[go-nuts] How to test client/server connection count by testing package?

In future, could you please post working examples as links to
play.golang.org. It may be the difference between someone being able
to run your program and reproduce the problem/question, or ignoring
your email.

Hi, Dave,
I use following simple test to get a idea. (This test works).

Maybe it is caused by WaitGroup. I should use simpler logic to solve it.

::::::::::::::
multi.go
::::::::::::::
package multi

import (
"time"
)

type Server struct {
Count int
}

func (s *Server) Serve() {
for {
time.Sleep(1 * time.Second)
s.Count++
time.Sleep(2 * time.Second)
s.Count--
time.Sleep(1 * time.Hour)
}
}
::::::::::::::
multi_test.go
::::::::::::::
package multi

import (
"testing"
"time"
)

func TestMulti(t *testing.T) {
srv := &Server{}
go func() {srv.Serve()}()
time.Sleep(2 * time.Second)
if srv.Count != 1 {
t.Fatal("server should be 1 after 2 second")
}
time.Sleep(2 * time.Second)
if srv.Count != 0 {
t.Fatal("server should be 0 after 2 second")
}
}

Hi dlin,

You need to reread the go memory model document, the sample you posted has a data race.

I shorted it too much. And, now my improved version have passed the Go
1.1 new feature -race test.

::::::::::::::
multi.go
::::::::::::::
package multi

import (
"time"
"sync"
)

type Server struct {

count int
mu sync.RWMutex

}

func (s *Server) GetCount() int {
s.mu.RLock()
defer s.mu.RUnlock()
return s.count
}
func (s *Server) Serve() {
for {
time.Sleep(1 * time.Second)

s.mu.Lock()
s.count++
s.mu.Unlock()

time.Sleep(2 * time.Second)

s.mu.Lock()
s.count--
s.mu.Unlock()

time.Sleep(1 * time.Hour)
}
}

::::::::::::::
multi_test.go
::::::::::::::
package multi

import (
"testing"
"time"
)

func TestMulti(t *testing.T) {
srv := &Server{}
go func() {srv.Serve()}()
time.Sleep(2 * time.Second)
n := srv.GetCount()
if n != 1 {
t.Fatal("server should be 1 after 2 second, but got", n)
}
time.Sleep(2 * time.Second)
n = srv.GetCount()
if n != 0 {
t.Fatal("server should be 0 after 2 second, but got", n)
}


*******************
Here is the running log.
*******************

14:19:21$ go build
14:19:25$ go test
PASS
ok _/home/dlin/tmp/multi 4.023s
14:19:31$ go test -race
warning: building out-of-date packages: ( I don't know why, I build Go by
myself)
runtime
runtime/cgo
runtime/race
sync/atomic
sync
errors
syscall
time
io
unicode
unicode/utf8
bytes
math
os
strconv
reflect
fmt
sort
flag
bufio
strings
text/tabwriter
runtime/pprof
testing
regexp/syntax
regexp
installing these packages with 'go test -race -i' will speed future tests.

PASS
ok _/home/dlin/tmp/multi 5.038s

You need to "go install -race". The "-race" library binaries get installed
to a directory named ${PLATFORM}_race instead of just ${PLATFORM}. Hence
why it's building them every time, since they were never installed.

Instead of protecting your counter with a mutex, you could also use the
AddInt64 and LoadInt64 functions of the "sync/atomic" package. These are
low-level synchronization primitives that are also used by the mutex
implementation, but by using them directly, you can drastically improve the
performance (and in this case also the complexity) of your program.

-christoph