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scheduler.go
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scheduler.go
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package main
import (
"context"
"encoding/json"
"fmt"
"github.com/sirupsen/logrus"
"github.com/terorie/od-database-crawler/fasturl"
"os"
"path"
"sync"
"sync/atomic"
"time"
)
var activeTasksLock sync.Mutex
var activeTasks = make(map[uint64]bool)
var numActiveTasks int32
var totalQueued int64
func Schedule(c context.Context, remotes <-chan *OD) {
go Stats(c)
for remote := range remotes {
logrus.WithField("url", remote.BaseUri.String()).
Info("Starting crawler")
// Collect results
results := make(chan File)
remote.WCtx.OD = remote
// Get queue path
queuePath := path.Join("queue", fmt.Sprintf("%d", remote.Task.WebsiteId))
// Delete existing queue
if err := os.RemoveAll(queuePath);
err != nil { panic(err) }
// Start new queue
var err error
remote.WCtx.Queue, err = OpenQueue(queuePath)
if err != nil { panic(err) }
// Spawn workers
for i := 0; i < config.Workers; i++ {
go remote.WCtx.Worker(results)
}
// Enqueue initial job
atomic.AddInt32(&numActiveTasks, 1)
remote.WCtx.queueJob(Job{
Uri: remote.BaseUri,
UriStr: remote.BaseUri.String(),
Fails: 0,
})
// Upload result when ready
go remote.Watch(results)
// Sleep if max number of tasks are active
for atomic.LoadInt32(&numActiveTasks) > config.Tasks {
select {
case <-c.Done():
return
case <-time.After(time.Second):
continue
}
}
}
}
func ScheduleTask(remotes chan<- *OD, t *Task, u *fasturl.URL) {
if !t.register() {
return
}
globalWait.Add(1)
now := time.Now()
od := &OD {
Task: *t,
BaseUri: *u,
Result: TaskResult {
WebsiteId: t.WebsiteId,
StartTime: now,
StartTimeUnix: now.Unix(),
},
}
remotes <- od
}
func (t *Task) register() bool {
activeTasksLock.Lock()
defer activeTasksLock.Unlock()
if _, known := activeTasks[t.WebsiteId]; known {
return false
} else {
activeTasks[t.WebsiteId] = true
return true
}
}
func (t *Task) unregister() {
activeTasksLock.Lock()
delete(activeTasks, t.WebsiteId)
activeTasksLock.Unlock()
}
func (o *OD) Watch(results chan File) {
// Mark job as completely done
defer globalWait.Done()
defer o.Task.unregister()
filePath := path.Join("crawled", fmt.Sprintf("%d.json", o.Task.WebsiteId))
// Open crawl results file
f, err := os.OpenFile(
filePath,
os.O_CREATE | os.O_RDWR | os.O_TRUNC,
0644,
)
if err != nil {
logrus.WithError(err).
Error("Failed saving crawl results")
return
}
defer f.Close()
defer os.Remove(filePath)
// Listen for exit code of Collect()
collectErrC := make(chan error)
// Block until all results are written
// (closes results channel)
o.handleCollect(results, f, collectErrC)
// Exit code of Collect()
err = <-collectErrC
close(collectErrC)
if err != nil {
logrus.WithError(err).
Error("Failed saving crawl results")
return
}
// Upload results
err = PushResult(&o.Result, f)
if err != nil {
logrus.WithError(err).
Error("Failed uploading crawl results")
return
}
}
func (o *OD) handleCollect(results chan File, f *os.File, collectErrC chan error) {
// Begin collecting results
go o.Task.Collect(results, f, collectErrC)
defer close(results)
// Wait for all jobs on remote to finish
o.Wait.Wait()
// Close queue
if err := o.WCtx.Queue.Close(); err != nil {
panic(err)
}
atomic.AddInt32(&numActiveTasks, -1)
// Log finish
logrus.WithFields(logrus.Fields{
"id": o.Task.WebsiteId,
"url": o.BaseUri.String(),
"duration": time.Since(o.Result.StartTime),
}).Info("Crawler finished")
// Set status code
now := time.Now()
o.Result.EndTimeUnix = now.Unix()
fileCount := atomic.LoadUint64(&o.Result.FileCount)
if fileCount == 0 {
errorCount := atomic.LoadUint64(&o.Result.ErrorCount)
if errorCount == 0 {
o.Result.StatusCode = "empty"
} else {
o.Result.StatusCode = "directory listing failed"
}
} else {
o.Result.StatusCode = "success"
}
}
func (t *Task) Collect(results chan File, f *os.File, errC chan<- error) {
err := t.collect(results, f)
if err != nil {
logrus.WithError(err).
Error("Failed saving crawl results")
}
errC <- err
}
func (t *Task) collect(results chan File, f *os.File) error {
for result := range results {
result.Path = fasturl.PathUnescape(result.Path)
result.Name = fasturl.PathUnescape(result.Name)
resJson, err := json.Marshal(result)
if err != nil { panic(err) }
_, err = f.Write(resJson)
if err != nil { return err }
_, err = f.Write([]byte{'\n'})
if err != nil { return err }
}
return nil
}