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spawner.go
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spawner.go
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package ik
import (
"fmt"
"reflect"
"sync"
)
type descriptorListHead struct {
next *spawneeDescriptor
prev *spawneeDescriptor
}
type descriptorList struct {
count int
first *spawneeDescriptor
last *spawneeDescriptor
}
type spawneeDescriptor struct {
head_alive descriptorListHead
head_dead descriptorListHead
id int
spawnee Spawnee
exitStatus error
shutdownRequested bool
mtx sync.Mutex
cond *sync.Cond
}
type SpawneeStatus struct {
Id int
Spawnee Spawnee
ExitStatus error
}
type dispatchReturnValue struct {
b bool
s []Spawnee
e error
ss []SpawneeStatus
}
type dispatch struct {
fn func(Spawnee, chan dispatchReturnValue)
spawnee Spawnee
retval chan dispatchReturnValue
}
const (
Spawned = 1
Stopped = 2
)
type ContinueType struct{}
type Panicked struct {
panic interface{}
}
func (_ *ContinueType) Error() string { return "" }
func typeName(type_ reflect.Type) string {
if type_.Kind() == reflect.Ptr {
return "*" + typeName(type_.Elem())
} else {
return type_.Name()
}
}
func (panicked *Panicked) Error() string {
switch panic_ := panicked.panic.(type) {
case string:
return panic_
case error:
return fmt.Sprintf("(%s) %s", typeName(reflect.TypeOf(panic_)), panic_.Error())
default:
type_ := reflect.TypeOf(panic_)
method, ok := type_.MethodByName("String")
if ok && method.Type.NumIn() == 1 {
result := method.Func.Call([]reflect.Value{reflect.ValueOf(panic_)})
if len(result) == 1 && result[0].Type().Kind() == reflect.String {
return fmt.Sprintf("(%s) %s", typeName(type_), result[0].String())
}
}
return fmt.Sprintf("(%s)", typeName(type_))
}
}
var Continue = &ContinueType{}
type NotFoundType struct{}
func (_ *NotFoundType) Error() string { return "not found" }
var NotFound = &NotFoundType{}
type spawnerEvent struct {
t int
spawnee Spawnee
}
type Spawner struct {
alives descriptorList
deads descriptorList
m map[Spawnee]*spawneeDescriptor
c chan dispatch
mtx sync.Mutex
cond *sync.Cond
lastEvent *spawnerEvent
}
func newDescriptor(spawnee Spawnee, id int) *spawneeDescriptor {
retval := &spawneeDescriptor{
head_alive: descriptorListHead{nil, nil},
head_dead: descriptorListHead{nil, nil},
id: id,
spawnee: spawnee,
exitStatus: Continue,
shutdownRequested: false,
mtx: sync.Mutex{},
cond: nil,
}
retval.cond = sync.NewCond(&retval.mtx)
return retval
}
func (spawner *Spawner) spawn(spawnee Spawnee, retval chan dispatchReturnValue) {
go func() {
descriptor := newDescriptor(spawnee, len(spawner.m)+1)
func() {
spawner.mtx.Lock()
defer spawner.mtx.Unlock()
if spawner.alives.last != nil {
spawner.alives.last.head_alive.next = descriptor
descriptor.head_alive.prev = spawner.alives.last
}
if spawner.alives.first == nil {
spawner.alives.first = descriptor
}
spawner.alives.last = descriptor
spawner.alives.count += 1
spawner.m[spawnee] = descriptor
// notify the event
spawner.lastEvent = &spawnerEvent{
t: Spawned,
spawnee: spawnee,
}
spawner.cond.Broadcast()
retval <- dispatchReturnValue{true, nil, nil, nil}
}()
var exitStatus error = nil
func() {
defer func() {
r := recover()
if r != nil {
exitStatus = &Panicked{r}
}
}()
exitStatus = Continue
for exitStatus == Continue {
exitStatus = descriptor.spawnee.Run()
}
}()
func() {
spawner.mtx.Lock()
defer spawner.mtx.Unlock()
descriptor.exitStatus = exitStatus
// remove from alive list
if descriptor.head_alive.prev != nil {
descriptor.head_alive.prev.head_alive.next = descriptor.head_alive.next
} else {
spawner.alives.first = descriptor.head_alive.next
}
if descriptor.head_alive.next != nil {
descriptor.head_alive.next.head_alive.prev = descriptor.head_alive.prev
} else {
spawner.alives.last = descriptor.head_alive.prev
}
spawner.alives.count -= 1
// append to dead list
if spawner.deads.last != nil {
spawner.deads.last.head_dead.next = descriptor
descriptor.head_dead.prev = spawner.deads.last
}
if spawner.deads.first == nil {
spawner.deads.first = descriptor
}
spawner.deads.last = descriptor
spawner.deads.count += 1
// notify the event
spawner.lastEvent = &spawnerEvent{
t: Stopped,
spawnee: spawnee,
}
spawner.cond.Broadcast()
descriptor.cond.Broadcast()
}()
}()
}
func (spawner *Spawner) kill(spawnee Spawnee, retval chan dispatchReturnValue) {
