Beta task resuming

config.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"fmt"
 	"github.com/sirupsen/logrus"
+	"github.com/spf13/pflag"
 	"github.com/spf13/viper"
 	"io"
 	"os"
@@ -26,6 +27,8 @@ var config struct {
 	JobBufferSize int
 }
 
+var onlineMode bool
+
 const (
 	ConfServerUrl  = "server.url"
 	ConfToken      = "server.token"
@@ -43,6 +46,7 @@ const (
 	ConfDialTimeout = "crawl.dial_timeout"
 	ConfTimeout    = "crawl.timeout"
 	ConfJobBufferSize = "crawl.job_buffer"
+	ConfResume     = "crawl.resume"
 
 	ConfCrawlStats = "output.crawl_stats"
 	ConfAllocStats = "output.resource_stats"
@@ -54,8 +58,58 @@ const (
 func prepareConfig() {
 	pf := rootCmd.PersistentFlags()
 
-	bind := func(s string) {
+	pf.SortFlags = false
-		if err := viper.BindPFlag(s, pf.Lookup(s)); err != nil {
+	pf.StringVar(&configFile, "config", "", "Config file")
+	configFile = os.Getenv("OD_CONFIG")
+
+	pf.String(ConfServerUrl, "http://od-db.the-eye.eu/api", "OD-DB server URL")
+
+	pf.String(ConfToken, "", "OD-DB access token (env OD_SERVER_TOKEN)")
+
+	pf.Duration(ConfServerTimeout, 60 * time.Second, "OD-DB request timeout")
+
+	pf.Duration(ConfRecheck, 1 * time.Second, "OD-DB: Poll interval for new jobs")
+
+	pf.Duration(ConfCooldown, 30 * time.Second, "OD-DB: Time to wait after a server-side error")
+
+	pf.String(ConfChunkSize, "1 MB", "OD-DB: Result upload chunk size")
+
+	pf.Uint(ConfUploadRetries, 10, "OD-DB: Max upload retries")
+
+	pf.Duration(ConfUploadRetryInterval, 30 * time.Second, "OD-DB: Time to wait between upload retries")
+
+	pf.Uint(ConfTasks, 100, "Crawler: Max concurrent tasks")
+
+	pf.Uint(ConfWorkers, 4, "Crawler: Connections per server")
+
+	pf.Uint(ConfRetries, 5, "Crawler: Request retries")
+
+	pf.Duration(ConfDialTimeout, 10 * time.Second, "Crawler: Handshake timeout")
+
+	pf.Duration(ConfTimeout, 30 * time.Second, "Crawler: Request timeout")
+
+	pf.String(ConfUserAgent, "Mozilla/5.0 (X11; od-database-crawler) Gecko/20100101 Firefox/52.0", "Crawler: User-Agent")
+
+	pf.Uint(ConfJobBufferSize, 5000, "Crawler: Task queue cache size")
+
+	pf.Duration(ConfResume, 72 * time.Hour, "Crawler: Resume tasks not older than x")
+
+	pf.Duration(ConfCrawlStats, time.Second, "Log: Crawl stats interval")
+
+	pf.Duration(ConfAllocStats, 10 * time.Second, "Log: Resource stats interval")
+
+	pf.Bool(ConfVerbose, false, "Log: Print every listed dir")
+
+	pf.Bool(ConfPrintHTTP, false, "Log: Print HTTP client errors")
+
+	pf.String(ConfLogFile, "crawler.log", "Log file")
+
+	// Bind all flags to Viper
+	pf.VisitAll(func(flag *pflag.Flag) {
+		s := flag.Name
+		s = strings.TrimLeft(s, "-")
+
+		if err := viper.BindPFlag(s, flag); err != nil {
 			panic(err)
 		}
 		var envKey string
@@ -65,71 +119,7 @@ func prepareConfig() {
 		if err := viper.BindEnv(s, envKey); err != nil {
 			panic(err)
 		}
-	}
+	})
-
-	pf.SortFlags = false
-	pf.StringVar(&configFile, "config", "", "Config file")
-	configFile = os.Getenv("OD_CONFIG")
-
-	pf.String(ConfServerUrl, "http://od-db.the-eye.eu/api", "OD-DB server URL")
-	bind(ConfServerUrl)
-
-	pf.String(ConfToken, "", "OD-DB access token (env OD_SERVER_TOKEN)")
-	bind(ConfToken)
-
-	pf.Duration(ConfServerTimeout, 60 * time.Second, "OD-DB request timeout")
-	bind(ConfServerTimeout)
-
-	pf.Duration(ConfRecheck, 1 * time.Second, "OD-DB: Poll interval for new jobs")
-	bind(ConfRecheck)
-
-	pf.Duration(ConfCooldown, 30 * time.Second, "OD-DB: Time to wait after a server-side error")
-	bind(ConfCooldown)
-
-	pf.String(ConfChunkSize, "1 MB", "OD-DB: Result upload chunk size")
-	bind(ConfChunkSize)
-
-	pf.Uint(ConfUploadRetries, 10, "OD-DB: Max upload retries")
-	bind(ConfUploadRetries)
-
-	pf.Duration(ConfUploadRetryInterval, 30 * time.Second, "OD-DB: Time to wait between upload retries")
-	bind(ConfUploadRetryInterval)
-
-	pf.Uint(ConfTasks, 100, "Crawler: Max concurrent tasks")
-	bind(ConfTasks)
-
-	pf.Uint(ConfWorkers, 4, "Crawler: Connections per server")
-	bind(ConfWorkers)
-
-	pf.Uint(ConfRetries, 5, "Crawler: Request retries")
-	bind(ConfRetries)
-
-	pf.Duration(ConfDialTimeout, 10 * time.Second, "Crawler: Handshake timeout")
-	bind(ConfDialTimeout)
-
-	pf.Duration(ConfTimeout, 30 * time.Second, "Crawler: Request timeout")
-	bind(ConfTimeout)
-
-	pf.String(ConfUserAgent, "Mozilla/5.0 (X11; od-database-crawler) Gecko/20100101 Firefox/52.0", "Crawler: User-Agent")
-	bind(ConfUserAgent)
-
-	pf.Uint(ConfJobBufferSize, 5000, "Crawler: Task queue cache size")
-	bind(ConfJobBufferSize)
-
-	pf.Duration(ConfCrawlStats, time.Second, "Log: Crawl stats interval")
-	bind(ConfCrawlStats)
-
-	pf.Duration(ConfAllocStats, 10 * time.Second, "Log: Resource stats interval")
-	bind(ConfAllocStats)
-
-	pf.Bool(ConfVerbose, false, "Log: Print every listed dir")
-	bind(ConfVerbose)
-
-	pf.Bool(ConfPrintHTTP, false, "Log: Print HTTP client errors")
-	bind(ConfPrintHTTP)
-
-	pf.String(ConfLogFile, "crawler.log", "Log file")
-	bind(ConfLogFile)
 }
 
 func readConfig() {
@@ -157,6 +147,7 @@ func readConfig() {
 		}
 	}
 
+	if onlineMode {
 		config.ServerUrl = viper.GetString(ConfServerUrl)
 		if config.ServerUrl == "" {
 			configMissing(ConfServerUrl)
@@ -167,6 +158,7 @@ func readConfig() {
 		if config.Token == "" {
 			configMissing(ConfToken)
 		}
+	}
 
 	config.ServerTimeout = viper.GetDuration(ConfServerTimeout)
 

ds/redblackhash/redblack.go

@@ -15,7 +15,10 @@ package redblackhash
 
 import (
 	"bytes"
+	"encoding/binary"
+	"encoding/hex"
 	"fmt"
+	"io"
 	"sync"
 )
 
