mirror of https://github.com/ethereum/go-ethereum
event: add FeedOf[T] (#26310)
This PR adds a new type event.FeedOf[T], which is like event.Feed but parameterized over the channel element type. Performance is unchanged, and it still uses reflect. But unlike Feed, the generic version doesn't need to type-check interface{} arguments. All panic cases are gone from the API.pull/26349/head
parent
3315bad256
commit
3775e198df
@ -0,0 +1,167 @@ |
|||||||
|
// Copyright 2022 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/>.
|
||||||
|
|
||||||
|
//go:build go1.18
|
||||||
|
// +build go1.18
|
||||||
|
|
||||||
|
package event |
||||||
|
|
||||||
|
import ( |
||||||
|
"reflect" |
||||||
|
"sync" |
||||||
|
) |
||||||
|
|
||||||
|
// FeedOf implements one-to-many subscriptions where the carrier of events is a channel.
|
||||||
|
// Values sent to a Feed are delivered to all subscribed channels simultaneously.
|
||||||
|
//
|
||||||
|
// The zero value is ready to use.
|
||||||
|
type FeedOf[T any] struct { |
||||||
|
once sync.Once // ensures that init only runs once
|
||||||
|
sendLock chan struct{} // sendLock has a one-element buffer and is empty when held.It protects sendCases.
|
||||||
|
removeSub chan chan<- T // interrupts Send
|
||||||
|
sendCases caseList // the active set of select cases used by Send
|
||||||
|
|
||||||
|
// The inbox holds newly subscribed channels until they are added to sendCases.
|
||||||
|
mu sync.Mutex |
||||||
|
inbox caseList |
||||||
|
} |
||||||
|
|
||||||
|
func (f *FeedOf[T]) init() { |
||||||
|
f.removeSub = make(chan chan<- T) |
||||||
|
f.sendLock = make(chan struct{}, 1) |
||||||
|
f.sendLock <- struct{}{} |
||||||
|
f.sendCases = caseList{{Chan: reflect.ValueOf(f.removeSub), Dir: reflect.SelectRecv}} |
||||||
|
} |
||||||
|
|
||||||
|
// Subscribe adds a channel to the feed. Future sends will be delivered on the channel
|
||||||
|
// until the subscription is canceled.
|
||||||
|
//
|
||||||
|
// The channel should have ample buffer space to avoid blocking other subscribers. Slow
|
||||||
|
// subscribers are not dropped.
|
||||||
|
func (f *FeedOf[T]) Subscribe(channel chan<- T) Subscription { |
||||||
|
f.once.Do(f.init) |
||||||
|
|
||||||
|
chanval := reflect.ValueOf(channel) |
||||||
|
sub := &feedOfSub[T]{feed: f, channel: channel, err: make(chan error, 1)} |
||||||
|
|
||||||
|
// Add the select case to the inbox.
|
||||||
|
// The next Send will add it to f.sendCases.
|
||||||
|
f.mu.Lock() |
||||||
|
defer f.mu.Unlock() |
||||||
|
cas := reflect.SelectCase{Dir: reflect.SelectSend, Chan: chanval} |
||||||
|
f.inbox = append(f.inbox, cas) |
||||||
|
return sub |
||||||
|
} |
||||||
|
|
||||||
|
func (f *FeedOf[T]) remove(sub *feedOfSub[T]) { |
||||||
|
// Delete from inbox first, which covers channels
|
||||||
|
// that have not been added to f.sendCases yet.
|
||||||
|
f.mu.Lock() |
||||||
|
index := f.inbox.find(sub.channel) |
||||||
|
if index != -1 { |
||||||
|
f.inbox = f.inbox.delete(index) |
||||||
|
f.mu.Unlock() |
||||||
|
return |
||||||
|
} |
||||||
|
f.mu.Unlock() |
||||||
|
|
||||||
|
select { |
||||||
|
case f.removeSub <- sub.channel: |
||||||
|
// Send will remove the channel from f.sendCases.
