Complete rewrite of the puller (fixes #638, fixes #715, fixes #701)

internal/model/nodeactivity.go

@@ -0,0 +1,51 @@
+// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
+// All rights reserved. Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package model
+
+import (
+	"sync"
+
+	"github.com/syncthing/syncthing/internal/protocol"
+)
+
+// nodeActivity tracks the number of outstanding requests per node and can
+// answer which node is least busy. It is safe for use from multiple
+// goroutines.
+type nodeActivity struct {
+	act map[protocol.NodeID]int
+	mut sync.Mutex
+}
+
+func newNodeActivity() *nodeActivity {
+	return &nodeActivity{
+		act: make(map[protocol.NodeID]int),
+	}
+}
+
+func (m nodeActivity) leastBusy(availability []protocol.NodeID) protocol.NodeID {
+	m.mut.Lock()
+	var low int = 2<<30 - 1
+	var selected protocol.NodeID
+	for _, node := range availability {
+		if usage := m.act[node]; usage < low {
+			low = usage
+			selected = node
+		}
+	}
+	m.mut.Unlock()
+	return selected
+}
+
+func (m nodeActivity) using(node protocol.NodeID) {
+	m.mut.Lock()
+	defer m.mut.Unlock()
+	m.act[node]++
+}
+
+func (m nodeActivity) done(node protocol.NodeID) {
+	m.mut.Lock()
+	defer m.mut.Unlock()
+	m.act[node]--
+}