@@ -43,6 +46,13 @@ type Node struct {
 	Parent *Node
 }
 
+type nodeHeader struct {
+	Key   *Key
+	Color color
+}
+
+var o = binary.BigEndian
+
 func (k *Key) Compare(o *Key) int {
 	return bytes.Compare(k[:], o[:])
 }
@@ -233,7 +243,7 @@ func (tree *Tree) String() string {
 }
 
 func (node *Node) String() string {
-	return fmt.Sprintf("%v", node.Key)
+	return hex.EncodeToString(node.Key[:16]) + "..."
 }
 
 func output(node *Node, prefix string, isTail bool, str *string) {
@@ -481,6 +491,119 @@ func (tree *Tree) deleteCase6(node *Node) {
 	}
 }
 
+func (tree *Tree) Marshal(w io.Writer) (err error) {
+	tree.Lock()
+	defer tree.Unlock()
+
+	err = binary.Write(w, o, uint64(0x617979797979790A))
+	if err != nil { return err }
+
+	err = marshal(tree.Root, w)
+	if err != nil { return err }
+
+	err = binary.Write(w, o, uint64(0x6C6D616F6F6F6F0A))
+	if err != nil { return err }
+
+	return nil
+}
+
+func marshal(n *Node, w io.Writer) (err error) {
+	if n == nil {
+		err = binary.Write(w, o, uint64(0x796565656565740A))
+		return err
+	}
+
+	err = binary.Write(w, o, uint64(0xF09F85B1EFB88F0A))
+	if err != nil { return err }
+
+	_, err = w.Write(n.Key[:])
+	if err != nil { return err }
+
+	var colorI uint64
+	if n.color {
+		colorI = 0x7468652D6579657C
+	} else {
+		colorI = 0x6865782B7465727C
+	}
+
+	err = binary.Write(w, o, colorI)
+	if err != nil { return err }
+
+	err = marshal(n.Left, w)
+	if err != nil { return err }
+
+	err = marshal(n.Right, w)
+	if err != nil { return err }
+
+	return nil
+}
+
+func (tree *Tree) Unmarshal(r io.Reader) (err error) {
+	tree.Lock()
+	defer tree.Unlock()
+
+	var sof uint64
+	err = binary.Read(r, o, &sof)
+	if err != nil { return err }
+	if sof != 0x617979797979790A {
+		return fmt.Errorf("redblack: wrong format")
+	}
+
+	tree.Root, tree.size, err = unmarshal(r)
+	if err != nil { return err }
+
+	var eof uint64
+	err = binary.Read(r, o, &eof)
+	if err != nil { return err }
+	if eof != 0x6C6D616F6F6F6F0A {
+		return fmt.Errorf("redblack: end of file missing")
+	}
+
+	return nil
+}
+
+func unmarshal(r io.Reader) (n *Node, size int, err error) {
+	var head uint64
+	err = binary.Read(r, o, &head)
+	if err != nil { return nil, 0, err }
+
+	size = 1
+
+	switch head {
+	case 0x796565656565740A:
+		return nil, 0, nil
+	case 0xF09F85B1EFB88F0A:
+		n = new(Node)
+
+		_, err = io.ReadFull(r, n.Key[:])
+		if err != nil { return nil, 0, err }
+
+		var colorInt uint64
+		err = binary.Read(r, o, &colorInt)
+		if err != nil { return nil, 0, err }
+		switch colorInt {
+		case 0x7468652D6579657C:
+			n.color = true
+		case 0x6865782B7465727C:
+			n.color = false
+		default:
+			return nil, 0, fmt.Errorf("redblack: corrupt node color")
+		}
+	default:
+		return nil, 0, fmt.Errorf("redblack: corrupt node info")
+	}
+
+	var s2 int
+	n.Left, s2, err = unmarshal(r)
+	size += s2
+	if err != nil { return nil, 0, err }
+	n.Right, s2, err = unmarshal(r)
+	size += s2
+	if err != nil { return nil, 0, err }
+
+	return n, size, nil
+}
+
 func nodeColor(node *Node) color {
 	if node == nil {
 		return black

