241 lines
6.5 KiB
Go
241 lines
6.5 KiB
Go
// Copyright 2016 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// Package flowcontrol implements a client side flow control mechanism
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package flowcontrol
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import (
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"sync"
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"time"
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"github.com/ethereum/go-ethereum/common/mclock"
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)
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const fcTimeConst = time.Millisecond
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type ServerParams struct {
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BufLimit, MinRecharge uint64
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}
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type ClientNode struct {
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params *ServerParams
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bufValue uint64
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lastTime mclock.AbsTime
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lock sync.Mutex
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cm *ClientManager
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cmNode *cmNode
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}
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func NewClientNode(cm *ClientManager, params *ServerParams) *ClientNode {
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node := &ClientNode{
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cm: cm,
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params: params,
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bufValue: params.BufLimit,
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lastTime: mclock.Now(),
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}
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node.cmNode = cm.addNode(node)
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return node
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}
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func (peer *ClientNode) Remove(cm *ClientManager) {
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cm.removeNode(peer.cmNode)
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}
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func (peer *ClientNode) recalcBV(time mclock.AbsTime) {
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dt := uint64(time - peer.lastTime)
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if time < peer.lastTime {
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dt = 0
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}
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peer.bufValue += peer.params.MinRecharge * dt / uint64(fcTimeConst)
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if peer.bufValue > peer.params.BufLimit {
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peer.bufValue = peer.params.BufLimit
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}
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peer.lastTime = time
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}
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func (peer *ClientNode) AcceptRequest() (uint64, bool) {
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peer.lock.Lock()
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defer peer.lock.Unlock()
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time := mclock.Now()
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peer.recalcBV(time)
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return peer.bufValue, peer.cm.accept(peer.cmNode, time)
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}
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func (peer *ClientNode) RequestProcessed(cost uint64) (bv, realCost uint64) {
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peer.lock.Lock()
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defer peer.lock.Unlock()
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time := mclock.Now()
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peer.recalcBV(time)
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peer.bufValue -= cost
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peer.recalcBV(time)
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rcValue, rcost := peer.cm.processed(peer.cmNode, time)
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if rcValue < peer.params.BufLimit {
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bv := peer.params.BufLimit - rcValue
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if bv > peer.bufValue {
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peer.bufValue = bv
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}
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}
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return peer.bufValue, rcost
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}
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type ServerNode struct {
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bufEstimate uint64
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lastTime mclock.AbsTime
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params *ServerParams
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sumCost uint64 // sum of req costs sent to this server
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pending map[uint64]uint64 // value = sumCost after sending the given req
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assignedRequest uint64 // when != 0, only the request with the given ID can be sent to this peer
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assignToken chan struct{} // send to this channel before assigning, read from it after deassigning
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lock sync.RWMutex
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}
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func NewServerNode(params *ServerParams) *ServerNode {
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return &ServerNode{
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bufEstimate: params.BufLimit,
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lastTime: mclock.Now(),
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params: params,
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pending: make(map[uint64]uint64),
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assignToken: make(chan struct{}, 1),
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}
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}
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func (peer *ServerNode) recalcBLE(time mclock.AbsTime) {
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dt := uint64(time - peer.lastTime)
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if time < peer.lastTime {
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dt = 0
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}
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peer.bufEstimate += peer.params.MinRecharge * dt / uint64(fcTimeConst)
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if peer.bufEstimate > peer.params.BufLimit {
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peer.bufEstimate = peer.params.BufLimit
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}
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peer.lastTime = time
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}
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// safetyMargin is added to the flow control waiting time when estimated buffer value is low
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const safetyMargin = time.Millisecond * 200
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func (peer *ServerNode) canSend(maxCost uint64) time.Duration {
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maxCost += uint64(safetyMargin) * peer.params.MinRecharge / uint64(fcTimeConst)
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if maxCost > peer.params.BufLimit {
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maxCost = peer.params.BufLimit
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}
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if peer.bufEstimate >= maxCost {
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return 0
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}
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return time.Duration((maxCost - peer.bufEstimate) * uint64(fcTimeConst) / peer.params.MinRecharge)
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}
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// CanSend returns the minimum waiting time required before sending a request
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// with the given maximum estimated cost
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func (peer *ServerNode) CanSend(maxCost uint64) time.Duration {
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peer.lock.RLock()
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defer peer.lock.RUnlock()
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return peer.canSend(maxCost)
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}
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// AssignRequest tries to assign the server node to the given request, guaranteeing
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// that once it returns true, no request will be sent to the node before this one
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func (peer *ServerNode) AssignRequest(reqID uint64) bool {
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select {
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case peer.assignToken <- struct{}{}:
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default:
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return false
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}
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peer.lock.Lock()
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peer.assignedRequest = reqID
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peer.lock.Unlock()
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return true
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}
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// MustAssignRequest waits until the node can be assigned to the given request.
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// It is always guaranteed that assignments are released in a short amount of time.
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func (peer *ServerNode) MustAssignRequest(reqID uint64) {
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peer.assignToken <- struct{}{}
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peer.lock.Lock()
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peer.assignedRequest = reqID
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peer.lock.Unlock()
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}
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// DeassignRequest releases a request assignment in case the planned request
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// is not being sent.
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func (peer *ServerNode) DeassignRequest(reqID uint64) {
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peer.lock.Lock()
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if peer.assignedRequest == reqID {
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peer.assignedRequest = 0
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<-peer.assignToken
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}
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peer.lock.Unlock()
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}
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// IsAssigned returns true if the server node has already been assigned to a request
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// (note that this function returning false does not guarantee that you can assign a request
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// immediately afterwards, its only purpose is to help peer selection)
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func (peer *ServerNode) IsAssigned() bool {
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peer.lock.RLock()
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locked := peer.assignedRequest != 0
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peer.lock.RUnlock()
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return locked
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}
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// blocks until request can be sent
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func (peer *ServerNode) SendRequest(reqID, maxCost uint64) {
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peer.lock.Lock()
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defer peer.lock.Unlock()
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if peer.assignedRequest != reqID {
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peer.lock.Unlock()
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peer.MustAssignRequest(reqID)
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peer.lock.Lock()
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}
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peer.recalcBLE(mclock.Now())
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wait := peer.canSend(maxCost)
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for wait > 0 {
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peer.lock.Unlock()
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time.Sleep(wait)
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peer.lock.Lock()
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peer.recalcBLE(mclock.Now())
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wait = peer.canSend(maxCost)
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}
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peer.assignedRequest = 0
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<-peer.assignToken
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peer.bufEstimate -= maxCost
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peer.sumCost += maxCost
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if reqID >= 0 {
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peer.pending[reqID] = peer.sumCost
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}
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}
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func (peer *ServerNode) GotReply(reqID, bv uint64) {
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peer.lock.Lock()
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defer peer.lock.Unlock()
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if bv > peer.params.BufLimit {
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bv = peer.params.BufLimit
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}
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sc, ok := peer.pending[reqID]
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if !ok {
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return
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}
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delete(peer.pending, reqID)
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peer.bufEstimate = bv - (peer.sumCost - sc)
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peer.lastTime = mclock.Now()
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}
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