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task_runner.go
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task_runner.go
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package client
import (
"crypto/md5"
"encoding/hex"
"fmt"
"log"
"os"
"path/filepath"
"sync"
"time"
"github.com/hashicorp/go-multierror"
"github.com/hashicorp/nomad/client/config"
"github.com/hashicorp/nomad/client/driver"
"github.com/hashicorp/nomad/client/getter"
"github.com/hashicorp/nomad/nomad/structs"
"github.com/mitchellh/hashstructure"
cstructs "github.com/hashicorp/nomad/client/driver/structs"
)
const (
// killBackoffBaseline is the baseline time for exponential backoff while
// killing a task.
killBackoffBaseline = 5 * time.Second
// killBackoffLimit is the the limit of the exponential backoff for killing
// the task.
killBackoffLimit = 2 * time.Minute
// killFailureLimit is how many times we will attempt to kill a task before
// giving up and potentially leaking resources.
killFailureLimit = 5
)
// TaskRunner is used to wrap a task within an allocation and provide the execution context.
type TaskRunner struct {
config *config.Config
updater TaskStateUpdater
logger *log.Logger
ctx *driver.ExecContext
alloc *structs.Allocation
restartTracker *RestartTracker
consulService *ConsulService
task *structs.Task
updateCh chan *structs.Allocation
handle driver.DriverHandle
handleLock sync.Mutex
// artifactsDownloaded tracks whether the tasks artifacts have been
// downloaded
artifactsDownloaded bool
destroy bool
destroyCh chan struct{}
destroyLock sync.Mutex
waitCh chan struct{}
}
// taskRunnerState is used to snapshot the state of the task runner
type taskRunnerState struct {
Version string
Task *structs.Task
HandleID string
}
// TaskStateUpdater is used to signal that tasks state has changed.
type TaskStateUpdater func(taskName, state string, event *structs.TaskEvent)
// NewTaskRunner is used to create a new task context
func NewTaskRunner(logger *log.Logger, config *config.Config,
updater TaskStateUpdater, ctx *driver.ExecContext,
alloc *structs.Allocation, task *structs.Task,
consulService *ConsulService) *TaskRunner {
// Merge in the task resources
task.Resources = alloc.TaskResources[task.Name]
// Build the restart tracker.
tg := alloc.Job.LookupTaskGroup(alloc.TaskGroup)
if tg == nil {
logger.Printf("[ERR] client: alloc '%s' for missing task group '%s'", alloc.ID, alloc.TaskGroup)
return nil
}
restartTracker := newRestartTracker(tg.RestartPolicy, alloc.Job.Type)
tc := &TaskRunner{
config: config,
updater: updater,
logger: logger,
restartTracker: restartTracker,
consulService: consulService,
ctx: ctx,
alloc: alloc,
task: task,
updateCh: make(chan *structs.Allocation, 64),
destroyCh: make(chan struct{}),
waitCh: make(chan struct{}),
}
// Set the state to pending.
tc.updater(task.Name, structs.TaskStatePending, structs.NewTaskEvent(structs.TaskReceived))
return tc
}
// WaitCh returns a channel to wait for termination
func (r *TaskRunner) WaitCh() <-chan struct{} {
return r.waitCh
}
// stateFilePath returns the path to our state file
func (r *TaskRunner) stateFilePath() string {
// Get the MD5 of the task name
hashVal := md5.Sum([]byte(r.task.Name))
hashHex := hex.EncodeToString(hashVal[:])
dirName := fmt.Sprintf("task-%s", hashHex)
// Generate the path
path := filepath.Join(r.config.StateDir, "alloc", r.alloc.ID,
dirName, "state.json")
return path
}
// RestoreState is used to restore our state
func (r *TaskRunner) RestoreState() error {
// Load the snapshot
var snap taskRunnerState
if err := restoreState(r.stateFilePath(), &snap); err != nil {
return err
}
// Restore fields
r.task = snap.Task
// Restore the driver
if snap.HandleID != "" {
driver, err := r.createDriver()
if err != nil {
return err
}
handle, err := driver.Open(r.ctx, snap.HandleID)
// In the case it fails, we relaunch the task in the Run() method.