ds/redblackhash/redblack_test.go

@@ -0,0 +1,47 @@
+package redblackhash
+
+import (
+	"bytes"
+	"math/rand"
+	"testing"
+)
+
+func TestTree_Marshal(t *testing.T) {
+	var t1, t2 Tree
+
+	// Generate 1000 random values to insert
+	for i := 0; i < 1000; i++ {
+		var key Key
+		rand.Read(key[:])
+		t1.Put(&key)
+	}
+
+	// Marshal tree
+	var wr bytes.Buffer
+	err := t1.Marshal(&wr)
+	if err != nil {
+		t.Error(err)
+		t.FailNow()
+	}
+
+	buf := wr.Bytes()
+	rd := bytes.NewBuffer(buf)
+
+	// Unmarshal tree
+	err = t2.Unmarshal(rd)
+	if err != nil {
+		t.Error(err)
+		t.FailNow()
+	}
+
+	if !compare(t1.Root, t2.Root) {
+		t.Error("trees are not equal")
+		t.FailNow()
+	}
+}
+
+func compare(n1, n2 *Node) bool {
+	return n1.Key.Compare(&n2.Key) == 0 &&
+		(n1.Left == nil || compare(n1.Left, n2.Left)) &&
+		(n1.Right == nil || compare(n1.Right, n2.Right))
+}

main.go

@@ -8,6 +8,7 @@ import (
 	"github.com/spf13/viper"
 	"github.com/terorie/od-database-crawler/fasturl"
 	"os"
+	"os/signal"
 	"strings"
 	"sync/atomic"
 	"time"
@@ -61,8 +62,6 @@ func preRun(cmd *cobra.Command, args []string) error {
 	if err := os.MkdirAll("queue", 0755);
 		err != nil { panic(err) }
 
-	readConfig()
-
 	return nil
 }
 
@@ -75,25 +74,32 @@ func main() {
 }
 
 func cmdBase(_ *cobra.Command, _ []string) {
-	// TODO Graceful shutdown
+	onlineMode = true
-	appCtx := context.Background()
+	readConfig()
-	forceCtx := context.Background()
+
+	appCtx, soft := context.WithCancel(context.Background())
+	forceCtx, hard := context.WithCancel(context.Background())
+	go hardShutdown(forceCtx)
+	go listenCtrlC(soft, hard)
 
 	inRemotes := make(chan *OD)
-	go Schedule(forceCtx, inRemotes)
+	go LoadResumeTasks(inRemotes)
+	go Schedule(appCtx, inRemotes)
 
 	ticker := time.NewTicker(config.Recheck)
 	defer ticker.Stop()
 	for {
 		select {
 		case <-appCtx.Done():
-			return
+			goto shutdown
 		case <-ticker.C:
 			t, err := FetchTask()
 			if err != nil {
 				logrus.WithError(err).
 					Error("Failed to get new task")
-				time.Sleep(viper.GetDuration(ConfCooldown))
+				if !sleep(viper.GetDuration(ConfCooldown), appCtx) {
+					goto shutdown
+				}
 				continue
 			}
 			if t == nil {
@@ -126,9 +132,15 @@ func cmdBase(_ *cobra.Command, _ []string) {
 			ScheduleTask(inRemotes, t, &baseUri)
 		}
 	}
+
+	shutdown:
+	globalWait.Wait()
 }
 
 func cmdCrawler(_ *cobra.Command, args []string) error {
+	onlineMode = false
+	readConfig()
+
 	arg := args[0]
 	// https://github.com/golang/go/issues/19779
 	if !strings.Contains(arg, "://") {
@@ -161,3 +173,30 @@ func cmdCrawler(_ *cobra.Command, args []string) error {
 