spawner.mtx.Lock()
descriptor, ok := spawner.m[spawnee]
spawner.mtx.Unlock()
if ok && descriptor.exitStatus != Continue {
descriptor.shutdownRequested = true
err := spawnee.Shutdown()
retval <- dispatchReturnValue{true, nil, err, nil}
} else {
retval <- dispatchReturnValue{false, nil, nil, nil}
}
}
func (spawner *Spawner) getStatus(spawnee Spawnee, retval chan dispatchReturnValue) {
spawner.mtx.Lock()
defer spawner.mtx.Unlock()
descriptor, ok := spawner.m[spawnee]
if ok {
retval <- dispatchReturnValue{false, nil, descriptor.exitStatus, nil}
} else {
retval <- dispatchReturnValue{false, nil, nil, nil}
}
}
func (spawner *Spawner) getRunningSpawnees(_ Spawnee, retval chan dispatchReturnValue) {
spawner.mtx.Lock()
defer spawner.mtx.Unlock()
spawnees := make([]Spawnee, spawner.alives.count)
descriptor := spawner.alives.first
i := 0
for descriptor != nil {
spawnees[i] = descriptor.spawnee
descriptor = descriptor.head_alive.next
i += 1
}
retval <- dispatchReturnValue{false, spawnees, nil, nil}
}
func (spawner *Spawner) getStoppedSpawnees(_ Spawnee, retval chan dispatchReturnValue) {
spawner.mtx.Lock()
defer spawner.mtx.Unlock()
spawnees := make([]Spawnee, spawner.deads.count)
descriptor := spawner.deads.first
i := 0
for descriptor != nil {
spawnees[i] = descriptor.spawnee
descriptor = descriptor.head_dead.next
i += 1
}
retval <- dispatchReturnValue{false, spawnees, nil, nil}
}
func (spawner *Spawner) getSpawneeStatuses(_ Spawnee, retval chan dispatchReturnValue) {
spawner.mtx.Lock()
defer spawner.mtx.Unlock()
spawneeStatuses := make([]SpawneeStatus, len(spawner.m))
i := 0
for spawnee, descriptor := range spawner.m {
spawneeStatuses[i] = SpawneeStatus{Id: descriptor.id, Spawnee: spawnee, ExitStatus: descriptor.exitStatus}
i += 1
}
retval <- dispatchReturnValue{false, nil, nil, spawneeStatuses}
}
func (spawner *Spawner) Spawn(spawnee Spawnee) error {
retval := make(chan dispatchReturnValue)
spawner.c <- dispatch{spawner.spawn, spawnee, retval}
retval_ := <-retval
return retval_.e
}
func (spawner *Spawner) Kill(spawnee Spawnee) (bool, error) {
retval := make(chan dispatchReturnValue)
spawner.c <- dispatch{spawner.kill, spawnee, retval}
retval_ := <-retval
return retval_.b, retval_.e
}
func (spawner *Spawner) GetStatus(spawnee Spawnee) error {
retval := make(chan dispatchReturnValue)
spawner.c <- dispatch{spawner.getStatus, spawnee, retval}
retval_ := <-retval
return retval_.e
}
func (spawner *Spawner) GetRunningSpawnees() ([]Spawnee, error) {
retval := make(chan dispatchReturnValue)
spawner.c <- dispatch{spawner.getRunningSpawnees, nil, retval}
retval_ := <-retval
return retval_.s, retval_.e
}
func (spawner *Spawner) GetStoppedSpawnees() ([]Spawnee, error) {
retval := make(chan dispatchReturnValue)
spawner.c <- dispatch{spawner.getStoppedSpawnees, nil, retval}
retval_ := <-retval
return retval_.s, retval_.e
}
func (spawner *Spawner) GetSpawneeStatuses() ([]SpawneeStatus, error) {
retval := make(chan dispatchReturnValue)
spawner.c <- dispatch{spawner.getSpawneeStatuses, nil, retval}
retval_ := <-retval
return retval_.ss, retval_.e
}
func (spawner *Spawner) Poll(spawnee Spawnee) error {
descriptor, ok := spawner.m[spawnee]
if !ok {
return NotFound
}
if func() bool {
spawner.mtx.Lock()
defer spawner.mtx.Unlock()
if descriptor.exitStatus != Continue {
return true
}
return false
}() {
return nil
}
defer descriptor.mtx.Unlock()
descriptor.mtx.Lock()
descriptor.cond.Wait()
return nil
}
func (spawner *Spawner) PollMultiple(spawnees []Spawnee) error {
spawnees_ := make(map[Spawnee]bool)
for _, spawnee := range spawnees {
spawnees_[spawnee] = true
}
count := len(spawnees_)
for count > 0 {
spawner.mtx.Lock()
spawner.cond.Wait()
lastEvent := spawner.lastEvent
spawner.mtx.Unlock()
if lastEvent.t == Stopped {
spawnee := lastEvent.spawnee
if alive, ok := spawnees_[spawnee]; alive && ok {
spawnees_[spawnee] = false
count -= 1
}
}
}
return nil
}
func NewSpawner() *Spawner {
c := make(chan dispatch)
// launch the supervisor
go func() {
for {
select {
case disp := <-c:
disp.fn(disp.spawnee, disp.retval)
}
}
}()
spawner := &Spawner{
alives: descriptorList{0, nil, nil},
deads: descriptorList{0, nil, nil},
m: make(map[Spawnee]*spawneeDescriptor),
c: c,
mtx: sync.Mutex{},
cond: nil,
lastEvent: nil,
}
spawner.cond = sync.NewCond(&spawner.mtx)
return spawner
}