event: add new Subscription type and related utilities
This commit introduces a new Subscription type, which is synonymous with ethereum.Subscription. It also adds a couple of utilities that make working with Subscriptions easier. The mot complex utility is Feed, a synchronisation device that implements broadcast subscriptions. Feed is slightly faster than TypeMux and will replace uses of TypeMux across the go-ethereum codebase in the future.
This commit is contained in:
Felix Lange
226
event/feed_test.go
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226
event/feed_test.go
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// 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 event
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import (
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"fmt"
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"reflect"
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"sync"
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"testing"
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"time"
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)
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func TestFeedPanics(t *testing.T) {
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{
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var f Feed
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f.Send(int(2))
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want := feedTypeError{op: "Send", got: reflect.TypeOf(uint64(0)), want: reflect.TypeOf(int(0))}
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if err := checkPanic(want, func() { f.Send(uint64(2)) }); err != nil {
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t.Error(err)
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}
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}
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{
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var f Feed
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ch := make(chan int)
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f.Subscribe(ch)
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want := feedTypeError{op: "Send", got: reflect.TypeOf(uint64(0)), want: reflect.TypeOf(int(0))}
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if err := checkPanic(want, func() { f.Send(uint64(2)) }); err != nil {
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t.Error(err)
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}
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}
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{
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var f Feed
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f.Send(int(2))
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want := feedTypeError{op: "Subscribe", got: reflect.TypeOf(make(chan uint64)), want: reflect.TypeOf(make(chan<- int))}
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if err := checkPanic(want, func() { f.Subscribe(make(chan uint64)) }); err != nil {
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t.Error(err)
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}
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}
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{
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var f Feed
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if err := checkPanic(errBadChannel, func() { f.Subscribe(make(<-chan int)) }); err != nil {
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t.Error(err)
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}
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}
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{
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var f Feed
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if err := checkPanic(errBadChannel, func() { f.Subscribe(int(0)) }); err != nil {
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t.Error(err)
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}
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}
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}
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func checkPanic(want error, fn func()) (err error) {
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defer func() {
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panic := recover()
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if panic == nil {
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err = fmt.Errorf("didn't panic")
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} else if !reflect.DeepEqual(panic, want) {
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err = fmt.Errorf("panicked with wrong error: got %q, want %q", panic, want)
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}
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}()
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fn()
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return nil
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}
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func TestFeed(t *testing.T) {
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var feed Feed
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var done, subscribed sync.WaitGroup
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subscriber := func(i int) {
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defer done.Done()
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subchan := make(chan int)
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sub := feed.Subscribe(subchan)
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timeout := time.NewTimer(2 * time.Second)
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subscribed.Done()
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select {
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case v := <-subchan:
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if v != 1 {
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t.Errorf("%d: received value %d, want 1", i, v)
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}
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case <-timeout.C:
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t.Errorf("%d: receive timeout", i)
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}
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sub.Unsubscribe()
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select {
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case _, ok := <-sub.Err():
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if ok {
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t.Errorf("%d: error channel not closed after unsubscribe", i)
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}
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case <-timeout.C:
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t.Errorf("%d: unsubscribe timeout", i)
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}
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}
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const n = 1000
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done.Add(n)
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subscribed.Add(n)
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for i := 0; i < n; i++ {
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go subscriber(i)
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}
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subscribed.Wait()
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if nsent := feed.Send(1); nsent != n {
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t.Errorf("first send delivered %d times, want %d", nsent, n)
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}
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if nsent := feed.Send(2); nsent != 0 {
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t.Errorf("second send delivered %d times, want 0", nsent)
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}
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done.Wait()
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}
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func TestFeedSubscribeSameChannel(t *testing.T) {
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var (
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feed Feed
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done sync.WaitGroup
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ch = make(chan int)
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sub1 = feed.Subscribe(ch)
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sub2 = feed.Subscribe(ch)
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_ = feed.Subscribe(ch)
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)
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expectSends := func(value, n int) {
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if nsent := feed.Send(value); nsent != n {
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t.Errorf("send delivered %d times, want %d", nsent, n)
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}
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done.Done()
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}
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expectRecv := func(wantValue, n int) {
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for i := 0; i < n; i++ {
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if v := <-ch; v != wantValue {
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t.Errorf("received %d, want %d", v, wantValue)
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}
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}
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}
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done.Add(1)
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go expectSends(1, 3)
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expectRecv(1, 3)
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done.Wait()
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sub1.Unsubscribe()
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done.Add(1)
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go expectSends(2, 2)
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expectRecv(2, 2)
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done.Wait()
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sub2.Unsubscribe()
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done.Add(1)
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go expectSends(3, 1)
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expectRecv(3, 1)
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done.Wait()
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}
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func TestFeedUnsubscribeFromInbox(t *testing.T) {
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var (
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feed Feed
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ch1 = make(chan int)
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ch2 = make(chan int)
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sub1 = feed.Subscribe(ch1)
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sub2 = feed.Subscribe(ch1)
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sub3 = feed.Subscribe(ch2)
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)
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if len(feed.inbox) != 3 {
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t.Errorf("inbox length != 3 after subscribe")
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}
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if len(feed.sendCases) != 1 {
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t.Errorf("sendCases is non-empty after unsubscribe")
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}
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sub1.Unsubscribe()
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sub2.Unsubscribe()
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sub3.Unsubscribe()
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if len(feed.inbox) != 0 {
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t.Errorf("inbox is non-empty after unsubscribe")
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}
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if len(feed.sendCases) != 1 {
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t.Errorf("sendCases is non-empty after unsubscribe")
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}
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}
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func BenchmarkFeedSend1000(b *testing.B) {
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var (
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done sync.WaitGroup
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feed Feed
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nsubs = 1000
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)
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subscriber := func(ch <-chan int) {
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for i := 0; i < b.N; i++ {
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<-ch
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}
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done.Done()
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}
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done.Add(nsubs)
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for i := 0; i < nsubs; i++ {
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ch := make(chan int, 200)
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feed.Subscribe(ch)
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go subscriber(ch)
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}
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// The actual benchmark.
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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if feed.Send(i) != nsubs {
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panic("wrong number of sends")
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}
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}
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b.StopTimer()
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done.Wait()
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}
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