 	return nil
 }
+
+func listenCtrlC(soft, hard context.CancelFunc) {
+	c := make(chan os.Signal)
+	signal.Notify(c, os.Interrupt)
+
+	<-c
+	logrus.Info(">>> Shutting down crawler... <<<")
+	soft()
+
+	<-c
+	logrus.Warning(">>> Force shutdown! <<<")
+	hard()
+}
+
+func hardShutdown(c context.Context) {
+	<-c.Done()
+	os.Exit(1)
+}
+
+func sleep(d time.Duration, c context.Context) bool {
+	select {
+	case <-time.After(d):
+		return true
+	case <-c.Done():
+		return false
+	}
+}

model.go

@@ -3,7 +3,6 @@ package main
 import (
 	"github.com/terorie/od-database-crawler/ds/redblackhash"
 	"github.com/terorie/od-database-crawler/fasturl"
-	"sync"
 	"time"
 )
 
@@ -32,12 +31,19 @@ type Job struct {
 type OD struct {
 	Task       Task
 	Result     TaskResult
-	Wait    sync.WaitGroup
+	InProgress int64
 	BaseUri    fasturl.URL
 	WCtx       WorkerContext
 	Scanned    redblackhash.Tree
 }
 
+type PausedOD struct {
+	Task       *Task
+	Result     *TaskResult
+	BaseUri    *fasturl.URL
+	InProgress int64
+}
+
 type File struct {
 	Name  string `json:"name"`
 	Size  int64  `json:"size"`

