Re: Lots of connections led oxenstored stuck

[Joe Jin <joe.jin@oracle.com>]

On 08/11/14 17:41, Dave Scott wrote:
> 
> On 11 Aug 2014, at 01:35, Joe Jin <joe.jin@oracle.com> wrote:
> 
>> On 08/08/14 17:37, Dave Scott wrote:
>>>
>>> On 8 Aug 2014, at 09:35, Liuqiming (John) <john.liuqiming@huawei.com> wrote:
>>>
>>>> In oxenstored it use "select" for incoming socket, so I don't think it can handle more than 1024 socket connections. 
>>>
>>> That’s true.
>>
>> The problem is when oxenstored does not respond any request anymore even all
>> thread exited, with my reproducer, when you executed it and all threads exited,
>> "xm list -l" will stuck.
> 
> OK so is this the behaviour you expect:
> 
> * root in dom0 opens many connections, until oxenstored is out of resources (where the most limited resource is currently file descriptors)
> * root in dom0 closes the connections
> * oxenstored recovers, and ‘xm list -l’ works again
> 
> Instead, you’re seeing oxenstored getting into a stuck state causing ‘xm list -l’ to block — is this accurate?

Yes that's it.

> 
> Could you share your reproducer program?

/* 
 * This program used to test oxenstored connections stuck issue.
 * please compile by below command:
 *	gcc -o client client.c -lpthread
 */
#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <string.h>
#include <pthread.h>
#include <stdlib.h>
#include <errno.h>


void *main_thread(void *arg)
{
	struct sockaddr_un address;
	int socket_fd, nbytes;
	char buffer[256];
	int i;
	extern int errno;

	memcpy(&i, arg, sizeof(i));
	socket_fd = socket(PF_UNIX, SOCK_STREAM, 0);
	if (socket_fd < 0) {
		fprintf(stderr, "socket() %dth failed, errno=%d\n", i, errno);
		return;
	}
	fprintf(stderr, "socket() %dth ok!\n", i);

	/* start with a clean address structure */
	memset(&address, 0, sizeof(struct sockaddr_un));

	address.sun_family = AF_UNIX;
	snprintf(address.sun_path, 1024, "/var/run/xenstored/socket");

	if (connect(socket_fd,
		    (struct sockaddr *) &address,
		    sizeof(struct sockaddr_un)) != 0) {
		fprintf(stderr, "connect() %d failed, error=%d", i, errno);
		return;
	}
	fprintf(stderr, "connec() %dth ok!\n", i);

	while (1)
		sleep(1);
	if (arg) {
		free(arg);
		arg = NULL;
	}

	return;
}

int main(void)
{
	int i;
	for (i = 0; i < 2000; i++) {
		void *arg = malloc(sizeof(i));
		memset(arg, 0, sizeof(i));
		memcpy(arg, &i, sizeof(i));
		pthread_t thread;
		if (pthread_create(&thread, NULL, main_thread, arg) != 0) {
			perror("pthread_create:");
			break;
		}
	}
	/* Wait all children exit */
	sleep(3);
	return 0;
}
/* end */