go 작동 분석하기 (on CentOS 7)
in Back-end
strace를 이용하여 go 프로그램의 작동원리 분석하기
go 작동 분석하기 (on CentOS 7)
일단 1초마다 hello world를 출력하는 프로그램을 이용하여 어떤식으로 동작하는지 분석해보자.
Environment
MacOS (2.2 GHz Intel Core i7) 위에 docker(Version 2.0.0.0-mac81 (29211)를 이용하여
CentOS 7(2 core / 5G RAM) 사용
사용하는 패키지는 Go에서 기본으로 지원하는 패키지들이다.
fmt
package main
import (
"fmt"
"runtime"
"time"
)
func main() {
runtime.GOMAXPROCS(1)
t := time.NewTicker(time.Second * 1)
for {
select {
case <-t.C:
fmt.Println("hello world")
}
}
return
}
위와 같이 코드를 작성하고 실행시킨 후 다른 터미널을 실행시켜서 process를 확인해보자
[root@go_practice code] go run analyze.go
hello world
...
run command를 이용해서 실행시킬 경우 /tmp/go-build{hash}/command-line-arguments/_obj/exe/{filename}으로 실행이 되며 하나의 프로세스만 뜬 것 처럼 보인다.
[root@go_practice code] ps -ef | grep analyze
root 675 234 0 06:10 pts/3 00:00:00 go run analyze.go
root 695 675 0 06:10 pts/3 00:00:00 /tmp/go-build915599032/command-line-arguments/_obj/exe/analyze
ps의 L옵션을 추가하여 Thread까지 보면 다음과 같이 여러개의 LWP(Light Weight Process)가 돌아가고 있는 것을 볼 수 있다.
검색해보니 GOMAXPROCS()는 유저 레벨의 프로세스만 제한을 거는 것 같다.
Kernel scheduler가 생성하는 프로세스들에는 제한 되지 않는 듯 하다.
참고: https://stackoverflow.com/questions/46974078/runtime-gomaxprocs-not-working-as-expected
[root@go_practice code] ps -efL | grep analyze
root 675 234 675 0 6 06:10 pts/3 00:00:00 go run analyze.go
root 675 234 676 0 6 06:10 pts/3 00:00:00 go run analyze.go
root 675 234 677 0 6 06:10 pts/3 00:00:00 go run analyze.go
root 675 234 678 0 6 06:10 pts/3 00:00:00 go run analyze.go
root 675 234 679 0 6 06:10 pts/3 00:00:00 go run analyze.go
root 675 234 686 0 6 06:10 pts/3 00:00:00 go run analyze.go
root 695 675 695 0 4 06:10 pts/3 00:00:00 /tmp/go-build915599032/command-line-arguments/_obj/exe/analyze
root 695 675 696 0 4 06:10 pts/3 00:00:00 /tmp/go-build915599032/command-line-arguments/_obj/exe/analyze
root 695 675 697 0 4 06:10 pts/3 00:00:00 /tmp/go-build915599032/command-line-arguments/_obj/exe/analyze
root 695 675 698 0 4 06:10 pts/3 00:00:00 /tmp/go-build915599032/command-line-arguments/_obj/exe/analyze
root 709 146 709 0 1 06:11 pts/2 00:00:00 grep --color=auto analyze
strace를 이용하여 각각 어떤식으로 내부에서 작동하고 있는지 확인해보자.
