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package tasks
import (
"bufio"
"fmt"
"io"
"os/exec"
"sync"
"time"
"github.com/sirupsen/logrus"
)
type Task struct {
stop chan struct{}
stopped bool
stopMutex sync.Mutex
notifyStopped chan struct{}
Log *logrus.Entry
f func(chan struct{}) error
}
type ViewBufferManager struct {
writer io.Writer
waitingTask *Task
currentTask *Task
waitingMutex sync.Mutex
taskIDMutex sync.Mutex
Log *logrus.Entry
newTaskId int
readLines chan int
// beforeStart is the function that is called before starting a new task
beforeStart func()
refreshView func()
}
func NewViewBufferManager(log *logrus.Entry, writer io.Writer, beforeStart func(), refreshView func()) *ViewBufferManager {
return &ViewBufferManager{Log: log, writer: writer, beforeStart: beforeStart, refreshView: refreshView, readLines: make(chan int, 1024)}
}
func (m *ViewBufferManager) ReadLines(n int) {
go func() {
m.readLines <- n
}()
}
func (m *ViewBufferManager) NewCmdTask(cmd *exec.Cmd, linesToRead int) func(chan struct{}) error {
return func(stop chan struct{}) error {
r, err := cmd.StdoutPipe()
if err != nil {
return err
}
cmd.Stderr = cmd.Stdout
if err := cmd.Start(); err != nil {
return err
}
go func() {
<-stop
if cmd.ProcessState == nil {
if err := kill(cmd); err != nil {
m.Log.Warn(err)
}
}
}()
// not sure if it's the right move to redefine this or not
m.readLines = make(chan int, 1024)
done := make(chan struct{})
go func() {
scanner := bufio.NewScanner(r)
scanner.Split(bufio.ScanLines)
loaded := false
go func() {
ticker := time.NewTicker(time.Millisecond * 100)
defer ticker.Stop()
select {
case <-ticker.C:
if !loaded {
m.beforeStart()
m.writer.Write([]byte("loading..."))
m.refreshView()
}
case <-stop:
return
}
}()
outer:
for {
select {
case linesToRead := <-m.readLines:
for i := 0; i < linesToRead; i++ {
ok := scanner.Scan()
if !loaded {
m.beforeStart()
loaded = true
}
select {
case <-stop:
break outer
default:
}
if !ok {
m.refreshView()
break outer
}
m.writer.Write(append(scanner.Bytes(), []byte("\n")...))
}
m.refreshView()
case <-stop:
break outer
}
}
if err := cmd.Wait(); err != nil {
m.Log.Warn(err)
}
close(done)
}()
m.readLines <- linesToRead
<-done
return nil
}
}
// Close closes the task manager, killing whatever task may currently be running
func (t *ViewBufferManager) Close() {
if t.currentTask == nil {
return
}
c := make(chan struct{}, 1)
go func() {
t.currentTask.Stop()
c <- struct{}{}
}()
select {
case <-c:
return
case <-time.After(3 * time.Second):
fmt.Println("cannot kill child process")
}
}
// different kinds of tasks:
// 1) command based, where the manager can be asked to read more lines, but the command can be killed
// 2) string based, where the manager can also be asked to read more lines
func (m *ViewBufferManager) NewTask(f func(stop chan struct{}) error) error {
go func() {
m.taskIDMutex.Lock()
m.newTaskId++
taskID := m.newTaskId
m.Log.Infof("starting task %d", taskID)
m.taskIDMutex.Unlock()
m.waitingMutex.Lock()
defer m.waitingMutex.Unlock()
if taskID < m.newTaskId {
return
}
stop := make(chan struct{})
notifyStopped := make(chan struct{})
if m.currentTask != nil {
m.Log.Info("asking task to stop")
m.currentTask.Stop()
m.Log.Info("task stopped")
}
m.currentTask = &Task{
stop: stop,
notifyStopped: notifyStopped,
Log: m.Log,
f: f,
}
go func() {
if err := f(stop); err != nil {
m.Log.Error(err) // might need an onError callback
}
m.Log.Infof("returning from task %d", taskID)
close(notifyStopped)
}()
}()
return nil
}
func (t *Task) Stop() {
t.stopMutex.Lock()
defer t.stopMutex.Unlock()
if t.stopped {
return
}
close(t.stop)
t.Log.Info("closed stop channel, waiting for notifyStopped message")
<-t.notifyStopped
t.Log.Info("received notifystopped message")
t.stopped = true
return
}
// kill kills a process
func kill(cmd *exec.Cmd) error {
if cmd.Process == nil {
// somebody got to it before we were able to, poor bastard
return nil
}
return cmd.Process.Kill()
}
|