "mu".
state schedulerState
// Guarded by "taskCreatorMu". May be overriden by testing code.
taskCreator taskCreator
taskCreatorMu sync.Mutex
pendingOpsWg *sync.WaitGroup
muOpList sync.Mutex
// Guarded by "muOpList".
// The key of the map is ClusterOperationInstance.ID.
// This map contains a copy of the ClusterOperationInstance which is currently processed.
// The scheduler may update the copy with the latest status.
activeClusterOperations map[string]ClusterOperationInstance
// Guarded by "muOpList".
// The key of the map is ClusterOperationInstance.ID.
finishedClusterOperations map[string]ClusterOperationInstance
}
// NewScheduler creates a new instance.
func NewScheduler() (*Scheduler, error) {
defaultClusterOperations := map[string]bool{
"HorizontalReshardingTask": true,
"VerticalSplitTask": true,
}
s := &Scheduler{
registeredClusterOperations: defaultClusterOperations,
idGenerator: IDGenerator{},
toBeScheduledClusterOperations: make(chan ClusterOperationInstance, 10),
state: stateNotRunning,
taskCreator: defaultTaskCreator,
pendingOpsWg: &sync.WaitGroup{},
activeClusterOperations: make(map[string]ClusterOperationInstance),
finishedClusterOperations: make(map[string]ClusterOperationInstance),
}
return s, nil
}
func (s *Scheduler) registerClusterOperation(clusterOperationName string) {
s.mu.Lock()
defer s.mu.Unlock()
s.registeredClusterOperations[clusterOperationName] = true
}
// Run processes queued cluster operations.
func (s *Scheduler) Run() {
s.mu.Lock()
s.state = stateRunning
s.mu.Unlock()
s.startProcessRequestsLoop()
}
func (s *Scheduler) startProcessRequestsLoop() {
// Use a WaitGroup instead of just a done channel, because we want
// to be able to shut down the scheduler even if Run() was never executed.
s.pendingOpsWg.Add(1)
go s.processRequestsLoop()
}
func (s *Scheduler) processRequestsLoop() {
defer s.pendingOpsWg.Done()
for op := range s.toBeScheduledClusterOperations {
s.processClusterOperation(op)
}
log.Infof("Stopped processing loop for ClusterOperations.")
}
func (s *Scheduler) processClusterOperation(clusterOp ClusterOperationInstance) {
if clusterOp.State == automationpb.ClusterOperationState_CLUSTER_OPERATION_DONE {
log.Infof("ClusterOperation: %v skipping because it is already done. Details: %v", clusterOp.Id, clusterOp)
return
}
log.Infof("ClusterOperation: %v running. Details: %v", clusterOp.Id, clusterOp)
clusterOpLoop:
for i := 0; i < len(clusterOp.SerialTasks); i++ {
taskContainer := clusterOp.SerialTasks[i]
for _, taskProto := range taskContainer.ParallelTasks {
newTaskContainers, output, err := s.runTask(taskProto, clusterOp.Id)
if err != nil {
MarkTaskFailed(taskProto, output, err)
clusterOp.Error = err.Error()
break clusterOpLoop
} else {
MarkTaskSucceeded(taskProto, output)
}
if newTaskContainers != nil {
// Make sure all new tasks do not miss any required parameters.
err := s.validateTaskContainers(newTaskContainers)
if err != nil {
err = fmt.Errorf("Task: %v (%v/%v) emitted a new task which is not valid. Error: %v", taskProto.Name, clusterOp.Id, taskProto.Id, err)
log.Error(err)
MarkTaskFailed(taskProto, output, err)
clusterOp.Error = err.Error()
break clusterOpLoop
}
clusterOp.InsertTaskContainers(newTaskContainers, i+1)
log.Infof("ClusterOperation: %v %d new task containers added by %v (%v/%v). Updated ClusterOperation: %v",
clusterOp.Id, len(newTaskContainers), taskProto.Name, clusterOp.Id, taskProto.Id, clusterOp)
}
s.Checkpoint(clusterOp)
}
}
clusterOp.State = automationpb.ClusterOperationState_CLUSTER_OPERATION_DONE
log.Infof("ClusterOperation: %v finished. Details: %v", clusterOp.Id, clusterOp)
s.Checkpoint(clusterOp)
// Move operation from active to finished.
s.muOpList.Lock()
defer s.muOpList.Unlock()
if _, ok := s.activeClusterOperations[clusterOp.Id]; !ok {
panic("Pending ClusterOperation was not recorded as active, but should have.")