[root@go_practice code]# strace -p 675
strace: Process 675 attached
waitid(P_PID, 695, ^Cstrace: Process 675 detached
<detached ...>
[root@go_practice code]# strace -p 676
strace: Process 676 attached
restart_syscall(<... resuming interrupted futex ...>^Cstrace: Process 676 detached
<detached ...>
[root@go_practice code]# strace -p 677
strace: Process 677 attached
epoll_wait(4, ^Cstrace: Process 677 detached
<detached ...>
[root@go_practice code]# strace -p 678
strace: Process 678 attached
futex(0xb05b80, FUTEX_WAIT, 0, NULL^Cstrace: Process 678 detached
<detached ...>
[root@go_practice code]# strace -p 679
strace: Process 679 attached
futex(0xc420194538, FUTEX_WAIT, 0, NULL^Cstrace: Process 679 detached
<detached ...>
[root@go_practice code]# strace -p 680
strace: attach: ptrace(PTRACE_ATTACH, ...): No such process
[root@go_practice code]# strace -p 686
strace: Process 686 attached
futex(0xc4202f7938, FUTEX_WAIT, 0, NULL^Cstrace: Process 686 detached
<detached ...>
먼저 run 명령어로 실행된 LWP들을 strace로 내부에서 어떤 동작을 하고있는지 확인해보았다.
내부에서 어떻게 동작하는지는 잘 모르겠으나 각기 프로세스에서 호출하는 함수들을 호출하며 대기하고 있었다.
waitid(), restart_syscall(), epoll_wait(), futex(FUTEX_WAIT)
kill 명령을 통해서 프로세스를 죽이면 실제 실행되고있는 /tmp/go-build LWP 들은 죽지 않고 계속해서 실행된다.
^C 신호를 줘도 계속해서 실행되며 kill 명령어를 통해 프로세스 들 중 아무거나 하나 죽이면 연달아서 전부다 죽었다.
[root@go_practice code] ps -efL | grep analyze
root 695 675 695 0 4 06:10 pts/3 00:00:00 /tmp/go-build915599032/command-line-arguments/_obj/exe/analyze
root 695 675 696 0 4 06:10 pts/3 00:00:00 /tmp/go-build915599032/command-line-arguments/_obj/exe/analyze
root 695 675 697 0 4 06:10 pts/3 00:00:00 /tmp/go-build915599032/command-line-arguments/_obj/exe/analyze
root 695 675 698 0 4 06:10 pts/3 00:00:00 /tmp/go-build915599032/command-line-arguments/_obj/exe/analyze
root 709 146 709 0 1 06:11 pts/2 00:00:00 grep --color=auto analyze
go run의 프로세스는 go-build의 프로세스들에게 사용자 signal을 전달하는 용도인 듯 하다.
[root@go_practice code]# strace -p 695
strace: Process 695 attached
restart_syscall(<... resuming interrupted futex ...>) = -1 ETIMEDOUT (Connection timed out)
futex(0x53bd38, FUTEX_WAKE, 1) = 1
futex(0x53bc70, FUTEX_WAKE, 1) = 1
futex(0xc42002a938, FUTEX_WAKE, 1) = 1
futex(0x53bb40, FUTEX_WAIT, 0, {0, 997351284} = -1 ETIMEOUT # 여기서 FUTEX_WAIT 하다가 ETIMEOUT이 들어오면 3개의 process를 FUTEX_WAKE시키고 FUTEX_WAIT한다.
^Cstrace: Process 695 detached
<detached ...>
[root@go_practice code]# strace -p 696
strace: Process 696 attached
restart_syscall(<... resuming interrupted futex ...>) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x53bd38, FUTEX_WAIT, 0, {60, 0} # 여기서 대기하다가 pselect6() 의 timeout의 신호를 받고 WAIT을 반복
^Cstrace: Process 696 detached
<detached ...>
[root@go_practice code]# strace -p 697
strace: Process 697 attached
futex(0xc42002a538, FUTEX_WAIT, 0, NULL) = 0
futex(0xc42002a538, FUTEX_WAIT, 0, NULL) = 0
write(1, "hello world\n", 3) = 3 # 실제 출력
futex(0xc42002a538, FUTEX_WAIT, 0, NULL
^Cstrace: Process 697 detached
<detached ...>
[root@go_practice code]# strace -p 698
strace: Process 698 attached
futex(0xc42002a938, FUTEX_WAIT, 0, NULL
^Cstrace: Process 698 detached
<detached ...>
이번에는 실제 작동중인 프로세스를 strace로 찍어 보았다.