resume.go

@@ -0,0 +1,270 @@
+package main
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/gob"
+	"fmt"
+	"github.com/beeker1121/goque"
+	"github.com/sirupsen/logrus"
+	"github.com/spf13/viper"
+	"io"
+	"os"
+	"path/filepath"
+	"strconv"
+	"sync/atomic"
+	"time"
+)
+
+func init() {
+	gob.Register(&PausedOD{})
+}
+
+func LoadResumeTasks(inRemotes chan<- *OD) {
+	resumed, err := ResumeTasks()
+	if err != nil {
+		logrus.WithError(err).
+			Error("Failed to resume queued tasks. " +
+				"/queue is probably corrupt")
+		err = nil
+	}
+
+	for _, remote := range resumed {
+		inRemotes <- remote
+	}
+}
+
+func ResumeTasks() (tasks []*OD, err error) {
+	// Get files in /queue
+	var queueF *os.File
+	var entries []os.FileInfo
+	queueF, err = os.Open("queue")
+	if err != nil { return nil, err }
+	defer queueF.Close()
+	entries, err = queueF.Readdir(-1)
+	if err != nil { return nil, err }
+
+	resumeDur := viper.GetDuration(ConfResume)
+
+	for _, entry := range entries {
+		if !entry.IsDir() { continue }
+
+		// Check if name is a number
+		var id uint64
+		if id, err = strconv.ParseUint(entry.Name(), 10, 64); err != nil {
+			continue
+		}
+
+		// Too old to be resumed
+		timeDelta := time.Since(entry.ModTime())
+		if resumeDur >= 0 && timeDelta > resumeDur {
+			removeOldQueue(id)
+			continue
+		}
+
+		// Load queue
+		var od *OD
+		if od, err = resumeQueue(id); err != nil {
+			logrus.WithError(err).
+				WithField("id", id).
+				Warning("Failed to load paused task")
+			continue
+		} else if od == nil {
+			removeOldQueue(id)
+			continue
+		}
+
+		tasks = append(tasks, od)
+	}
+
+	return tasks, nil
+}
+
+func SaveTask(od *OD) (err error) {
+	dir := filepath.Join("queue",
+		strconv.FormatUint(od.Task.WebsiteId, 10))
+
+	fPath := filepath.Join(dir, "PAUSED")
+
+	err = os.Mkdir(dir, 0777)
+	if err != nil { return err }
+
+	// Open pause file
+	pausedF, err := os.OpenFile(fPath, os.O_CREATE | os.O_WRONLY | os.O_TRUNC, 0666)
+	if err != nil { return err }
+	defer pausedF.Close()
+
+	err = writePauseFile(od, pausedF)
+	if err != nil { return err }
+
+	return nil
+}
+
+func resumeQueue(id uint64) (od *OD, err error) {
+	logrus.WithField("id", id).
+		Info("Found unfinished")
+
+	fPath := filepath.Join("queue", strconv.FormatUint(id, 10))
+
+	// Try to find pause file
+	pausedF, err := os.Open(filepath.Join(fPath, "PAUSED"))
+	if os.IsNotExist(err) {
+		// No PAUSED file => not paused
+		// not paused => no error
+		return nil, nil
+	} else if err != nil {
+		return nil, err
+	}
+	defer pausedF.Close()
+
+	od = new(OD)
+	od.WCtx.OD = od
+
+	err = readPauseFile(od, pausedF)
+	if err != nil { return nil, err }
+
+	// Open queue
+	bq, err := OpenQueue(fPath)
+	if err != nil { return nil, err }
+
+	od.WCtx.Queue = bq
+
+	logrus.WithField("id", id).
+		Info("Resuming task")
+
+	return od, nil
+}
+
+func removeOldQueue(id uint64) {
+	if id == 0 {
+		// TODO Make custom crawl less of an ugly hack
+		return
+	}
+
+	logrus.WithField("id", id).
+		Warning("Deleting & returning old task")
+
+	name := strconv.FormatUint(id, 10)
