pgpool-II3.1 的内存泄漏（五）

磨砺技术珠矶，践行数据之道，追求卓越价值

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[作者高健@博客园 luckyjackgao@gmail.com]

情形B read_startup_packet 调用 calloc

==27927== 594 (528 direct, 66 indirect) bytes in 11 blocks are definitely lost in loss record 85 of 100

==27927== at 0x4A05140: calloc (vg_replace_malloc.c:418)

==27927== by 0x40895B: read_startup_packet (child.c:803)

==27927== by 0x409663: do_child (child.c:210)

==27927== by 0x403F04: fork_a_child (main.c:1073)

==27927== by 0x406C00: main (main.c:550)

从上述log可知, 调用关系如下：

main-> fork_a_child -> do_child -> read_startup_packet -> calloc

以下是各个函数的主要相关逻辑：

main函数：

复制代码

* pgpool main program

int main(int argc, char **argv)

{

……

* We need to block signal here. Otherwise child might send some

* signals, for example SIGUSR1(fail over). Children will inherit

* signal blocking but they do unblock signals at the very beginning

* of process. So this is harmless.

POOL_SETMASK(&BlockSig);

/* fork the children */

for (i=0;i<pool_config->num_init_children;i++)

{

process_info[i].pid = fork_a_child(unix_fd, inet_fd, i);

process_info[i].start_time = time(NULL);

}

/* set up signal handlers */

pool_signal(SIGTERM, exit_handler);

pool_signal(SIGINT, exit_handler);

pool_signal(SIGQUIT, exit_handler);

pool_signal(SIGCHLD, reap_handler);

pool_signal(SIGUSR1, failover_handler);

pool_signal(SIGUSR2, wakeup_handler);

pool_signal(SIGHUP, reload_config_handler);

/* create pipe for delivering event */

if (pipe(pipe_fds) < 0)

{

pool_error("failed to create pipe");

myexit(1);

}

……

* This is the main loop

for (;;)

{

……

}

pool_shmem_exit(0);

}

复制代码

for_a_child函数：

复制代码

* fork a child

pid_t fork_a_child(int unix_fd, int inet_fd, int id)

{

pid_t pid;

pid = fork();

if (pid == 0)

{

/* Before we unconditionally closed pipe_fds[0] and pipe_fds[1]

* here, which is apparently wrong since in the start up of

* pgpool, pipe(2) is not called yet and it mistakenly closes

* fd 0. Now we check the fd > 0 before close(), expecting

* pipe returns fds greater than 0. Note that we cannot

* unconditionally remove close(2) calls since fork_a_child()

* may be called *after* pgpool starting up.

if (pipe_fds[0] > 0)

{

close(pipe_fds[0]);

close(pipe_fds[1]);

}

myargv = save_ps_display_args(myargc, myargv);

/* call child main */

POOL_SETMASK(&UnBlockSig);

reload_config_request = 0;

my_proc_id = id;

run_as_pcp_child = false;

do_child(unix_fd, inet_fd);

}

else if (pid == -1)

{

pool_error("fork() failed. reason: %s", strerror(errno));

myexit(1);

}

return pid;

}

复制代码

do_child函数：

复制代码

* child main loop

void do_child(int unix_fd, int inet_fd)

{

……

for (;;){

StartupPacket *sp;

……

/* perform accept() */

frontend = do_accept(unix_fd, inet_fd, &timeout);

……

/* read the startup packet */

retry_startup:

sp = read_startup_packet(frontend);

if (sp == NULL){

/* failed to read the startup packet. return to the accept() loop */

pool_close(frontend);

connection_count_down();

continue;

}

……

* Ok, negotiaton with frontend has been done. Let's go to the

* next step. Connect to backend if there's no existing

* connection which can be reused by this frontend.

* Authentication is also done in this step.

……

/* query process loop */

for (;;){

……

}

/* Destroy session context */

pool_session_context_destroy();

/* Mark this connection pool is not conncted from frontend */

pool_coninfo_unset_frontend_connected

(pool_get_process_context()->proc_id, pool_pool_index());

accepted = 0;

connection_count_down();

timeout.tv_sec = pool_config->child_life_time;

timeout.tv_usec = 0;

/* increment queries counter if necessary */

if ( pool_config->child_max_connections > 0 )

connections_count++;

/* check if maximum connections count for this child reached */

if ( ( pool_config->child_max_connections > 0 ) &&

( connections_count >= pool_config->child_max_connections ) ){

pool_log("child exiting, %d connections reached",

pool_config->child_max_connections);

send_frontend_exits();

child_exit(2);

}

child_exit(0);

}

复制代码

read_startup_packet 函数:

复制代码

* Read startup packet

* Read the startup packet and parse the contents.

static StartupPacket *read_startup_packet(POOL_CONNECTION *cp)

{

StartupPacket *sp;

……

sp = (StartupPacket *)calloc(sizeof(*sp), 1);

if (!sp)

{

pool_error("read_startup_packet: out of memory");

return NULL;

}

……

sp->startup_packet = calloc(len, 1);

if (!sp->startup_packet)

{

pool_error("read_startup_packet: out of memory");

pool_free_startup_packet(sp);

alarm(0);

pool_signal(SIGALRM, SIG_IGN);

return NULL;

}

……

switch(sp->major)

{

case PROTO_MAJOR_V2: /* V2 */

sp2 = (StartupPacket_v2 *)(sp->startup_packet);

sp->database = calloc(SM_DATABASE+1, 1);

if (!sp->database)

{

pool_error("read_startup_packet: out of memory");

pool_free_startup_packet(sp);

alarm(0);

pool_signal(SIGALRM, SIG_IGN);

return NULL;

}

……

break;

case 1234: /* cancel or SSL request */

/* set dummy database, user info */

sp->database = calloc(1, 1);

if (!sp->database)

{

pool_error("read_startup_packet: out of memory");

pool_free_startup_packet(sp);

alarm(0);

pool_signal(SIGALRM, SIG_IGN);

return NULL;

}

sp->user = calloc(1, 1);

if (!sp->user)

{

pool_error("read_startup_packet: out of memory");

pool_free_startup_packet(sp);

alarm(0);

pool_signal(SIGALRM, SIG_IGN);

return NULL;

}

break;

default:

pool_error("read_startup_packet: invalid major no: %d", sp->major);

pool_free_startup_packet(sp);

alarm(0);

pool_signal(SIGALRM, SIG_IGN);

return NULL;

}

pool_debug("Protocol Major: %d Minor: %d database: %s user: %s",

sp->major, sp->minor, sp->database, sp->user);

alarm(0);

pool_signal(SIGALRM, SIG_IGN);

return sp;

}

复制代码

由以上各个函数的逻辑，可以看到

在 read_startup_packet 函数中，调用 calloc 来开了内存。

但是在do_child 函数的主循环中，会反复使用 read_startup_packet 函数，并且也未能释放内存。

由于 do_child 函数的反复循环，就会反复开内存而不释放。

这里确确实实地发生了内存泄露。

其实，它的do_child函数的循环的末尾，应该释放 StartupPacket *sp 才好，不知为何不去释放。

[作者高健@博客园 luckyjackgao@gmail.com]

回到上一级页面： PostgreSQL集群方案相关索引页回到顶级页面：PostgreSQL索引页

磨砺技术珠矶，践行数据之道，追求卓越价值

本文转自健哥的数据花园博客园博客，原文链接：http://www.cnblogs.com/gaojian/archive/2012/08/21/2649065.html，如需转载请自行联系原作者

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