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Merge pull request #777 from devlights/add-rwmutex-trylock-example
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-15
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5 files changed

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‎examples/basic/syncs/README.md

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Original file line numberDiff line numberDiff line change
@@ -20,3 +20,4 @@
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| use_pool.go | syncs_use_pool | sync.Poolのサンプルです |
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| mutex_trylock.go | syncs_mutex_trylock | Go 1.18 で追加された mutex.TryLock() についてのサンプルです。 |
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| use_rwmutex.go | syncs_use_rwmutex | sync.RWMutex のサンプルです。 |
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| rwmute_trylock.go | syncs_rwmutex_trylock | Go 1.18 で追加された RWMutex の TryLock() と TryRLock() のサンプルです。 |

‎examples/basic/syncs/examples.go

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Original file line numberDiff line numberDiff line change
@@ -29,4 +29,5 @@ func (r *register) Regist(m mapping.ExampleMapping) {
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m["syncs_use_oncevalues"] = UseOnceValues
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m["syncs_use_pool"] = UsePool
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m["syncs_mutex_trylock"] = MutexTryLock
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m["syncs_rwmutex_trylock"] = RWMutexTryLock
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}

‎examples/basic/syncs/mutex_trylock.go

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@@ -47,6 +47,7 @@ func MutexTryLock() error {
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// ここは mutex がアンロックされているのでロックが取れる
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printStatus()
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defer m.Unlock()
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5152
return nil
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‎examples/basic/syncs/rwmutex_trylock.go

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@@ -0,0 +1,160 @@
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package syncs
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import (
4+
"context"
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"log"
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"sync"
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"time"
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)
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// RWMutexTryLock は、Go 1.18 で追加された RWMutex の TryLock() と TryRLock() のサンプルです。
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//
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// 使い方としては、Mutex.TryLock() と同じ。RLockのTry版がTryRLock, LockのTry版がTryLockとなる。
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//
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// # REFERENCES
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// - https://pkg.go.dev/[email protected]#RWMutex.TryLock
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// - https://pkg.go.dev/[email protected]#RWMutex.TryRLock
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func RWMutexTryLock() error {
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//
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// 3つのゴルーチンがあり、２つは値の読み取り(RLock)、１つは値の書き込み(Lock)を行う。
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// それぞれ、ロックに入る前に TryRLock/TryLock により、ロック可能かどうかを確認する。
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//
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23+
log.SetFlags(log.Lmicroseconds)
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var (
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v int64
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m sync.RWMutex
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read = func(ctx context.Context, prefix string, interval time.Duration) {
29+
for {
30+
select {
31+
case <-ctx.Done():
32+
return
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default:
34+
}
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func() {
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log.Printf("[%s] <<<", prefix)
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for !m.TryRLock() {
39+
log.Printf("[%s] TryRLock=false", prefix)
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select {
42+
case <-ctx.Done():
43+
return
44+
case <-time.After(100 * time.Millisecond):
45+
}
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}
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log.Printf("[%s] %v", prefix, v)
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m.RUnlock()
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log.Printf("[%s] >>>", prefix)
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select {
54+
case <-ctx.Done():
55+
case <-time.After(interval):
56+
}
57+
}()
58+
}
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}
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write = func(ctx context.Context, prefix string, interval time.Duration) {
61+
for {
62+
select {
63+
case <-ctx.Done():
64+
return
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default:
66+
}
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func() {
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log.Printf("[%s] <<<", prefix)
70+
for !m.TryLock() {
71+
log.Printf("[%s] TryLock=false", prefix)
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select {
74+
case <-ctx.Done():
75+
return
76+
case <-time.After(100 * time.Millisecond):
77+
}
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}
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old := v
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v++
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log.Printf("[%s] %v --> %v", prefix, old, v)
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m.Unlock()
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log.Printf("[%s] >>>", prefix)
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select {
88+
case <-ctx.Done():
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case <-time.After(interval):
90+
}
91+
}()
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}
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}
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)
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ctx, cxl := context.WithTimeout(context.Background(), 2*time.Second)
97+
defer cxl()
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go read(ctx, "READ-1", 500*time.Millisecond)
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go read(ctx, "READ-2", 500*time.Millisecond)
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go write(ctx, "WRITE-1", 500*time.Millisecond)
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<-ctx.Done()
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log.Println("DONE")
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return nil
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/*
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$ task
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task: [build] go build .
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task: [run] ./try-golang -onetime
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ENTER EXAMPLE NAME: syncs_rwmutex_trylock
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[Name] "syncs_rwmutex_trylock"
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06:00:30.134950 [WRITE-1] <<<
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06:00:30.135052 [WRITE-1] 0 --> 1
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06:00:30.135059 [WRITE-1] >>>
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06:00:30.134976 [READ-2] <<<
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06:00:30.135079 [READ-2] 1
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06:00:30.135085 [READ-2] >>>
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06:00:30.134970 [READ-1] <<<
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06:00:30.135264 [READ-1] 1
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06:00:30.135268 [READ-1] >>>
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06:00:30.635750 [READ-1] <<<
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06:00:30.635773 [READ-1] 1
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06:00:30.635776 [READ-1] >>>
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06:00:30.635762 [READ-2] <<<
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06:00:30.635803 [READ-2] 1
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06:00:30.635812 [READ-2] >>>
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06:00:30.635787 [WRITE-1] <<<
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06:00:30.635855 [WRITE-1] 1 --> 2
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06:00:30.635867 [WRITE-1] >>>
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06:00:31.136388 [WRITE-1] <<<
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06:00:31.136406 [READ-1] <<<
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06:00:31.136411 [WRITE-1] 2 --> 3
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06:00:31.136423 [WRITE-1] >>>
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06:00:31.136422 [READ-2] <<<
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06:00:31.136430 [READ-2] 3
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06:00:31.136438 [READ-2] >>>
141+
06:00:31.136415 [READ-1] TryRLock=false
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06:00:31.236739 [READ-1] 3
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06:00:31.236767 [READ-1] >>>
144+
06:00:31.637314 [WRITE-1] <<<
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06:00:31.637340 [READ-2] <<<
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06:00:31.637367 [READ-2] TryRLock=false
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06:00:31.637335 [WRITE-1] 3 --> 4
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06:00:31.637405 [WRITE-1] >>>
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06:00:31.737604 [READ-2] 4
150+
06:00:31.737631 [READ-2] >>>
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06:00:31.737631 [READ-1] <<<
152+
06:00:31.737644 [READ-1] 4
153+
06:00:31.737653 [READ-1] >>>
154+
06:00:32.135034 DONE
155+
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[Elapsed] 2.000177751s
158+
*/
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160+
}