+
+	fPath := filepath.Join("queue", name)
+
+	// Acquire old queue
+	q, err := goque.OpenQueue(fPath)
+	if err != nil {
+		// Queue lock exists, don't delete
+		logrus.WithField("err", err).
+			WithField("path", fPath).
+			Error("Failed to acquire old task")
+		return
+	}
+
+	// Delete old queue from disk
+	err = q.Drop()
+	if err != nil {
+		// Queue lock exists, don't delete
+		logrus.WithField("err", err).
+			WithField("path", fPath).
+			Error("Failed to delete old task")
+		return
+	}
+
+	// Delete old crawl result from disk
+	_ = os.Remove(filepath.Join("crawled", name + ".json"))
+
+	// Return task to server
+	if err := CancelTask(id); err != nil {
+		// Queue lock exists, don't delete
+		logrus.WithField("err", err).
+			WithField("id", id).
+			Warning("Failed to return unfinished task to server")
+		return
+	}
+}
+
+func writePauseFile(od *OD, w io.Writer) (err error) {
+	// Write pause file version
+	_, err = w.Write([]byte("ODPAUSE-"))
+	if err != nil { return err }
+
+	// Create save state
+	paused := PausedOD {
+		Task:       &od.Task,
+		Result:     &od.Result,
+		BaseUri:    &od.BaseUri,
+		InProgress: atomic.LoadInt64(&od.InProgress),
+	}
+
+	// Prepare pause settings
+	var b bytes.Buffer
+	pauseEnc := gob.NewEncoder(&b)
+	err = pauseEnc.Encode(&paused)
+	if err != nil { return err }
+
+	// Write length of pause settings
+	err = binary.Write(w, binary.LittleEndian, uint64(b.Len()))
+	if err != nil { return err }
+
+	// Write pause settings
+	_, err = w.Write(b.Bytes())
+	if err != nil { return err }
+
+	// Write pause scan state
+	err = od.Scanned.Marshal(w)
+	if err != nil { return err }
+
+	// Save mark
+	_, err = w.Write([]byte("--------"))
+	if err != nil { return err }
+	
+	return nil
+}
+
+func readPauseFile(od *OD, r io.Reader) (err error) {
+	// Make the paused struct point to OD fields
+	// So gob loads values into the OD struct
+	paused := PausedOD {
+		Task:       &od.Task,
+		Result:     &od.Result,
+		BaseUri:    &od.BaseUri,
+	}
+
+	var version [8]byte
+	_, err = io.ReadFull(r, version[:])
+	if err != nil { return err }
+	if !bytes.Equal(version[:], []byte("ODPAUSE-")) {
+		return fmt.Errorf("unsupported pause file")
+	}
+
+	// Read pause settings len
+	var pauseSettingsLen uint64
+	err = binary.Read(r, binary.LittleEndian, &pauseSettingsLen)
+
+	// Read pause settings
+	pauseDec := gob.NewDecoder(io.LimitReader(r, int64(pauseSettingsLen)))
+	err = pauseDec.Decode(&paused)
+	if err != nil { return err }
+	atomic.StoreInt64(&od.InProgress, paused.InProgress)
+
+	err = readPauseStateTree(od, r)
+	if err != nil {
+		return fmt.Errorf("failed to read state tree: %s", err)
+	}
+
+	return nil
+}
+
+func readPauseStateTree(od *OD, r io.Reader) (err error) {
+	// Read pause scan state
+	err = od.Scanned.Unmarshal(r)
+	if err != nil { return err }
+
+	// Check mark
+	var mark [8]byte
+	_, err = io.ReadFull(r, mark[:])
+	if err != nil { return err }
+	if !bytes.Equal(mark[:], []byte("--------")) {
+		return fmt.Errorf("corrupt pause file")
+	}
+
+	return nil
+}

