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pull.go 9.12 KB
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/*
Copyright IBM Corp. All Rights Reserved.
SPDX-License-Identifier: Apache-2.0
*/
package algo
import (
"sync"
"sync/atomic"
"time"
"github.com/hyperledger/fabric/gossip/util"
)
/* PullEngine is an object that performs pull-based gossip, and maintains an internal state of items
identified by string numbers.
The protocol is as follows:
1) The Initiator sends a Hello message with a specific NONCE to a set of remote peers.
2) Each remote peer responds with a digest of its messages and returns that NONCE.
3) The initiator checks the validity of the NONCEs received, aggregates the digests,
and crafts a request containing specific item ids it wants to receive from each remote peer and then
sends each request to its corresponding peer.
4) Each peer sends back the response containing the items requested, if it still holds them and the NONCE.
Other peer Initiator
O <-------- Hello <NONCE> ------------------------- O
/|\ --------- Digest <[3,5,8, 10...], NONCE> --------> /|\
| <-------- Request <[3,8], NONCE> ----------------- |
/ \ --------- Response <[item3, item8], NONCE>-------> / \
*/
const (
DefDigestWaitTime = 1000 * time.Millisecond
DefRequestWaitTime = 1500 * time.Millisecond
DefResponseWaitTime = 2000 * time.Millisecond
)
// DigestFilter filters digests to be sent to a remote peer that
// sent a hello or a request, based on its messages's context
type DigestFilter func(context interface{}) func(digestItem string) bool
// PullAdapter is needed by the PullEngine in order to
// send messages to the remote PullEngine instances.
// The PullEngine expects to be invoked with
// OnHello, OnDigest, OnReq, OnRes when the respective message arrives
// from a remote PullEngine
type PullAdapter interface {
// SelectPeers returns a slice of peers which the engine will initiate the protocol with
SelectPeers() []string
// Hello sends a hello message to initiate the protocol
// and returns an NONCE that is expected to be returned
// in the digest message.
Hello(dest string, nonce uint64)
// SendDigest sends a digest to a remote PullEngine.
// The context parameter specifies the remote engine to send to.
SendDigest(digest []string, nonce uint64, context interface{})
// SendReq sends an array of items to a certain remote PullEngine identified
// by a string
SendReq(dest string, items []string, nonce uint64)
// SendRes sends an array of items to a remote PullEngine identified by a context.
SendRes(items []string, context interface{}, nonce uint64)
}
// PullEngine is the component that actually invokes the pull algorithm
// with the help of the PullAdapter
type PullEngine struct {
PullAdapter
stopFlag int32
state *util.Set
item2owners map[string][]string
peers2nonces map[string]uint64
nonces2peers map[uint64]string
acceptingDigests int32
acceptingResponses int32
lock sync.Mutex
outgoingNONCES *util.Set
incomingNONCES *util.Set
digFilter DigestFilter
digestWaitTime time.Duration
requestWaitTime time.Duration
responseWaitTime time.Duration
}
// PullEngineConfig is the configuration required to initialize a new pull engine
type PullEngineConfig struct {
DigestWaitTime time.Duration
RequestWaitTime time.Duration
ResponseWaitTime time.Duration
}
// NewPullEngineWithFilter creates an instance of a PullEngine with a certain sleep time
// between pull initiations, and uses the given filters when sending digests and responses
func NewPullEngineWithFilter(participant PullAdapter, sleepTime time.Duration, df DigestFilter,
config PullEngineConfig) *PullEngine {
engine := &PullEngine{
PullAdapter: participant,
stopFlag: int32(0),
state: util.NewSet(),
item2owners: make(map[string][]string),
peers2nonces: make(map[string]uint64),
nonces2peers: make(map[uint64]string),
acceptingDigests: int32(0),
acceptingResponses: int32(0),
incomingNONCES: util.NewSet(),
outgoingNONCES: util.NewSet(),
digFilter: df,
digestWaitTime: config.DigestWaitTime,
requestWaitTime: config.RequestWaitTime,
responseWaitTime: config.ResponseWaitTime,
}
go func() {
for !engine.toDie() {
time.Sleep(sleepTime)
if engine.toDie() {
return
}
engine.initiatePull()
}
}()
return engine
}
// NewPullEngine creates an instance of a PullEngine with a certain sleep time
// between pull initiations
func NewPullEngine(participant PullAdapter, sleepTime time.Duration, config PullEngineConfig) *PullEngine {
acceptAllFilter := func(_ interface{}) func(string) bool {
