forked from cmars/conflux
/
gossip.go
236 lines (216 loc) · 6.75 KB
/
gossip.go
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/*
conflux - Distributed database synchronization library
Based on the algorithm described in
"Set Reconciliation with Nearly Optimal Communication Complexity",
Yaron Minsky, Ari Trachtenberg, and Richard Zippel, 2004.
Copyright (C) 2012 Casey Marshall <casey.marshall@gmail.com>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, version 3.
This program 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 Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package recon
import (
"errors"
"fmt"
. "github.com/cmars/conflux"
"log"
"math/rand"
"net"
"time"
)
const GOSSIP = "gossip:"
// Gossip with remote servers, acting as a client.
func (p *Peer) Gossip() {
timer := time.NewTimer(time.Duration(0))
defer timer.Stop()
for {
select {
case stop, _ := <-p.gossipStop:
if stop != nil {
stop <- new(interface{})
}
return
case <-timer.C:
var peer net.Addr
var err error
var conn net.Conn
if p.paused {
goto DELAY
}
peer, err = p.choosePartner()
if err != nil {
if err != NoPartnersError {
log.Println(GOSSIP, "choosePartner:", err)
}
goto DELAY
}
log.Println(GOSSIP, "Initiating recon with peer", peer)
conn, err = net.DialTimeout(peer.Network(), peer.String(), time.Second)
if err != nil {
log.Println(GOSSIP, "Error connecting to", peer, ":", err)
goto DELAY
}
err = p.InitiateRecon(conn)
if err != nil {
log.Println(GOSSIP, "Recon error:", err)
}
DELAY:
// jitter the delay
timer.Reset(time.Duration(p.GossipIntervalSecs()) * time.Second)
}
}
}
var NoPartnersError error = errors.New("No recon partners configured")
var IncompatiblePeerError error = errors.New("Remote peer configuration is not compatible")
func (p *Peer) choosePartner() (net.Addr, error) {
partners, err := p.PartnerAddrs()
if err != nil {
return nil, err
}
if len(partners) == 0 {
return nil, NoPartnersError
}
return partners[rand.Intn(len(partners))], nil
}
func (p *Peer) InitiateRecon(conn net.Conn) error {
defer conn.Close()
if p.ReadTimeout() > 0 {
conn.SetReadDeadline(time.Now().Add(time.Second * time.Duration(p.ReadTimeout())))
}
remoteConfig, err := p.handleConfig(conn, GOSSIP)
if err != nil {
return err
}
// Interact with peer
return p.ExecCmd(func() error {
return p.clientRecon(conn, remoteConfig)
})
}
type msgProgress struct {
elements *ZSet
err error
flush bool
messages []ReconMsg
}
type msgProgressChan chan *msgProgress
var ReconDone = errors.New("Reconciliation Done")
func (p *Peer) clientRecon(conn net.Conn, remoteConfig *Config) error {
respSet := NewZSet()
var pendingMessages []ReconMsg
for step := range p.interactWithServer(conn) {
if step.err != nil {
if step.err == ReconDone {
log.Println(GOSSIP, "Reconcilation done.")
break
} else {
WriteMsg(conn, &Error{&textMsg{Text: step.err.Error()}})
log.Println(GOSSIP, step.err)
break
}
} else {
pendingMessages = append(pendingMessages, step.messages...)
if step.flush {
for _, msg := range pendingMessages {
WriteMsg(conn, msg)
}
pendingMessages = nil
}
}
log.Println(GOSSIP, "Add step:", step)
respSet.AddAll(step.elements)
log.Println(GOSSIP, "Recover set now:", respSet.Len(), "elements")
}
items := respSet.Items()
if len(items) > 0 {
log.Println(GOSSIP, "Sending recover:", len(items), "items")
p.RecoverChan <- &Recover{
RemoteAddr: conn.RemoteAddr(),
RemoteConfig: remoteConfig,
RemoteElements: items}
}
return nil
}
func (p *Peer) interactWithServer(conn net.Conn) msgProgressChan {
out := make(msgProgressChan)
go func() {
var resp *msgProgress
for resp == nil || resp.err == nil {
msg, err := ReadMsg(conn)
if err != nil {
log.Println(GOSSIP, "interact: msg err:", err)
out <- &msgProgress{err: err}
return
}
log.Println(GOSSIP, "interact: got msg:", msg)
switch m := msg.(type) {
case *ReconRqstPoly:
resp = p.handleReconRqstPoly(m)
case *ReconRqstFull:
resp = p.handleReconRqstFull(m)
case *Elements:
log.Println(GOSSIP, "Elements:", m.ZSet.Len())
resp = &msgProgress{elements: m.ZSet}
case *Done:
resp = &msgProgress{err: ReconDone}
case *Flush:
resp = &msgProgress{elements: NewZSet(), flush: true}
default:
resp = &msgProgress{err: errors.New(fmt.Sprintf("Unexpected message: %v", m))}
}
out <- resp
}
}()
return out
}
var ReconRqstPolyNotFound = errors.New("Peer should not receive a request for a non-existant node in ReconRqstPoly")
func (p *Peer) handleReconRqstPoly(rp *ReconRqstPoly) *msgProgress {
remoteSize := rp.Size
points := p.Points()
remoteSamples := rp.Samples
node, err := p.Node(rp.Prefix)
if err == PNodeNotFound {
return &msgProgress{err: ReconRqstPolyNotFound}
}
localSamples := node.SValues()
localSize := node.Size()
remoteSet, localSet, err := p.solve(
remoteSamples, localSamples, remoteSize, localSize, points)
if err == LowMBar {
log.Println(GOSSIP, "Low MBar")
if node.IsLeaf() || node.Size() < (p.ThreshMult()*p.MBar()) {
log.Println(GOSSIP, "Sending full elements for node:", node.Key())
return &msgProgress{elements: NewZSet(), messages: []ReconMsg{&FullElements{ZSet: NewZSet(node.Elements()...)}}}
}
}
if err != nil {
log.Println(GOSSIP, "sending SyncFail because", err)
return &msgProgress{elements: NewZSet(), messages: []ReconMsg{&SyncFail{}}}
}
log.Println(GOSSIP, "solved: localSet=", localSet, "remoteSet=", remoteSet)
return &msgProgress{elements: remoteSet, messages: []ReconMsg{&Elements{ZSet: localSet}}}
}
func (p *Peer) solve(remoteSamples, localSamples []*Zp, remoteSize, localSize int, points []*Zp) (*ZSet, *ZSet, error) {
var values []*Zp
for i, x := range remoteSamples {
values = append(values, Z(x.P).Div(x, localSamples[i]))
}
log.Println(GOSSIP, "Reconcile", values, points, remoteSize-localSize)
return Reconcile(values, points, remoteSize-localSize)
}
func (p *Peer) handleReconRqstFull(rf *ReconRqstFull) *msgProgress {
node, err := p.Node(rf.Prefix)
if err == PNodeNotFound {
return &msgProgress{err: ReconRqstPolyNotFound}
}
localset := NewZSet(node.Elements()...)
localdiff := ZSetDiff(localset, rf.Elements)
remotediff := ZSetDiff(rf.Elements, localset)
log.Println(GOSSIP, "localdiff=(", localdiff.Len(), ") remotediff=(", remotediff.Len(), ")")
return &msgProgress{elements: remotediff, messages: []ReconMsg{&Elements{ZSet: localdiff}}}
}