if err != nil {
r.logger.Printf("[ERR] client: failed to open handle to task '%s' for alloc '%s': %v",
r.task.Name, r.alloc.ID, err)
return nil
}
r.handleLock.Lock()
r.handle = handle
// If we have previously created the driver, the artifacts have been
// downloaded.
r.artifactsDownloaded = true
r.handleLock.Unlock()
}
return nil
}
// SaveState is used to snapshot our state
func (r *TaskRunner) SaveState() error {
snap := taskRunnerState{
Task: r.task,
Version: r.config.Version,
}
r.handleLock.Lock()
if r.handle != nil {
snap.HandleID = r.handle.ID()
}
r.handleLock.Unlock()
return persistState(r.stateFilePath(), &snap)
}
// DestroyState is used to cleanup after ourselves
func (r *TaskRunner) DestroyState() error {
return os.RemoveAll(r.stateFilePath())
}
// setState is used to update the state of the task runner
func (r *TaskRunner) setState(state string, event *structs.TaskEvent) {
// Persist our state to disk.
if err := r.SaveState(); err != nil {
r.logger.Printf("[ERR] client: failed to save state of Task Runner: %v", r.task.Name)
}
// Indicate the task has been updated.
r.updater(r.task.Name, state, event)
}
// createDriver makes a driver for the task
func (r *TaskRunner) createDriver() (driver.Driver, error) {
taskEnv, err := driver.GetTaskEnv(r.ctx.AllocDir, r.config.Node, r.task, r.alloc)
if err != nil {
err = fmt.Errorf("failed to create driver '%s' for alloc %s: %v",
r.task.Driver, r.alloc.ID, err)
r.logger.Printf("[ERR] client: %s", err)
return nil, err
}
driverCtx := driver.NewDriverContext(r.task.Name, r.config, r.config.Node, r.logger, taskEnv)
driver, err := driver.NewDriver(r.task.Driver, driverCtx)
if err != nil {
err = fmt.Errorf("failed to create driver '%s' for alloc %s: %v",
r.task.Driver, r.alloc.ID, err)
r.logger.Printf("[ERR] client: %s", err)
return nil, err
}
return driver, err
}
// Run is a long running routine used to manage the task
func (r *TaskRunner) Run() {
defer close(r.waitCh)
r.logger.Printf("[DEBUG] client: starting task context for '%s' (alloc '%s')",
r.task.Name, r.alloc.ID)
r.run()
return
}
func (r *TaskRunner) run() {
// Predeclare things so we an jump to the RESTART
var handleEmpty bool
for {
// Download the task's artifacts
if !r.artifactsDownloaded && len(r.task.Artifacts) > 0 {
r.setState(structs.TaskStatePending, structs.NewTaskEvent(structs.TaskDownloadingArtifacts))
taskDir, ok := r.ctx.AllocDir.TaskDirs[r.task.Name]
if !ok {
err := fmt.Errorf("task directory couldn't be found")
r.setState(structs.TaskStateDead, structs.NewTaskEvent(structs.TaskDriverFailure).SetDriverError(err))
r.logger.Printf("[ERR] client: task directory for alloc %q task %q couldn't be found", r.alloc.ID, r.task.Name)
// Non-restartable error
return
}
for _, artifact := range r.task.Artifacts {
if err := getter.GetArtifact(artifact, taskDir, r.logger); err != nil {
r.setState(structs.TaskStateDead,
structs.NewTaskEvent(structs.TaskArtifactDownloadFailed).SetDownloadError(err))
r.restartTracker.SetStartError(cstructs.NewRecoverableError(err, true))
goto RESTART
}
}
r.artifactsDownloaded = true
}
// Start the task if not yet started or it is being forced. This logic
// is necessary because in the case of a restore the handle already
// exists.