return func(_ string) bool {
return true
}
}
return NewPullEngineWithFilter(participant, sleepTime, acceptAllFilter, config)
}
func (engine *PullEngine) toDie() bool {
return atomic.LoadInt32(&(engine.stopFlag)) == int32(1)
}
func (engine *PullEngine) acceptResponses() {
atomic.StoreInt32(&(engine.acceptingResponses), int32(1))
}
func (engine *PullEngine) isAcceptingResponses() bool {
return atomic.LoadInt32(&(engine.acceptingResponses)) == int32(1)
}
func (engine *PullEngine) acceptDigests() {
atomic.StoreInt32(&(engine.acceptingDigests), int32(1))
}
func (engine *PullEngine) isAcceptingDigests() bool {
return atomic.LoadInt32(&(engine.acceptingDigests)) == int32(1)
}
func (engine *PullEngine) ignoreDigests() {
atomic.StoreInt32(&(engine.acceptingDigests), int32(0))
}
// Stop stops the engine
func (engine *PullEngine) Stop() {
atomic.StoreInt32(&(engine.stopFlag), int32(1))
}
func (engine *PullEngine) initiatePull() {
engine.lock.Lock()
defer engine.lock.Unlock()
engine.acceptDigests()
for _, peer := range engine.SelectPeers() {
nonce := engine.newNONCE()
engine.outgoingNONCES.Add(nonce)
engine.nonces2peers[nonce] = peer
engine.peers2nonces[peer] = nonce
engine.Hello(peer, nonce)
}
time.AfterFunc(engine.digestWaitTime, func() {
engine.processIncomingDigests()
})
}
func (engine *PullEngine) processIncomingDigests() {
engine.ignoreDigests()
engine.lock.Lock()
defer engine.lock.Unlock()
requestMapping := make(map[string][]string)
for n, sources := range engine.item2owners {
// select a random source
source := sources[util.RandomInt(len(sources))]
if _, exists := requestMapping[source]; !exists {
requestMapping[source] = make([]string, 0)
}
// append the number to that source
requestMapping[source] = append(requestMapping[source], n)
}
engine.acceptResponses()
for dest, seqsToReq := range requestMapping {
engine.SendReq(dest, seqsToReq, engine.peers2nonces[dest])
}
time.AfterFunc(engine.responseWaitTime, engine.endPull)
}
func (engine *PullEngine) endPull() {
engine.lock.Lock()
defer engine.lock.Unlock()
atomic.StoreInt32(&(engine.acceptingResponses), int32(0))
engine.outgoingNONCES.Clear()
engine.item2owners = make(map[string][]string)
engine.peers2nonces = make(map[string]uint64)
engine.nonces2peers = make(map[uint64]string)
}
// OnDigest notifies the engine that a digest has arrived
func (engine *PullEngine) OnDigest(digest []string, nonce uint64, context interface{}) {
if !engine.isAcceptingDigests() || !engine.outgoingNONCES.Exists(nonce) {
return
}
engine.lock.Lock()
defer engine.lock.Unlock()
for _, n := range digest {
if engine.state.Exists(n) {
continue
}
if _, exists := engine.item2owners[n]; !exists {
engine.item2owners[n] = make([]string, 0)
}
engine.item2owners[n] = append(engine.item2owners[n], engine.nonces2peers[nonce])
}
}
// Add adds items to the state
func (engine *PullEngine) Add(seqs ...string) {
for _, seq := range seqs {
engine.state.Add(seq)
}
}
// Remove removes items from the state
func (engine *PullEngine) Remove(seqs ...string) {
for _, seq := range seqs {
engine.state.Remove(seq)
}
}
// OnHello notifies the engine a hello has arrived
func (engine *PullEngine) OnHello(nonce uint64, context interface{}) {
engine.incomingNONCES.Add(nonce)
time.AfterFunc(engine.requestWaitTime, func() {
engine.incomingNONCES.Remove(nonce)
})
a := engine.state.ToArray()
var digest []string
filter := engine.digFilter(context)
for _, item := range a {
dig := item.(string)
if !filter(dig) {
continue
}
digest = append(digest, dig)
}
if len(digest) == 0 {
return
}
engine.SendDigest(digest, nonce, context)
}
// OnReq notifies the engine a request has arrived
func (engine *PullEngine) OnReq(items []string, nonce uint64, context interface{}) {
if !engine.incomingNONCES.Exists(nonce) {
return
}
engine.lock.Lock()
defer engine.lock.Unlock()
filter := engine.digFilter(context)
var items2Send []string
for _, item := range items {
if engine.state.Exists(item) && filter(item) {
items2Send = append(items2Send, item)
}
}
if len(items2Send) == 0 {
return
}
go engine.SendRes(items2Send, context, nonce)
}
// OnRes notifies the engine a response has arrived
func (engine *PullEngine) OnRes(items []string, nonce uint64) {
if !engine.outgoingNONCES.Exists(nonce) || !engine.isAcceptingResponses() {
return
}
engine.Add(items...)
}
func (engine *PullEngine) newNONCE() uint64 {
n := uint64(0)
for {
n = util.RandomUInt64()
if !engine.outgoingNONCES.Exists(n) {
return n
}
}
}
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