|
||||||
|
case <-f.sendLock: |
||||||
|
// No Send is in progress, delete the channel now that we have the send lock.
|
||||||
|
f.sendCases = f.sendCases.delete(f.sendCases.find(sub.channel)) |
||||||
|
f.sendLock <- struct{}{} |
||||||
|
} |
||||||
|
} |
||||||
|
|
||||||
|
// Send delivers to all subscribed channels simultaneously.
|
||||||
|
// It returns the number of subscribers that the value was sent to.
|
||||||
|
func (f *FeedOf[T]) Send(value T) (nsent int) { |
||||||
|
rvalue := reflect.ValueOf(value) |
||||||
|
|
||||||
|
f.once.Do(f.init) |
||||||
|
<-f.sendLock |
||||||
|
|
||||||
|
// Add new cases from the inbox after taking the send lock.
|
||||||
|
f.mu.Lock() |
||||||
|
f.sendCases = append(f.sendCases, f.inbox...) |
||||||
|
f.inbox = nil |
||||||
|
f.mu.Unlock() |
||||||
|
|
||||||
|
// Set the sent value on all channels.
|
||||||
|
for i := firstSubSendCase; i < len(f.sendCases); i++ { |
||||||
|
f.sendCases[i].Send = rvalue |
||||||
|
} |
||||||
|
|
||||||
|
// Send until all channels except removeSub have been chosen. 'cases' tracks a prefix
|
||||||
|
// of sendCases. When a send succeeds, the corresponding case moves to the end of
|
||||||
|
// 'cases' and it shrinks by one element.
|
||||||
|
cases := f.sendCases |
||||||
|
for { |
||||||
|
// Fast path: try sending without blocking before adding to the select set.
|
||||||
|
// This should usually succeed if subscribers are fast enough and have free
|
||||||
|
// buffer space.
|
||||||
|
for i := firstSubSendCase; i < len(cases); i++ { |
||||||
|
if cases[i].Chan.TrySend(rvalue) { |
||||||
|
nsent++ |
||||||
|
cases = cases.deactivate(i) |
||||||
|
i-- |
||||||
|
} |
||||||
|
} |
||||||
|
if len(cases) == firstSubSendCase { |
||||||
|
break |
||||||
|
} |
||||||
|
// Select on all the receivers, waiting for them to unblock.
|
||||||
|
chosen, recv, _ := reflect.Select(cases) |
||||||
|
if chosen == 0 /* <-f.removeSub */ { |
||||||
|
index := f.sendCases.find(recv.Interface()) |
||||||
|
f.sendCases = f.sendCases.delete(index) |
||||||
|
if index >= 0 && index < len(cases) { |
||||||
|
// Shrink 'cases' too because the removed case was still active.
|
||||||
|
cases = f.sendCases[:len(cases)-1] |
||||||
|
} |
||||||
|
} else { |
||||||
|
cases = cases.deactivate(chosen) |
||||||
|
nsent++ |
||||||
|
} |
||||||
|
} |
||||||
|
|
||||||
|
// Forget about the sent value and hand off the send lock.
|
||||||
|
for i := firstSubSendCase; i < len(f.sendCases); i++ { |
||||||
|
f.sendCases[i].Send = reflect.Value{} |
||||||
|
} |
||||||
|
f.sendLock <- struct{}{} |
||||||
|
return nsent |
||||||
|
} |
||||||
|
|
||||||
|
type feedOfSub[T any] struct { |
||||||
|
feed *FeedOf[T] |
||||||
|
channel chan<- T |
||||||
|
errOnce sync.Once |
||||||
|
err chan error |
||||||
|
} |
||||||
|
|
||||||
|
func (sub *feedOfSub[T]) Unsubscribe() { |
||||||
|
sub.errOnce.Do(func() { |
||||||
|
sub.feed.remove(sub) |
||||||
|
close(sub.err) |
||||||
|
}) |
||||||
|
} |
||||||
|
|
||||||
|
func (sub *feedOfSub[T]) Err() <-chan error { |
||||||
|
return sub.err |
||||||
|
} |
@ -0,0 +1,282 @@ |
|||||||
|
// Copyright 2016 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/>.