}
delete(s.activeClusterOperations, clusterOp.Id)
s.finishedClusterOperations[clusterOp.Id] = clusterOp
}
func (s *Scheduler) runTask(taskProto *automationpb.Task, clusterOpID string) ([]*automationpb.TaskContainer, string, error) {
if taskProto.State == automationpb.TaskState_DONE {
// Task is already done (e.g. because we resume from a checkpoint).
if taskProto.Error != "" {
log.Errorf("Task: %v (%v/%v) failed before. Aborting the ClusterOperation. Error: %v Details: %v", taskProto.Name, clusterOpID, taskProto.Id, taskProto.Error, taskProto)
return nil, "", errors.New(taskProto.Error)
}
log.Infof("Task: %v (%v/%v) skipped because it is already done. Full Details: %v", taskProto.Name, clusterOpID, taskProto.Id, taskProto)
return nil, taskProto.Output, nil
}
task, err := s.createTaskInstance(taskProto.Name)
if err != nil {
log.Errorf("Task: %v (%v/%v) could not be instantiated. Error: %v Details: %v", taskProto.Name, clusterOpID, taskProto.Id, err, taskProto)
return nil, "", err
}
taskProto.State = automationpb.TaskState_RUNNING
log.Infof("Task: %v (%v/%v) running. Details: %v", taskProto.Name, clusterOpID, taskProto.Id, taskProto)
newTaskContainers, output, err := task.Run(taskProto.Parameters)
log.Infof("Task: %v (%v/%v) finished. newTaskContainers: %v, output: %v, error: %v", taskProto.Name, clusterOpID, taskProto.Id, newTaskContainers, output, err)
return newTaskContainers, output, err
}
func (s *Scheduler) validateTaskContainers(newTaskContainers []*automationpb.TaskContainer) error {
for _, newTaskContainer := range newTaskContainers {
for _, newTaskProto := range newTaskContainer.ParallelTasks {
err := s.validateTaskSpecification(newTaskProto.Name, newTaskProto.Parameters)
if err != nil {
return fmt.Errorf("error: %v task: %v", err, newTaskProto)
}
}
}
return nil
}
func defaultTaskCreator(taskName string) Task {
switch taskName {
case "HorizontalReshardingTask":
return &HorizontalReshardingTask{}
case "VerticalSplitTask":
return &VerticalSplitTask{}
case "CopySchemaShardTask":
return &CopySchemaShardTask{}
case "MigrateServedFromTask":
return &MigrateServedFromTask{}
case "MigrateServedTypesTask":
return &MigrateServedTypesTask{}
case "RebuildKeyspaceGraph":
return &RebuildKeyspaceGraphTask{}
case "SplitCloneTask":
return &SplitCloneTask{}
case "SplitDiffTask":
return &SplitDiffTask{}
case "VerticalSplitCloneTask":
return &VerticalSplitCloneTask{}
case "VerticalSplitDiffTask":
return &VerticalSplitDiffTask{}
case "WaitForFilteredReplicationTask":
return &WaitForFilteredReplicationTask{}
default:
return nil
}
}
func (s *Scheduler) setTaskCreator(creator taskCreator) {
s.taskCreatorMu.Lock()
defer s.taskCreatorMu.Unlock()
s.taskCreator = creator
}
func (s *Scheduler) validateTaskSpecification(taskName string, parameters map[string]string) error {
taskInstanceForParametersCheck, err := s.createTaskInstance(taskName)
if err != nil {
return err
}
errParameters := validateParameters(taskInstanceForParametersCheck, parameters)
if errParameters != nil {
return errParameters
}
return nil
}
func (s *Scheduler) createTaskInstance(taskName string) (Task, error) {
s.taskCreatorMu.Lock()
taskCreator := s.taskCreator
s.taskCreatorMu.Unlock()
task := taskCreator(taskName)
if task == nil {
return nil, fmt.Errorf("no implementation found for: %v", taskName)
}
return task, nil
}
// validateParameters returns an error if not all required parameters are provided in "parameters".