실제 출력하는 process는 pid 697임을 알 수 있고, 695는 최상위 프로세스로 하위 프로세스를 WAKE함을 알 수 있다.
간단하게 작동하는 구조를 파악했으니 좀더 나아가서 goroutine과 net.http 패키지를 이용해서 확인해보자
net.http
go에서 기본적으로 지원하는 패키지인 net.http를 통하여 내부에서 어떤식으로 동작하는지 확인해보자.
package main
import (
"fmt"
"net/http"
"runtime"
"time"
)
func main() {
runtime.GOMAXPROCS(1)
url_list := make(map[string]int)
url_list["http://www.naver.com"] = 0
t := time.NewTicker(time.Second * 5)
for {
select {
case <-t.C:
for url := range url_list {
go scan(url)
}
}
}
return
}
func scan(url string) {
tr := &http.Transport{
MaxIdleConns: 10,
IdleConnTimeout: 30 * time.Second,
DisableCompression: true,
}
client := &http.Client{Transport: tr}
resp, err := client.Get(url)
if err != nil {
fmt.Println(err.Error())
}
fmt.Println(resp)
}
[root@go_practice code]# ps -efL | grep go
root 469 78 469 0 6 05:50 pts/0 00:00:00 go run http_scan.go
root 469 78 470 0 6 05:50 pts/0 00:00:00 go run http_scan.go
root 469 78 471 0 6 05:50 pts/0 00:00:00 go run http_scan.go
root 469 78 472 0 6 05:50 pts/0 00:00:00 go run http_scan.go
root 469 78 473 0 6 05:50 pts/0 00:00:00 go run http_scan.go
root 469 78 474 0 6 05:50 pts/0 00:00:00 go run http_scan.go
root 490 469 490 0 5 05:50 pts/0 00:00:00 /tmp/go-build622208802/command-line-arguments/_obj/exe/http_scan
root 490 469 491 0 5 05:50 pts/0 00:00:00 /tmp/go-build622208802/command-line-arguments/_obj/exe/http_scan
root 490 469 492 0 5 05:50 pts/0 00:00:00 /tmp/go-build622208802/command-line-arguments/_obj/exe/http_scan
root 490 469 493 0 5 05:50 pts/0 00:00:00 /tmp/go-build622208802/command-line-arguments/_obj/exe/http_scan
root 490 469 500 0 5 05:51 pts/0 00:00:00 /tmp/go-build622208802/command-line-arguments/_obj/exe/http_scan
root 511 234 511 0 1 05:51 pts/3 00:00:00 grep --color=auto go
[root@go_practice code]# strace -p 490
strace: Process 490 attached
futex(0x7bcc38, FUTEX_WAIT, 0, NULL) = 0
openat(AT_FDCWD, "/proc/sys/kernel/hostname", O_RDONLY|O_CLOEXEC) = 7
futex(0x7bc438, FUTEX_WAKE, 1) = 1
epoll_ctl(4, EPOLL_CTL_ADD, 7, {EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLET, {u32=3482427056, u64=140453207973552}}) = 0
fcntl(7, F_GETFL) = 0x8000 (flags O_RDONLY|O_LARGEFILE)
fcntl(7, F_SETFL, O_RDONLY|O_NONBLOCK|O_LARGEFILE) = 0
read(7, "go_practice\n", 512) = 12
epoll_ctl(4, EPOLL_CTL_DEL, 7, 0xc4205418dc) = 0
close(7) = 0
socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 7
setsockopt(7, SOL_SOCKET, SO_BROADCAST, [1], 4) = 0
futex(0x7bcc38, FUTEX_WAIT, 0, NULL) = 0
connect(7, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.11")}, 16) = 0
epoll_ctl(4, EPOLL_CTL_ADD, 7, {EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLET, {u32=3482425136, u64=140453207971632}}) = 0
getsockname(7, {sa_family=AF_INET, sin_port=htons(46365), sin_addr=inet_addr("127.0.0.1")}, [16]) = 0