|
||||||
|
|
||||||
|
//go:build go1.18
|
||||||
|
// +build go1.18
|
||||||
|
|
||||||
|
package event |
||||||
|
|
||||||
|
import ( |
||||||
|
"sync" |
||||||
|
"testing" |
||||||
|
"time" |
||||||
|
) |
||||||
|
|
||||||
|
func TestFeedOf(t *testing.T) { |
||||||
|
var feed FeedOf[int] |
||||||
|
var done, subscribed sync.WaitGroup |
||||||
|
subscriber := func(i int) { |
||||||
|
defer done.Done() |
||||||
|
|
||||||
|
subchan := make(chan int) |
||||||
|
sub := feed.Subscribe(subchan) |
||||||
|
timeout := time.NewTimer(2 * time.Second) |
||||||
|
defer timeout.Stop() |
||||||
|
subscribed.Done() |
||||||
|
|
||||||
|
select { |
||||||
|
case v := <-subchan: |
||||||
|
if v != 1 { |
||||||
|
t.Errorf("%d: received value %d, want 1", i, v) |
||||||
|
} |
||||||
|
case <-timeout.C: |
||||||
|
t.Errorf("%d: receive timeout", i) |
||||||
|
} |
||||||
|
|
||||||
|
sub.Unsubscribe() |
||||||
|
select { |
||||||
|
case _, ok := <-sub.Err(): |
||||||
|
if ok { |
||||||
|
t.Errorf("%d: error channel not closed after unsubscribe", i) |
||||||
|
} |
||||||
|
case <-timeout.C: |
||||||
|
t.Errorf("%d: unsubscribe timeout", i) |
||||||
|
} |
||||||
|
} |
||||||
|
|
||||||
|
const n = 1000 |
||||||
|
done.Add(n) |
||||||
|
subscribed.Add(n) |
||||||
|
for i := 0; i < n; i++ { |
||||||
|
go subscriber(i) |
||||||
|
} |
||||||
|
subscribed.Wait() |
||||||
|
if nsent := feed.Send(1); nsent != n { |
||||||
|
t.Errorf("first send delivered %d times, want %d", nsent, n) |
||||||
|
} |
||||||
|
if nsent := feed.Send(2); nsent != 0 { |
||||||
|
t.Errorf("second send delivered %d times, want 0", nsent) |
||||||
|
} |
||||||
|
done.Wait() |
||||||
|
} |
||||||
|
|
||||||
|
func TestFeedOfSubscribeSameChannel(t *testing.T) { |
||||||
|
var ( |
||||||
|
feed FeedOf[int] |
||||||
|
done sync.WaitGroup |
||||||
|
ch = make(chan int) |
||||||
|
sub1 = feed.Subscribe(ch) |
||||||
|
sub2 = feed.Subscribe(ch) |
||||||
|
_ = feed.Subscribe(ch) |
||||||
|
) |
||||||
|
expectSends := func(value, n int) { |
||||||
|
if nsent := feed.Send(value); nsent != n { |
||||||
|
t.Errorf("send delivered %d times, want %d", nsent, n) |
||||||
|
} |
||||||
|
done.Done() |
||||||
|
} |
||||||
|
expectRecv := func(wantValue, n int) { |
||||||
|
for i := 0; i < n; i++ { |
||||||
|
if v := <-ch; v != wantValue { |
||||||
|
t.Errorf("received %d, want %d", v, wantValue) |
||||||
|
} |
||||||
|
} |
||||||
|
} |
||||||
|
|
||||||
|
done.Add(1) |
||||||
|
