les: light client protocol and API

les/flowcontrol/control.go

@@ -0,0 +1,172 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Package flowcontrol implements a client side flow control mechanism
+package flowcontrol
+
+import (
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common/mclock"
+)
+
+const fcTimeConst = 1000000
+
+type ServerParams struct {
+	BufLimit, MinRecharge uint64
+}
+
+type ClientNode struct {
+	params   *ServerParams
+	bufValue uint64
+	lastTime int64
+	lock     sync.Mutex
+	cm       *ClientManager
+	cmNode   *cmNode
+}
+
+func NewClientNode(cm *ClientManager, params *ServerParams) *ClientNode {
+	node := &ClientNode{
+		cm:       cm,
+		params:   params,
+		bufValue: params.BufLimit,
+		lastTime: getTime(),
+	}
+	node.cmNode = cm.addNode(node)
+	return node
+}
+
+func (peer *ClientNode) Remove(cm *ClientManager) {
+	cm.removeNode(peer.cmNode)
+}
+
+func (peer *ClientNode) recalcBV(time int64) {
+	dt := uint64(time - peer.lastTime)
+	if time < peer.lastTime {
+		dt = 0
+	}
+	peer.bufValue += peer.params.MinRecharge * dt / fcTimeConst
+	if peer.bufValue > peer.params.BufLimit {
+		peer.bufValue = peer.params.BufLimit
+	}
+	peer.lastTime = time
+}
+
+func (peer *ClientNode) AcceptRequest() (uint64, bool) {
+	peer.lock.Lock()
+	defer peer.lock.Unlock()
+
+	time := getTime()
+	peer.recalcBV(time)
+	return peer.bufValue, peer.cm.accept(peer.cmNode, time)
+}
+
+func (peer *ClientNode) RequestProcessed(cost uint64) (bv, realCost uint64) {
+	peer.lock.Lock()
+	defer peer.lock.Unlock()
+
+	time := getTime()
+	peer.recalcBV(time)
+	peer.bufValue -= cost
+	peer.recalcBV(time)
+	rcValue, rcost := peer.cm.processed(peer.cmNode, time)
+	if rcValue < peer.params.BufLimit {
+		bv := peer.params.BufLimit - rcValue
+		if bv > peer.bufValue {
+			peer.bufValue = bv
+		}
+	}
+	return peer.bufValue, rcost
+}
+
+type ServerNode struct {
+	bufEstimate uint64
+	lastTime    int64
+	params      *ServerParams
+	sumCost     uint64            // sum of req costs sent to this server
+	pending     map[uint64]uint64 // value = sumCost after sending the given req
+	lock        sync.Mutex
+}
+
+func NewServerNode(params *ServerParams) *ServerNode {
+	return &ServerNode{
+		bufEstimate: params.BufLimit,
+		lastTime:    getTime(),
+		params:      params,
+		pending:     make(map[uint64]uint64),
+	}
+}
+
+func getTime() int64 {
+	return int64(mclock.Now())
+}
+
+func (peer *ServerNode) recalcBLE(time int64) {
+	dt := uint64(time - peer.lastTime)
+	if time < peer.lastTime {
+		dt = 0
+	}
+	peer.bufEstimate += peer.params.MinRecharge * dt / fcTimeConst
+	if peer.bufEstimate > peer.params.BufLimit {
+		peer.bufEstimate = peer.params.BufLimit
+	}
+	peer.lastTime = time
+}
+
+func (peer *ServerNode) canSend(maxCost uint64) uint64 {
+	if peer.bufEstimate >= maxCost {
+		return 0
+	}
+	return (maxCost - peer.bufEstimate) * fcTimeConst / peer.params.MinRecharge
+}
+
+func (peer *ServerNode) CanSend(maxCost uint64) uint64 {
+	peer.lock.Lock()
+	defer peer.lock.Unlock()
+
+	return peer.canSend(maxCost)
+}
+
+// blocks until request can be sent
+func (peer *ServerNode) SendRequest(reqID, maxCost uint64) {
+	peer.lock.Lock()
+	defer peer.lock.Unlock()
+
+	peer.recalcBLE(getTime())
+	for peer.bufEstimate < maxCost {
+		time.Sleep(time.Duration(peer.canSend(maxCost)))
+		peer.recalcBLE(getTime())
+	}
+	peer.bufEstimate -= maxCost
+	peer.sumCost += maxCost
+	if reqID >= 0 {
+		peer.pending[reqID] = peer.sumCost
+	}
+}
+
+func (peer *ServerNode) GotReply(reqID, bv uint64) {
+	peer.lock.Lock()
+	defer peer.lock.Unlock()
+
+	sc, ok := peer.pending[reqID]
+	if !ok {
+		return
+	}
+	delete(peer.pending, reqID)
+	peer.bufEstimate = bv - (peer.sumCost - sc)
+	peer.lastTime = getTime()
+}