getpeername(7, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.11")}, [16]) = 0
write(7, "O7\1\0\0\1\0\0\0\0\0\0\3www\5naver\3com\0\0\34\0\1", 31) = 31
futex(0x7bcc38, FUTEX_WAIT, 0, NULL
^Cstrace: Process 490 detached
<detached ...>
#include <fcntl.h>
int openat(int dirfd, const char *pathname, int flags);
int openat(int dirfd, const char *pathname, int flags, mode_t mode);
#include <sys/epoll.h>
int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);
#include <unistd.h>
#include <fcntl.h>
int fcntl(int fd, int cmd, ... /* arg */ );
#include <unistd.h>
ssize_t read(int fd, void *buf, size_t count);
#include <unistd.h>
int close(int fd);
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
int socket(int domain, int type, int protocol);
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
int getsockopt(int sockfd, int level, int optname,
void* optval,socklen_t *optlen);
int setsockopt(int sockfd, int level, int optname,
const void *optval, socklen_t optlen);
[root@go_practice code]# strace -p 491
strace: Process 491 attached
restart_syscall(<... resuming interrupted futex ...>) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
sched_yield() = 0
futex(0x7bc370, FUTEX_WAIT, 2, NULL) = 0
futex(0x7bc370, FUTEX_WAKE, 1) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
sched_yield() = 0
futex(0x7bc370, FUTEX_WAKE, 1) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
sched_yield() = 0
futex(0x7bc370, FUTEX_WAIT, 2, NULL) = 0
futex(0x7bc370, FUTEX_WAKE, 1) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
sched_yield() = 0
futex(0x7bc370, FUTEX_WAIT, 2, NULL) = 0
futex(0x7bc370, FUTEX_WAKE, 1) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
sched_yield() = 0
futex(0x7bc370, FUTEX_WAIT, 2, NULL) = 0
futex(0x7bc370, FUTEX_WAKE, 1) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
sched_yield() = 0
futex(0x7bc370, FUTEX_WAIT, 2, NULL) = 0
futex(0x7bc370, FUTEX_WAKE, 1) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = -1 EAGAIN (Resource temporarily unavailable)
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}) = 0
pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
futex(0x7bc438, FUTEX_WAIT, 0, {60, 0}
^Cstrace: Process 491 detached
<detached ...>
[root@go_practice code]# strace -p 492
strace: Process 492 attached
futex(0xc42002c938, FUTEX_WAIT, 0, NULL) = 0
openat(AT_FDCWD, "/proc/sys/kernel/hostname", O_RDONLY|O_CLOEXEC) = 7
futex(0x7bc438, FUTEX_WAKE, 1) = 1
futex(0x7bc370, FUTEX_WAKE, 1) = 1
epoll_ctl(4, EPOLL_CTL_ADD, 7, {EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLET, {u32=3482425712, u64=140453207972208}}) = 0
fcntl(7, F_GETFL) = 0x8000 (flags O_RDONLY|O_LARGEFILE)
fcntl(7, F_SETFL, O_RDONLY|O_NONBLOCK|O_LARGEFILE) = 0
futex(0xc42002c938, FUTEX_WAIT, 0, NULL^Cstrace: Process 492 detached
<detached ...>
[root@go_practice code]# strace -p 493