go expectSends(1, 3) |
||||||
|
expectRecv(1, 3) |
||||||
|
done.Wait() |
||||||
|
|
||||||
|
sub1.Unsubscribe() |
||||||
|
|
||||||
|
done.Add(1) |
||||||
|
go expectSends(2, 2) |
||||||
|
expectRecv(2, 2) |
||||||
|
done.Wait() |
||||||
|
|
||||||
|
sub2.Unsubscribe() |
||||||
|
|
||||||
|
done.Add(1) |
||||||
|
go expectSends(3, 1) |
||||||
|
expectRecv(3, 1) |
||||||
|
done.Wait() |
||||||
|
} |
||||||
|
|
||||||
|
func TestFeedOfSubscribeBlockedPost(t *testing.T) { |
||||||
|
var ( |
||||||
|
feed FeedOf[int] |
||||||
|
nsends = 2000 |
||||||
|
ch1 = make(chan int) |
||||||
|
ch2 = make(chan int) |
||||||
|
wg sync.WaitGroup |
||||||
|
) |
||||||
|
defer wg.Wait() |
||||||
|
|
||||||
|
feed.Subscribe(ch1) |
||||||
|
wg.Add(nsends) |
||||||
|
for i := 0; i < nsends; i++ { |
||||||
|
go func() { |
||||||
|
feed.Send(99) |
||||||
|
wg.Done() |
||||||
|
}() |
||||||
|
} |
||||||
|
|
||||||
|
sub2 := feed.Subscribe(ch2) |
||||||
|
defer sub2.Unsubscribe() |
||||||
|
|
||||||
|
// We're done when ch1 has received N times.
|
||||||
|
// The number of receives on ch2 depends on scheduling.
|
||||||
|
for i := 0; i < nsends; { |
||||||
|
select { |
||||||
|
case <-ch1: |
||||||
|
i++ |
||||||
|
case <-ch2: |
||||||
|
} |
||||||
|
} |
||||||
|
} |
||||||
|
|
||||||
|
func TestFeedOfUnsubscribeBlockedPost(t *testing.T) { |
||||||
|
var ( |
||||||
|
feed FeedOf[int] |
||||||
|
nsends = 200 |
||||||
|
chans = make([]chan int, 2000) |
||||||
|
subs = make([]Subscription, len(chans)) |
||||||
|
bchan = make(chan int) |
||||||
|
bsub = feed.Subscribe(bchan) |
||||||
|
wg sync.WaitGroup |
||||||
|
) |
||||||
|
for i := range chans { |
||||||
|
chans[i] = make(chan int, nsends) |
||||||
|
} |
||||||
|
|
||||||
|
// Queue up some Sends. None of these can make progress while bchan isn't read.
|
||||||
|
wg.Add(nsends) |
||||||
|
for i := 0; i < nsends; i++ { |
||||||
|
go func() { |
||||||
|
feed.Send(99) |
||||||
|
wg.Done() |
||||||
|
}() |
||||||
|
} |
||||||
|
// Subscribe the other channels.
|
||||||
|
for i, ch := range chans { |
||||||
|
subs[i] = feed.Subscribe(ch) |
||||||
|
} |
||||||
|
// Unsubscribe them again.
|
||||||
|
for _, sub := range subs { |
||||||
|
sub.Unsubscribe() |
||||||
|
} |
||||||
|
// Unblock the Sends.
|
||||||
|
bsub.Unsubscribe() |
||||||
|
wg.Wait() |
||||||
|
} |
||||||
|
|
||||||
|
// Checks that unsubscribing a channel during Send works even if that
|
||||||
|
// channel has already been sent on.