resume_test.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"bytes"
+	"github.com/terorie/od-database-crawler/fasturl"
+	"testing"
+	"time"
+)
+
+func TestResumeTasks_Empty(t *testing.T) {
+	start := time.Now().Add(-1 * time.Minute)
+	od := OD {
+		Task: Task {
+			WebsiteId: 213,
+			Url: "https://the-eye.eu/public/",
+		},
+		Result: TaskResult {
+			StartTime: start,
+			StartTimeUnix: start.Unix(),
+			EndTimeUnix: time.Now().Unix(),
+			WebsiteId: 213,
+		},
+		InProgress: 0,
+		BaseUri: fasturl.URL {
+			Scheme: fasturl.SchemeHTTPS,
+			Host: "the-eye.eu",
+			Path: "/public/",
+		},
+	}
+	od.WCtx.OD = &od
+
+	var b bytes.Buffer
+	var err error
+	err = writePauseFile(&od, &b)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	buf := b.Bytes()
+
+	var od2 OD
+
+	b2 := bytes.NewBuffer(buf)
+	err = readPauseFile(&od2, b2)
+	if err != nil {
+		t.Fatal(err)
+	}
+}

scheduler.go

@@ -22,6 +22,13 @@ func Schedule(c context.Context, remotes <-chan *OD) {
 	go Stats(c)
 
 	for remote := range remotes {
+		if !scheduleNewTask(c, remote) {
+			return
+		}
+	}
+}
+
+func scheduleNewTask(c context.Context, remote *OD) bool {
 	logrus.WithField("url", remote.BaseUri.String()).
 		Info("Starting crawler")
 
@@ -43,9 +50,7 @@ func Schedule(c context.Context, remotes <-chan *OD) {
 	if err != nil { panic(err) }
 
 	// Spawn workers
-		for i := 0; i < config.Workers; i++ {
+	remote.WCtx.SpawnWorkers(c, results, config.Workers)
-			go remote.WCtx.Worker(results)
-		}
 
 	// Enqueue initial job
 	atomic.AddInt32(&numActiveTasks, 1)
@@ -60,14 +65,12 @@ func Schedule(c context.Context, remotes <-chan *OD) {
 
 	// Sleep if max number of tasks are active
 	for atomic.LoadInt32(&numActiveTasks) > config.Tasks {
-			select {
+		if !sleep(time.Second, c) {
-			case <-c.Done():
+			break
-				return
-			case <-time.After(time.Second):
-				continue
-			}
 		}
 	}
+
+	return true
 }
 
 func ScheduleTask(remotes chan<- *OD, t *Task, u *fasturl.URL) {
@@ -117,7 +120,7 @@ func (o *OD) Watch(results chan File) {
 	// Open crawl results file
 	f, err := os.OpenFile(
 		filePath,
-		os.O_CREATE | os.O_RDWR | os.O_TRUNC,
+		os.O_CREATE | os.O_RDWR | os.O_APPEND,
 		0644,
 	)
 	if err != nil {
@@ -159,16 +162,33 @@ func (o *OD) handleCollect(results chan File, f *os.File, collectErrC chan error
 	defer close(results)
 