‎examples/basic/syncs/use_rwmutex.go

+69-15
Original file line numberDiff line numberDiff line change
@@ -51,10 +51,13 @@ func UseRWMutex() error {
5151
}
5252

5353
func() {
54+
log.Printf("[%s] <<<", prefix)
5455
m.RLock()
55-
defer m.RUnlock()
56-
57-
log.Printf("[%s] %v", prefix, v)
56+
{
57+
log.Printf("[%s] %v", prefix, v)
58+
}
59+
m.RUnlock()
60+
log.Printf("[%s] >>>", prefix)
5861

5962
select {
6063
case <-ctx.Done():
@@ -65,22 +68,22 @@ func UseRWMutex() error {
6568
}
6669
write = func(ctx context.Context, prefix string, interval time.Duration) {
6770
for {
68-
// 1秒間、RLockできる猶予を与える
6971
select {
7072
case <-ctx.Done():
7173
return
72-
case <-time.After(1 * time.Second):
74+
default:
7375
}
7476

75-
// ここから interval の間は排他ロックとなる
7677
func() {
78+
log.Printf("[%s] <<<", prefix)
7779
m.Lock()
78-
defer m.Unlock()
79-
80-
old := v
81-
v++
82-
83-
log.Printf("[%s] %v --> %v", prefix, old, v)
80+
{
81+
old := v
82+
v++
83+
log.Printf("[%s] %v --> %v", prefix, old, v)
84+
}
85+
m.Unlock()
86+
log.Printf("[%s] >>>", prefix)
8487

8588
select {
8689
case <-ctx.Done():
@@ -91,15 +94,66 @@ func UseRWMutex() error {
9194
}
9295
)
9396

94-
ctx, cxl := context.WithTimeout(context.Background(), 10*time.Second)
97+
ctx, cxl := context.WithTimeout(context.Background(), 2*time.Second)
9598
defer cxl()
9699

97100
go read(ctx, "READ-1", 500*time.Millisecond)
98-
go read(ctx, "READ-2", 250*time.Millisecond)
99-
go write(ctx, "WRITE-1", 2*time.Second)
101+
go read(ctx, "READ-2", 500*time.Millisecond)
102+
go write(ctx, "WRITE-1", 500*time.Millisecond)
100103

101104
<-ctx.Done()
102105
log.Println("DONE")
103106

104107
return nil
108+
109+
/*
110+
$ task
111+
task: [build] go build .
112+
task: [run] ./try-golang -onetime
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114+
ENTER EXAMPLE NAME: syncs_use_rwmutex
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116+
[Name] "syncs_use_rwmutex"
117+
05:57:00.082899 [WRITE-1] <<<
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05:57:00.082972 [READ-2] <<<
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05:57:00.083014 [WRITE-1] 0 --> 1
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05:57:00.083022 [WRITE-1] >>>
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05:57:00.083040 [READ-2] 1
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05:57:00.083052 [READ-2] >>>
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05:57:00.082938 [READ-1] <<<
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05:57:00.083208 [READ-1] 1
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05:57:00.083216 [READ-1] >>>
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05:57:00.583383 [READ-1] <<<
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05:57:00.583406 [READ-1] 1
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05:57:00.583409 [READ-1] >>>
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05:57:00.583422 [WRITE-1] <<<
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05:57:00.583406 [READ-2] <<<
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05:57:00.583490 [WRITE-1] 1 --> 2
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05:57:00.583512 [WRITE-1] >>>
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05:57:00.583518 [READ-2] 2
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05:57:00.583523 [READ-2] >>>
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05:57:01.083740 [READ-1] <<<
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05:57:01.083786 [READ-1] 2
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05:57:01.083801 [READ-1] >>>
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05:57:01.083774 [READ-2] <<<
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05:57:01.083829 [READ-2] 2
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05:57:01.083833 [READ-2] >>>
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05:57:01.083779 [WRITE-1] <<<
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05:57:01.083837 [WRITE-1] 2 --> 3
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05:57:01.083840 [WRITE-1] >>>
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05:57:01.584523 [WRITE-1] <<<
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05:57:01.584552 [READ-2] <<<
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05:57:01.584553 [WRITE-1] 3 --> 4
147+
05:57:01.584595 [WRITE-1] >>>
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05:57:01.584607 [READ-2] 4
149+
05:57:01.584617 [READ-2] >>>
150+
05:57:01.584542 [READ-1] <<<
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05:57:01.584623 [READ-1] 4
152+
05:57:01.584629 [READ-1] >>>
153+
05:57:02.083111 DONE
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155+
156+
[Elapsed] 2.000292011s
157+
*/
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105159
}

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