|
||||||
|
func TestFeedOfUnsubscribeSentChan(t *testing.T) { |
||||||
|
var ( |
||||||
|
feed FeedOf[int] |
||||||
|
ch1 = make(chan int) |
||||||
|
ch2 = make(chan int) |
||||||
|
sub1 = feed.Subscribe(ch1) |
||||||
|
sub2 = feed.Subscribe(ch2) |
||||||
|
wg sync.WaitGroup |
||||||
|
) |
||||||
|
defer sub2.Unsubscribe() |
||||||
|
|
||||||
|
wg.Add(1) |
||||||
|
go func() { |
||||||
|
feed.Send(0) |
||||||
|
wg.Done() |
||||||
|
}() |
||||||
|
|
||||||
|
// Wait for the value on ch1.
|
||||||
|
<-ch1 |
||||||
|
// Unsubscribe ch1, removing it from the send cases.
|
||||||
|
sub1.Unsubscribe() |
||||||
|
|
||||||
|
// Receive ch2, finishing Send.
|
||||||
|
<-ch2 |
||||||
|
wg.Wait() |
||||||
|
|
||||||
|
// Send again. This should send to ch2 only, so the wait group will unblock
|
||||||
|
// as soon as a value is received on ch2.
|
||||||
|
wg.Add(1) |
||||||
|
go func() { |
||||||
|
feed.Send(0) |
||||||
|
wg.Done() |
||||||
|
}() |
||||||
|
<-ch2 |
||||||
|
wg.Wait() |
||||||
|
} |
||||||
|
|
||||||
|
func TestFeedOfUnsubscribeFromInbox(t *testing.T) { |
||||||
|
var ( |
||||||
|
feed FeedOf[int] |
||||||
|
ch1 = make(chan int) |
||||||
|
ch2 = make(chan int) |
||||||
|
sub1 = feed.Subscribe(ch1) |
||||||
|
sub2 = feed.Subscribe(ch1) |
||||||
|
sub3 = feed.Subscribe(ch2) |
||||||
|
) |
||||||
|
if len(feed.inbox) != 3 { |
||||||
|
t.Errorf("inbox length != 3 after subscribe") |
||||||
|
} |
||||||
|
if len(feed.sendCases) != 1 { |
||||||
|
t.Errorf("sendCases is non-empty after unsubscribe") |
||||||
|
} |
||||||
|
|
||||||
|
sub1.Unsubscribe() |
||||||
|
sub2.Unsubscribe() |
||||||
|
sub3.Unsubscribe() |
||||||
|
if len(feed.inbox) != 0 { |
||||||
|
t.Errorf("inbox is non-empty after unsubscribe") |
||||||
|
} |
||||||
|
if len(feed.sendCases) != 1 { |
||||||
|
t.Errorf("sendCases is non-empty after unsubscribe") |
||||||
|
} |
||||||
|
} |
||||||
|
|
||||||
|
func BenchmarkFeedOfSend1000(b *testing.B) { |
||||||
|
var ( |
||||||
|
done sync.WaitGroup |
||||||
|
feed FeedOf[int] |
||||||
|
nsubs = 1000 |
||||||
|
) |
||||||
|
subscriber := func(ch <-chan int) { |
||||||
|
for i := 0; i < b.N; i++ { |
||||||
|
<-ch |
||||||
|
} |
||||||
|
done.Done() |
||||||
|
} |
||||||
|
done.Add(nsubs) |
||||||
|
for i := 0; i < nsubs; i++ { |
||||||
|
ch := make(chan int, 200) |
||||||
|
feed.Subscribe(ch) |
||||||
|
go subscriber(ch) |
||||||
|
} |
||||||
|
|
||||||
|
// The actual benchmark.
|
||||||
|
b.ResetTimer() |
||||||
|
for i := 0; i < b.N; i++ { |
||||||
|
if feed.Send(i) != nsubs { |
||||||
|
panic("wrong number of sends") |
||||||
|
} |
||||||
|
} |
||||||
|
|
||||||
|
b.StopTimer() |
||||||
|
done.Wait() |
||||||
|
} |
Loading…
Reference in new issue