strace: Process 493 attached
epoll_wait(4, [{EPOLLIN|EPOLLOUT, {u32=3482426864, u64=140453207973360}}], 128, -1) = 1
epoll_wait(4, [{EPOLLOUT, {u32=3482426864, u64=140453207973360}}], 128, -1) = 1
epoll_wait(4, [{EPOLLOUT, {u32=3482424560, u64=140453207971056}}], 128, -1) = 1
epoll_wait(4, [{EPOLLIN|EPOLLOUT, {u32=3482426864, u64=140453207973360}}], 128, -1) = 1
epoll_wait(4, [{EPOLLOUT, {u32=3482424560, u64=140453207971056}}], 128, -1) = 1
epoll_wait(4, [{EPOLLIN|EPOLLOUT, {u32=3482424560, u64=140453207971056}}], 128, -1) = 1
futex(0x7bc438, FUTEX_WAKE, 1) = 1
read(11, "q\1\201\200\0\1\0\3\0\0\0\0\3www\5naver\3com\0\0\1\0\1\300"..., 512) = 97
epoll_ctl(4, EPOLL_CTL_DEL, 11, 0xc420036b14) = 0
close(11) = 0
socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 5
setsockopt(5, SOL_SOCKET, SO_BROADCAST, [1], 4) = 0
connect(5, {sa_family=AF_INET, sin_port=htons(9), sin_addr=inet_addr("210.89.164.90")}, 16) = 0
epoll_ctl(4, EPOLL_CTL_ADD, 5, {EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLET, {u32=3482424560, u64=140453207971056}}) = 0
getsockname(5, {sa_family=AF_INET, sin_port=htons(46349), sin_addr=inet_addr("172.18.0.2")}, [16]) = 0
getpeername(5, {sa_family=AF_INET, sin_port=htons(9), sin_addr=inet_addr("210.89.164.90")}, [16]) = 0
epoll_ctl(4, EPOLL_CTL_DEL, 5, 0xc4200379ac) = 0
close(5) = 0
socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 5
setsockopt(5, SOL_SOCKET, SO_BROADCAST, [1], 4) = 0
connect(5, {sa_family=AF_INET, sin_port=htons(9), sin_addr=inet_addr("125.209.222.141")}, 16) = 0
epoll_ctl(4, EPOLL_CTL_ADD, 5, {EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLET, {u32=3482424560, u64=140453207971056}}) = 0
getsockname(5, {sa_family=AF_INET, sin_port=htons(46987), sin_addr=inet_addr("172.18.0.2")}, [16]) = 0
getpeername(5, {sa_family=AF_INET, sin_port=htons(9), sin_addr=inet_addr("125.209.222.141")}, [16]) = 0
epoll_ctl(4, EPOLL_CTL_DEL, 5, 0xc4200379ac) = 0
close(5) = 0
socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 5
setsockopt(5, SOL_SOCKET, SO_BROADCAST, [1], 4) = 0
connect(5, {sa_family=AF_INET, sin_port=htons(80), sin_addr=inet_addr("210.89.164.90")}, 16) = -1 EINPROGRESS (Operation now in progress)
epoll_ctl(4, EPOLL_CTL_ADD, 5, {EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLET, {u32=3482424560, u64=140453207971056}}) = 0
epoll_wait(4, [], 128, 0) = 0
epoll_wait(4, [{EPOLLOUT, {u32=3482424560, u64=140453207971056}}], 128, -1) = 1
futex(0x7bc438, FUTEX_WAKE, 1) = 1
getsockopt(5, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
getpeername(5, {sa_family=AF_INET, sin_port=htons(80), sin_addr=inet_addr("210.89.164.90")}, [16]) = 0
getsockname(5, {sa_family=AF_INET, sin_port=htons(37270), sin_addr=inet_addr("172.18.0.2")}, [16]) = 0
setsockopt(5, SOL_TCP, TCP_NODELAY, [1], 4) = 0
