296 lines
7.1 KiB
Go
296 lines
7.1 KiB
Go
// Copyright 2019 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 enode
|
|
|
|
import (
|
|
"sync"
|
|
"time"
|
|
)
|
|
|
|
// Iterator represents a sequence of nodes. The Next method moves to the next node in the
|
|
// sequence. It returns false when the sequence has ended or the iterator is closed. Close
|
|
// may be called concurrently with Next and Node, and interrupts Next if it is blocked.
|
|
type Iterator interface {
|
|
Next() bool // moves to next node
|
|
Node() *Node // returns current node
|
|
Close() // ends the iterator
|
|
}
|
|
|
|
// ReadNodes reads at most n nodes from the given iterator. The return value contains no
|
|
// duplicates and no nil values. To prevent looping indefinitely for small repeating node
|
|
// sequences, this function calls Next at most n times.
|
|
func ReadNodes(it Iterator, n int) []*Node {
|
|
seen := make(map[ID]*Node, n)
|
|
for i := 0; i < n && it.Next(); i++ {
|
|
// Remove duplicates, keeping the node with higher seq.
|
|
node := it.Node()
|
|
prevNode, ok := seen[node.ID()]
|
|
if ok && prevNode.Seq() > node.Seq() {
|
|
continue
|
|
}
|
|
seen[node.ID()] = node
|
|
}
|
|
result := make([]*Node, 0, len(seen))
|
|
for _, node := range seen {
|
|
result = append(result, node)
|
|
}
|
|
return result
|
|
}
|
|
|
|
// IterNodes makes an iterator which runs through the given nodes once.
|
|
func IterNodes(nodes []*Node) Iterator {
|
|
return &sliceIter{nodes: nodes, index: -1}
|
|
}
|
|
|
|
// CycleNodes makes an iterator which cycles through the given nodes indefinitely.
|
|
func CycleNodes(nodes []*Node) Iterator {
|
|
return &sliceIter{nodes: nodes, index: -1, cycle: true}
|
|
}
|
|
|
|
type sliceIter struct {
|
|
mu sync.Mutex
|
|
nodes []*Node
|
|
index int
|
|
cycle bool
|
|
}
|
|
|
|
func (it *sliceIter) Next() bool {
|
|
it.mu.Lock()
|
|
defer it.mu.Unlock()
|
|
|
|
if len(it.nodes) == 0 {
|
|
return false
|
|
}
|
|
it.index++
|
|
if it.index == len(it.nodes) {
|
|
if it.cycle {
|
|
it.index = 0
|
|
} else {
|
|
it.nodes = nil
|
|
return false
|
|
}
|
|
}
|
|
return true
|
|
}
|
|
|
|
func (it *sliceIter) Node() *Node {
|
|
it.mu.Lock()
|
|
defer it.mu.Unlock()
|
|
if len(it.nodes) == 0 {
|
|
return nil
|
|
}
|
|
return it.nodes[it.index]
|
|
}
|
|
|
|
func (it *sliceIter) Close() {
|
|
it.mu.Lock()
|
|
defer it.mu.Unlock()
|
|
|
|
it.nodes = nil
|
|
}
|
|
|
|
// Filter wraps an iterator such that Next only returns nodes for which
|
|
// the 'check' function returns true.
|
|
func Filter(it Iterator, check func(*Node) bool) Iterator {
|
|
return &filterIter{it, check}
|
|
}
|
|
|
|
type filterIter struct {
|
|
Iterator
|
|
check func(*Node) bool
|
|
}
|
|
|
|
func (f *filterIter) Next() bool {
|
|
for f.Iterator.Next() {
|
|
if f.check(f.Node()) {
|
|
return true
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
// FairMix aggregates multiple node iterators. The mixer itself is an iterator which ends
|
|
// only when Close is called. Source iterators added via AddSource are removed from the
|
|
// mix when they end.
|
|
//
|
|
// The distribution of nodes returned by Next is approximately fair, i.e. FairMix
|
|
// attempts to draw from all sources equally often. However, if a certain source is slow
|
|
// and doesn't return a node within the configured timeout, a node from any other source
|
|
// will be returned.
|
|
//
|
|
// It's safe to call AddSource and Close concurrently with Next.
|
|
type FairMix struct {
|
|
wg sync.WaitGroup
|
|
fromAny chan *Node
|
|
timeout time.Duration
|
|
cur *Node
|
|
|
|
mu sync.Mutex
|
|
closed chan struct{}
|
|
sources []*mixSource
|
|
last int
|
|
}
|
|
|
|
type mixSource struct {
|
|
it Iterator
|
|
next chan *Node
|
|
timeout time.Duration
|
|
}
|
|
|
|
// NewFairMix creates a mixer.