r.handleLock.Lock()
handleEmpty = r.handle == nil
r.handleLock.Unlock()
if handleEmpty {
startErr := r.startTask()
r.restartTracker.SetStartError(startErr)
if startErr != nil {
r.setState(structs.TaskStateDead, structs.NewTaskEvent(structs.TaskDriverFailure).SetDriverError(startErr))
goto RESTART
}
}
// Mark the task as started and register it with Consul.
r.setState(structs.TaskStateRunning, structs.NewTaskEvent(structs.TaskStarted))
r.consulService.Register(r.task, r.alloc)
// Wait for updates
WAIT:
for {
select {
case waitRes := <-r.handle.WaitCh():
// De-Register the services belonging to the task from consul
r.consulService.Deregister(r.task, r.alloc)
if waitRes == nil {
panic("nil wait")
}
// Log whether the task was successful or not.
r.restartTracker.SetWaitResult(waitRes)
r.setState(structs.TaskStateDead, r.waitErrorToEvent(waitRes))
if !waitRes.Successful() {
r.logger.Printf("[INFO] client: task %q for alloc %q failed: %v", r.task.Name, r.alloc.ID, waitRes)
} else {
r.logger.Printf("[INFO] client: task %q for alloc %q completed successfully", r.task.Name, r.alloc.ID)
}
break WAIT
case update := <-r.updateCh:
if err := r.handleUpdate(update); err != nil {
r.logger.Printf("[ERR] client: update to task %q failed: %v", r.task.Name, err)
}
case <-r.destroyCh:
// Kill the task using an exponential backoff in-case of failures.
destroySuccess, err := r.handleDestroy()
if !destroySuccess {
// We couldn't successfully destroy the resource created.
r.logger.Printf("[ERR] client: failed to kill task %q. Resources may have been leaked: %v", r.task.Name, err)
}
// Store that the task has been destroyed and any associated error.
r.setState(structs.TaskStateDead, structs.NewTaskEvent(structs.TaskKilled).SetKillError(err))
r.consulService.Deregister(r.task, r.alloc)
return
}
}
RESTART:
state, when := r.restartTracker.GetState()
r.restartTracker.SetStartError(nil).SetWaitResult(nil)
switch state {
case structs.TaskNotRestarting, structs.TaskTerminated:
r.logger.Printf("[INFO] client: Not restarting task: %v for alloc: %v ", r.task.Name, r.alloc.ID)
if state == structs.TaskNotRestarting {
r.setState(structs.TaskStateDead, structs.NewTaskEvent(structs.TaskNotRestarting))
}
return
case structs.TaskRestarting:
r.logger.Printf("[INFO] client: Restarting task %q for alloc %q in %v", r.task.Name, r.alloc.ID, when)
r.setState(structs.TaskStatePending, structs.NewTaskEvent(structs.TaskRestarting).SetRestartDelay(when))
default:
r.logger.Printf("[ERR] client: restart tracker returned unknown state: %q", state)
return
}
// Sleep but watch for destroy events.
select {
case <-time.After(when):
case <-r.destroyCh:
}
// Destroyed while we were waiting to restart, so abort.
r.destroyLock.Lock()
destroyed := r.destroy
r.destroyLock.Unlock()
if destroyed {
r.logger.Printf("[DEBUG] client: Not restarting task: %v because it's destroyed by user", r.task.Name)
r.setState(structs.TaskStateDead, structs.NewTaskEvent(structs.TaskKilled))
return
}
// Clear the handle so a new driver will be created.
r.handleLock.Lock()
r.handle = nil
r.handleLock.Unlock()
}
}
func (r *TaskRunner) startTask() error {
// Create a driver
driver, err := r.createDriver()
if err != nil {
r.logger.Printf("[ERR] client: failed to create driver of task '%s' for alloc '%s': %v",
r.task.Name, r.alloc.ID, err)
return err
}
// Start the job
handle, err := driver.Start(r.ctx, r.task)
if err != nil {
r.logger.Printf("[ERR] client: failed to start task '%s' for alloc '%s': %v",
r.task.Name, r.alloc.ID, err)
return err
}
r.handleLock.Lock()
r.handle = handle
r.handleLock.Unlock()
return nil
}
// handleUpdate takes an updated allocation and updates internal state to
// reflect the new config for the task.