// Unknown parameters (neither required nor optional) result in an error.
func validateParameters(task Task, parameters map[string]string) error {
validParams := make(map[string]bool)
var missingParams []string
for _, reqParam := range task.RequiredParameters() {
if _, ok := parameters[reqParam]; ok {
validParams[reqParam] = true
} else {
missingParams = append(missingParams, reqParam)
}
}
if len(missingParams) > 0 {
return fmt.Errorf("required parameters are missing: %v", missingParams)
}
for _, optParam := range task.OptionalParameters() {
validParams[optParam] = true
}
for param := range parameters {
if !validParams[param] {
return fmt.Errorf("parameter %v is not allowed. Allowed required parameters: %v optional parameters: %v",
param, task.RequiredParameters(), task.OptionalParameters())
}
}
return nil
}
// EnqueueClusterOperation can be used to start a new cluster operation.
func (s *Scheduler) EnqueueClusterOperation(ctx context.Context, req *automationpb.EnqueueClusterOperationRequest) (*automationpb.EnqueueClusterOperationResponse, error) {
s.mu.Lock()
defer s.mu.Unlock()
if s.state != stateRunning {
return nil, fmt.Errorf("scheduler is not running. State: %v", s.state)
}
if s.registeredClusterOperations[req.Name] != true {
return nil, fmt.Errorf("no ClusterOperation with name: %v is registered", req.Name)
}
err := s.validateTaskSpecification(req.Name, req.Parameters)
if err != nil {
return nil, err
}
clusterOpID := s.idGenerator.GetNextID()
taskIDGenerator := IDGenerator{}
initialTask := NewTaskContainerWithSingleTask(req.Name, req.Parameters)
clusterOp := NewClusterOperationInstance(clusterOpID, initialTask, &taskIDGenerator)
s.muOpList.Lock()
s.activeClusterOperations[clusterOpID] = clusterOp.Clone()
s.muOpList.Unlock()
s.toBeScheduledClusterOperations <- clusterOp
return &automationpb.EnqueueClusterOperationResponse{
Id: clusterOp.Id,
}, nil
}
// findClusterOp checks for a given ClusterOperation ID if it's in the list of active or finished operations.
func (s *Scheduler) findClusterOp(id string) (ClusterOperationInstance, error) {
var ok bool
var clusterOp ClusterOperationInstance
s.muOpList.Lock()
defer s.muOpList.Unlock()
clusterOp, ok = s.activeClusterOperations[id]
if !ok {
clusterOp, ok = s.finishedClusterOperations[id]
}
if !ok {
return clusterOp, fmt.Errorf("ClusterOperation with id: %v not found", id)
}
return clusterOp.Clone(), nil
}
// Checkpoint should be called every time the state of the cluster op changes.
// It is used to update the copy of the state in activeClusterOperations.
func (s *Scheduler) Checkpoint(clusterOp ClusterOperationInstance) {
// TODO(mberlin): Add here support for persistent checkpoints.
s.muOpList.Lock()
defer s.muOpList.Unlock()
s.activeClusterOperations[clusterOp.Id] = clusterOp.Clone()
}
// GetClusterOperationDetails can be used to query the full details of active or finished operations.
func (s *Scheduler) GetClusterOperationDetails(ctx context.Context, req *automationpb.GetClusterOperationDetailsRequest) (*automationpb.GetClusterOperationDetailsResponse, error) {
clusterOp, err := s.findClusterOp(req.Id)
if err != nil {
return nil, err
}
return &automationpb.GetClusterOperationDetailsResponse{
ClusterOp: &clusterOp.ClusterOperation,
}, nil
}
// ShutdownAndWait shuts down the scheduler and waits infinitely until all pending cluster operations have finished.
func (s *Scheduler) ShutdownAndWait() {
s.mu.Lock()
if s.state != stateShuttingDown {
s.state = stateShuttingDown
close(s.toBeScheduledClusterOperations)
}
s.mu.Unlock()
log.Infof("Scheduler was shut down. Waiting for pending ClusterOperations to finish.")
s.pendingOpsWg.Wait()
s.mu.Lock()
s.state = stateShutdown
s.mu.Unlock()
log.Infof("All pending ClusterOperations finished.")
}