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task.go
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task.go
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package exec
import (
"context"
"fmt"
"sync"
u "github.com/araddon/gou"
"github.com/fuhongbo/qlbridge/plan"
"github.com/fuhongbo/qlbridge/schema"
)
const (
// ItemDefaultChannelSize default channel buffer for task's
ItemDefaultChannelSize = 50
)
// TaskBase Base executeable task that implements Task interface, embedded
// into other channel based task runners
type TaskBase struct {
sync.Mutex
Ctx *plan.Context
Name string
Handler MessageHandler
depth int
setup bool
closed bool
hasquit bool
msgInCh MessageChan
msgOutCh MessageChan
errCh ErrChan
sigCh SigChan // notify of quit/stop
errors []error
}
func NewTaskBase(ctx *plan.Context) *TaskBase {
if ctx.Context == nil {
ctx.Context = context.Background()
}
return &TaskBase{
// All Tasks Get output channels by default, but NOT input
msgOutCh: make(MessageChan, ItemDefaultChannelSize),
sigCh: make(SigChan, 1),
errCh: make(ErrChan, 10),
errors: make([]error, 0),
Ctx: ctx,
}
}
func (m *TaskBase) Children() []Task { return nil }
func (m *TaskBase) Setup(depth int) error {
m.depth = depth
m.setup = true
//u.Debugf("setup() %s %T in:%p out:%p", m.TaskType, m, m.msgInCh, m.msgOutCh)
return nil
}
func (m *TaskBase) Add(task Task) error { return fmt.Errorf("This is not a list-type task %T", m) }
func (m *TaskBase) AddPlan(task plan.Task) error {
return fmt.Errorf("This is not a list-type task %T", m)
}
func (m *TaskBase) MessageIn() MessageChan { return m.msgInCh }
func (m *TaskBase) MessageOut() MessageChan { return m.msgOutCh }
func (m *TaskBase) MessageInSet(ch MessageChan) { m.msgInCh = ch }
func (m *TaskBase) MessageOutSet(ch MessageChan) { m.msgOutCh = ch }
func (m *TaskBase) ErrChan() ErrChan { return m.errCh }
func (m *TaskBase) SigChan() SigChan { return m.sigCh }
func (m *TaskBase) Quit() {
if m.hasquit {
return
}
defer func() {
if r := recover(); r != nil {
u.Errorf("Error on closing sigchannel %v", r)
}
}()
m.hasquit = true
close(m.sigCh)
}
func (m *TaskBase) Close() error {
//u.Debugf("%p start Close()", m)
defer func() {
if r := recover(); r != nil {
u.Errorf("panic in close %v", r)
}
}()
m.Lock()
if m.closed {
m.Unlock()
return nil
}
m.closed = true
m.Unlock()
//u.Debugf("%p finished Close()", m)
close(m.sigCh)
return nil
}
func (m *TaskBase) CloseFinal() error { return nil }
func MakeHandler(task TaskRunner) MessageHandler {
out := task.MessageOut()
return func(ctx *plan.Context, msg schema.Message) bool {
select {
case out <- msg:
return true
case <-task.SigChan():
return false
}
}
}
func (m *TaskBase) Run() error {
defer m.Ctx.Recover() // Our context can recover panics, save error msg
defer func() {
close(m.msgOutCh) // closing output channels is the signal to stop
//u.Debugf("close taskbase: ch:%p %v", m.msgOutCh, m.Type())
}()
//u.Debugf("TaskBase: %T inchan", m)
if m.Handler == nil {
u.Warnf("returning, no handler %T", m)
return fmt.Errorf("Must have a handler to run base runner")
}
ok := true
var err error
var msg schema.Message
msgLoop:
for ok {
// Either of the SigQuit, or error channel will
// cause breaking out of message channels below
select {
case err = <-m.errCh:
//m.errors = append(m.errors, err)
break msgLoop
case <-m.sigCh: // Signal, ie quit etc
//u.Debugf("got taskbase signal")
break msgLoop
default:
}
//
select {
case msg, ok = <-m.msgInCh:
if ok {
//u.Debugf("sending to handler: %T %+v", msg, msg)
m.Handler(m.Ctx, msg)
} else {
//u.Debugf("msg in closed shutting down")
break msgLoop
}
case <-m.sigCh:
break msgLoop
}
}
//u.Warnf("exiting")
return err
}
// On Task stepper we don't Run it, rather use a
// Next() explicit call from end user
type TaskStepper struct {
*TaskBase
}
func NewTaskStepper(ctx *plan.Context) *TaskStepper {
t := NewTaskBase(ctx)
return &TaskStepper{t}
}
func (m *TaskStepper) Run() error {
defer m.Ctx.Recover() // Our context can recover panics, save error msg
defer close(m.msgOutCh) // closing output channels is the signal to stop
for {
select {
case <-m.sigCh:
return nil
}
}
}