Unbroken, yay.

README.md

@@ -5,8 +5,6 @@ Bitcoin node network crawler (written in golang).
 This is a for-fun project to explore the Bitcoin protocol and network.
 
 Current status: 
-* **XXX:*** Broken. In the process of a major refactor which has a bug that
-  keeps thinking it's done prematurely.
 * JSON streaming is in place, and graceful shutdown.
 * ~~It crawls with all kinds of nice parameters but stores everything in memory
   until dumping a giant JSON blob at the end.~~
@@ -36,7 +34,8 @@ known nodes, but usually only several have timestamps within the last hour.
 (In approximate order of priority)
 
 * Apply peer-age filter to results
-* Add timeout option.
+* Output using some space-conscious format. Right now the output file grows
+  fairly quickly.
 * Namespace useful sub-packages properly (outside of `main`)
 
 

cmd.go

@@ -102,12 +102,8 @@ func main() {
 	signal.Notify(sig, os.Interrupt)
 	go func() {
 		<-sig // Wait for ^C signal
-		logger.Warningf("Interrupt signal detected, shutting down gracefully by waiting for active workers to finish.")
+		logger.Warningf("Interrupt signal detected, shutting down.")
 		crawler.Shutdown()
-
-		<-sig // Hurry up?
-		logger.Warningf("Urgent interrupt. Abandoning in-progress workers.")
-		crawler.Shutdown() // FIXME: Could this cause stuff to asplode?
 	}()
 
 	// Launch crawler

crawler.go

@@ -21,7 +21,7 @@ type Crawler struct {
 	PeerAge        time.Duration
 	ConnectTimeout time.Duration
 	shutdown       chan struct{}
-	wait           sync.WaitGroup
+	waitGroup      *sync.WaitGroup
 }
 
 type Result struct {
@@ -30,16 +30,18 @@ type Result struct {
 }
 
 func NewCrawler(client *Client, seeds []string) *Crawler {
+	var wg sync.WaitGroup
+
 	c := Crawler{
 		client:     client,
 		seenFilter: map[string]bool{},
 		shutdown:   make(chan struct{}, 1),
-		wait:       sync.WaitGroup{},
+		waitGroup:  &wg,
 	}
 	filter := func(address string) *string {
 		return c.filter(address)
 	}
-	c.queue = queue.NewQueue(filter, &c.wait)
+	c.queue = queue.NewQueue(filter, &wg)
 
 	// Prefill the queue
 	for _, address := range seeds {
@@ -140,7 +142,10 @@ func (c *Crawler) process(r *Result) *Result {
 			continue
 		}
 
-		c.queue.Add(NetAddressKey(addr))
+		c.waitGroup.Add(1)
+		if !c.queue.Add(NetAddressKey(addr)) {
+			c.waitGroup.Done()
+		}
 	}
 
 	if len(r.Peers) > 0 {
@@ -167,9 +172,7 @@ func (c *Crawler) Run(numWorkers int) <-chan Result {
 			}
 
 			// Start worker
-			c.wait.Add(1)
 			go func() {
-				logger.Debugf("[%s] Work received.", address)
 				r := c.handleAddress(address)
 
 				// Process the result
@@ -179,22 +182,17 @@ func (c *Crawler) Run(numWorkers int) <-chan Result {
 
 				// Clear worker slot
 				<-workerChan
-				c.wait.Done()
-				logger.Debugf("[%s] Work completed.", address)
+				c.waitGroup.Done()
 			}()
 		}
 
-		logger.Infof("Done after %d queued items.", c.queue.Count())
+		logger.Infof("Stopping queue after %d added items.", c.queue.Count())
+		close(result)
 	}()
 
 	go func() {
 		<-c.shutdown
-		logger.Infof("Shutting down after workers finish.")
 		isDone = true
-
-		// Urgent.
-		<-c.shutdown
-		close(result)
 	}()
 
 	return result

queue/queue.go

@@ -33,8 +33,6 @@ func (q *Queue) Add(item string) bool {
 	q.storage = append(q.storage, *r)
 	q.count++
 	q.Unlock()
-
-	q.waitGroup.Add(1)
 	q.cond.Signal()
 
 	return true
@@ -51,7 +49,6 @@ func (q *Queue) Iter() <-chan string {
 	go func() {
 		for {
 			q.Lock()
-
 			if len(q.storage) == 0 {
 				// Wait until next Add
 				q.cond.Wait()
@@ -59,14 +56,13 @@ func (q *Queue) Iter() <-chan string {
 				if len(q.storage) == 0 {
 					// Queue is finished
 					close(ch)
+					q.Unlock()
 					return
 				}
 			}
 
 			r := q.storage[0]
 			q.storage = q.storage[1:]
-
-			q.waitGroup.Done()
 			q.Unlock()
 
 			ch <- r