read(5, 0xc420352000, 4096) = -1 EAGAIN (Resource temporarily unavailable)
write(5, "GET / HTTP/1.1\r\nHost: www.naver."..., 71) = 71
epoll_wait(4, [], 128, 0) = 0
epoll_wait(4, [{EPOLLIN|EPOLLOUT, {u32=3482424560, u64=140453207971056}}], 128, -1) = 1
futex(0x7bc438, FUTEX_WAKE, 1) = 1
futex(0x7bc370, FUTEX_WAKE, 1) = 1
read(5, "HTTP/1.1 302 Moved Temporarily\r\n"..., 4096) = 394
futex(0x7bc438, FUTEX_WAKE, 1) = 1
read(5, "", 4096) = 0
epoll_ctl(4, EPOLL_CTL_DEL, 5, 0xc42003797c) = 0
close(5) = 0
futex(0xc42002cd38, FUTEX_WAIT, 0, NULL^Cstrace: Process 493 detached
<detached ...>
[root@go_practice code]# strace -p 500
strace: Process 500 attached
restart_syscall(<... resuming interrupted futex ...>) = -1 ETIMEDOUT (Connection timed out)
futex(0x7bc438, FUTEX_WAKE, 1) = 1
futex(0x7bc370, FUTEX_WAKE, 1) = 1
futex(0xc42002c938, FUTEX_WAKE, 1) = 1
futex(0x7bc0a0, FUTEX_WAIT, 0, {0, 71946313}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7bc438, FUTEX_WAKE, 1) = 1
futex(0x7bc370, FUTEX_WAKE, 1) = 1
futex(0xc42002d538, FUTEX_WAKE, 1) = 1
futex(0x7bc0a0, FUTEX_WAIT, 0, {4, 915189303}^Cstrace: Process 500 detached
<detached ...>
[root@go_practice code]# clear
[root@go_practice code]# strace -p 636
strace: Process 636 attached
epoll_wait(4, [{EPOLLOUT, {u32=3482427056, u64=140453207973552}}], 128, -1) = 1
epoll_wait(4, [{EPOLLOUT, {u32=3482426096, u64=140453207972592}}], 128, -1) = 1
epoll_wait(4, [{EPOLLIN|EPOLLOUT, {u32=3482426096, u64=140453207972592}}, {EPOLLIN|EPOLLOUT, {u32=3482427056, u64=140453207973552}}], 128, -1) = 2
futex(0x7bc438, FUTEX_WAKE, 1) = 1
futex(0x7bc370, FUTEX_WAKE, 1) = 1
read(10, "d7\201\203\0\1\0\0\0\0\0\0\3www\5naver\3com\0\0\34\0\1", 512) = 31
epoll_ctl(4, EPOLL_CTL_DEL, 10, 0xc420037b14) = 0
close(10) = 0
read(11, ";e\201\200\0\1\0\3\0\0\0\0\3www\5naver\3com\0\0\1\0\1\300"..., 512) = 97
epoll_ctl(4, EPOLL_CTL_DEL, 11, 0xc420039b14) = 0
close(11) = 0
socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 10
setsockopt(10, SOL_SOCKET, SO_BROADCAST, [1], 4) = 0
connect(10, {sa_family=AF_INET, sin_port=htons(9), sin_addr=inet_addr("210.89.164.90")}, 16) = 0
epoll_ctl(4, EPOLL_CTL_ADD, 10, {EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLET, {u32=3482426096, u64=140453207972592}}) = 0
getsockname(10, {sa_family=AF_INET, sin_port=htons(50175), sin_addr=inet_addr("172.18.0.2")}, [16]) = 0
getpeername(10, {sa_family=AF_INET, sin_port=htons(9), sin_addr=inet_addr("210.89.164.90")}, [16]) = 0
epoll_ctl(4, EPOLL_CTL_DEL, 10, 0xc4203f59ac) = 0
close(10) = 0
futex(0xc42002d538, FUTEX_WAIT, 0, NULL) = 0
write(6, "\25\3\3\0\32\0\0\0\0\0\0\0\4\376\214\257|\315\v\334\37\325\246%3\30\1Xi\360L", 31) = 31
epoll_ctl(4, EPOLL_CTL_DEL, 6, 0xc4203f26ac) = 0
close(6) = 0
futex(0xc42002d538, FUTEX_WAIT, 0, NULL^Cstrace: Process 636 detached
<detached ...>