func (r *TaskRunner) handleUpdate(update *structs.Allocation) error {
// Extract the task group from the alloc.
tg := update.Job.LookupTaskGroup(update.TaskGroup)
if tg == nil {
return fmt.Errorf("alloc '%s' missing task group '%s'", update.ID, update.TaskGroup)
}
// Extract the task.
var updatedTask *structs.Task
for _, t := range tg.Tasks {
if t.Name == r.task.Name {
updatedTask = t
}
}
if updatedTask == nil {
return fmt.Errorf("task group %q doesn't contain task %q", tg.Name, r.task.Name)
}
// Merge in the task resources
updatedTask.Resources = update.TaskResources[updatedTask.Name]
// Update will update resources and store the new kill timeout.
var mErr multierror.Error
r.handleLock.Lock()
if r.handle != nil {
if err := r.handle.Update(updatedTask); err != nil {
mErr.Errors = append(mErr.Errors, fmt.Errorf("updating task resources failed: %v", err))
}
}
r.handleLock.Unlock()
// Update the restart policy.
if r.restartTracker != nil {
r.restartTracker.SetPolicy(tg.RestartPolicy)
}
// Hash services returns the hash of the task's services
hashServices := func(task *structs.Task) uint64 {
h, err := hashstructure.Hash(task.Services, nil)
if err != nil {
mErr.Errors = append(mErr.Errors, fmt.Errorf("hashing services failed %#v: %v", task.Services, err))
}
return h
}
// Re-register the task to consul if any of the services have changed.
if hashServices(updatedTask) != hashServices(r.task) {
if err := r.consulService.Register(updatedTask, update); err != nil {
mErr.Errors = append(mErr.Errors, fmt.Errorf("updating services with consul failed: %v", err))
}
}
// Store the updated alloc.
r.alloc = update
r.task = updatedTask
return mErr.ErrorOrNil()
}
// handleDestroy kills the task handle. In the case that killing fails,
// handleDestroy will retry with an exponential backoff and will give up at a
// given limit. It returns whether the task was destroyed and the error
// associated with the last kill attempt.
func (r *TaskRunner) handleDestroy() (destroyed bool, err error) {
// Cap the number of times we attempt to kill the task.
for i := 0; i < killFailureLimit; i++ {
if err = r.handle.Kill(); err != nil {
// Calculate the new backoff
backoff := (1 << (2 * uint64(i))) * killBackoffBaseline
if backoff > killBackoffLimit {
backoff = killBackoffLimit
}
r.logger.Printf("[ERR] client: failed to kill task '%s' for alloc %q. Retrying in %v: %v",
r.task.Name, r.alloc.ID, backoff, err)
time.Sleep(time.Duration(backoff))
} else {
// Kill was successful
return true, nil
}
}
return
}
// Helper function for converting a WaitResult into a TaskTerminated event.
func (r *TaskRunner) waitErrorToEvent(res *cstructs.WaitResult) *structs.TaskEvent {
return structs.NewTaskEvent(structs.TaskTerminated).
SetExitCode(res.ExitCode).
SetSignal(res.Signal).
SetExitMessage(res.Err)
}
// Update is used to update the task of the context
func (r *TaskRunner) Update(update *structs.Allocation) {
select {
case r.updateCh <- update:
default:
r.logger.Printf("[ERR] client: dropping task update '%s' (alloc '%s')",
r.task.Name, r.alloc.ID)
}
}
// Destroy is used to indicate that the task context should be destroyed
func (r *TaskRunner) Destroy() {
r.destroyLock.Lock()
defer r.destroyLock.Unlock()
if r.destroy {
return
}
r.destroy = true
close(r.destroyCh)
}