 	// Wait for all jobs on remote to finish
-	o.Wait.Wait()
+	for {
+		// Natural finish
+		if atomic.LoadInt64(&o.InProgress) == 0 {
+			o.onTaskFinished()
+			return
+		}
+		// Abort
+		if atomic.LoadInt32(&o.WCtx.aborted) != 0 {
+			// Wait for all workers to finish
+			o.WCtx.workers.Wait()
+			o.onTaskPaused()
+			return
+		}
+
+		time.Sleep(500 * time.Millisecond)
+	}
+}
+
+func (o *OD) onTaskFinished() {
+	defer atomic.AddInt32(&numActiveTasks, -1)
 
 	// 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(),
@@ -191,6 +211,37 @@ func (o *OD) handleCollect(results chan File, f *os.File, collectErrC chan error
 	}
 }
 
+func (o *OD) onTaskPaused() {
+	defer atomic.AddInt32(&numActiveTasks, -1)
+
+	// Close queue
+	if err := o.WCtx.Queue.Close(); err != nil {
+		panic(err)
+	}
+
+	// Set current end time
+	o.Result.EndTimeUnix = time.Now().Unix()
+
+	// Save task metadata
+	err := SaveTask(o)
+	if err != nil {
+		// Log finish
+		logrus.WithFields(logrus.Fields{
+			"err": err.Error(),
+			"id":  o.Task.WebsiteId,
+			"url": o.BaseUri.String(),
+		}).Error("Failed to save crawler state")
+		return
+	}
+
+	// Log finish
+	logrus.WithFields(logrus.Fields{
+		"id":  o.Task.WebsiteId,
+		"url": o.BaseUri.String(),
+		"duration": time.Since(o.Result.StartTime),
+	}).Info("Crawler paused")
+}
+
 func (t *Task) Collect(results chan File, f *os.File, errC chan<- error) {
 	err := t.collect(results, f)
 	if err != nil {

worker.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"github.com/beeker1121/goque"
 	"github.com/sirupsen/logrus"
 	"math"
@@ -18,10 +19,29 @@ type WorkerContext struct {
 	Queue *BufferedQueue
 	lastRateLimit time.Time
 	numRateLimits int
+	workers sync.WaitGroup
+	aborted int32
 }
 
-func (w *WorkerContext) Worker(results chan<- File) {
+func (w *WorkerContext) SpawnWorkers(c context.Context, results chan<- File, n int) {
+	w.workers.Add(n)
+	for i := 0; i < n; i++ {
+		go w.Worker(c, results)
+	}
+}
+
+func (w *WorkerContext) Worker(c context.Context, results chan<- File) {
+	defer w.workers.Done()
+
 	for {
+		select {
+		case <-c.Done():
+			// Not yet done
+			atomic.StoreInt32(&w.aborted, 1)
+			return
+		default:
+		}
+
 		job, err := w.Queue.Dequeue()
 		switch err {
 		case goque.ErrEmpty:
@@ -156,7 +176,7 @@ func (w *WorkerContext) DoJob(job *Job, f *File) (newJobs []Job, err error) {
 }
 
 func (w *WorkerContext) queueJob(job Job) {
-	w.OD.Wait.Add(1)
+	atomic.AddInt64(&w.OD.InProgress, 1)
 
 	if w.numRateLimits > 0 {
 		if time.Since(w.lastRateLimit) > 5 * time.Second {
@@ -173,7 +193,7 @@ func (w *WorkerContext) queueJob(job Job) {
 }
 
 func (w *WorkerContext) finishJob() {
-	w.OD.Wait.Done()
+	atomic.AddInt64(&w.OD.InProgress, -1)
 }
 
 func isErrSilent(err error) bool {