|
|
//
|
|
// The timeout specifies how long the mixer will wait for the next fairly-chosen source
|
|
// before giving up and taking a node from any other source. A good way to set the timeout
|
|
// is deciding how long you'd want to wait for a node on average. Passing a negative
|
|
// timeout makes the mixer completely fair.
|
|
func NewFairMix(timeout time.Duration) *FairMix {
|
|
m := &FairMix{
|
|
fromAny: make(chan *Node),
|
|
closed: make(chan struct{}),
|
|
timeout: timeout,
|
|
}
|
|
return m
|
|
}
|
|
|
|
// AddSource adds a source of nodes.
|
|
func (m *FairMix) AddSource(it Iterator) {
|
|
m.mu.Lock()
|
|
defer m.mu.Unlock()
|
|
|
|
if m.closed == nil {
|
|
return
|
|
}
|
|
m.wg.Add(1)
|
|
source := &mixSource{it, make(chan *Node), m.timeout}
|
|
m.sources = append(m.sources, source)
|
|
go m.runSource(m.closed, source)
|
|
}
|
|
|
|
// Close shuts down the mixer and all current sources.
|
|
// Calling this is required to release resources associated with the mixer.
|
|
func (m *FairMix) Close() {
|
|
m.mu.Lock()
|
|
defer m.mu.Unlock()
|
|
|
|
if m.closed == nil {
|
|
return
|
|
}
|
|
for _, s := range m.sources {
|
|
s.it.Close()
|
|
}
|
|
close(m.closed)
|
|
m.wg.Wait()
|
|
close(m.fromAny)
|
|
m.sources = nil
|
|
m.closed = nil
|
|
}
|
|
|
|
// Next returns a node from a random source.
|
|
func (m *FairMix) Next() bool {
|
|
m.cur = nil
|
|
|
|
for {
|
|
source := m.pickSource()
|
|
if source == nil {
|
|
return m.nextFromAny()
|
|
}
|
|
|
|
var timeout <-chan time.Time
|
|
if source.timeout >= 0 {
|
|
timer := time.NewTimer(source.timeout)
|
|
timeout = timer.C
|
|
defer timer.Stop()
|
|
}
|
|
|
|
select {
|
|
case n, ok := <-source.next:
|
|
if ok {
|
|
// Here, the timeout is reset to the configured value
|
|
// because the source delivered a node.
|
|
source.timeout = m.timeout
|
|
m.cur = n
|
|
return true
|
|
}
|
|
// This source has ended.
|
|
m.deleteSource(source)
|
|
case <-timeout:
|
|
// The selected source did not deliver a node within the timeout, so the
|
|
// timeout duration is halved for next time. This is supposed to improve
|
|
// latency with stuck sources.
|
|
source.timeout /= 2
|
|
return m.nextFromAny()
|
|
}
|
|
}
|
|
}
|
|
|
|
// Node returns the current node.
|
|
func (m *FairMix) Node() *Node {
|
|
return m.cur
|
|
}
|
|
|
|
// nextFromAny is used when there are no sources or when the 'fair' choice
|
|
// doesn't turn up a node quickly enough.
|
|
func (m *FairMix) nextFromAny() bool {
|
|
n, ok := <-m.fromAny
|
|
if ok {
|
|
m.cur = n
|
|
}
|
|
return ok
|
|
}
|
|
|
|
// pickSource chooses the next source to read from, cycling through them in order.
|
|
func (m *FairMix) pickSource() *mixSource {
|
|
m.mu.Lock()
|
|
defer m.mu.Unlock()
|
|
|
|
if len(m.sources) == 0 {
|
|
return nil
|
|
}
|
|
m.last = (m.last + 1) % len(m.sources)
|
|
return m.sources[m.last]
|
|
}
|
|
|
|
// deleteSource deletes a source.
|
|
func (m *FairMix) deleteSource(s *mixSource) {
|
|
m.mu.Lock()
|
|
defer m.mu.Unlock()
|
|
|
|
for i := range m.sources {
|
|
if m.sources[i] == s {
|
|
copy(m.sources[i:], m.sources[i+1:])
|
|
m.sources[len(m.sources)-1] = nil
|
|
m.sources = m.sources[:len(m.sources)-1]
|
|
break
|
|
}
|
|
}
|
|
}
|
|
|
|
// runSource reads a single source in a loop.
|
|
func (m *FairMix) runSource(closed chan struct{}, s *mixSource) {
|
|
defer m.wg.Done()
|
|
defer close(s.next)
|
|
for s.it.Next() {
|
|
n := s.it.Node()
|
|
select {
|
|
case s.next <- n:
|
|
case m.fromAny <- n:
|
|
case <-closed:
|
|
return
|
|
}
|
|
}
|
|
}
|