Hello,
I got a "memcached-1.4.20 stuck" problem when EMFILE happen.
Here are my memcached's cmdline "memcached -s /xxx/mc_usock.11201 -c 1024
-m 4000 -f 1.05 -o slab_automove -o slab_reassign -t 1 -p 11201".
cat /proc/version
Linux version 2.6.32-358.el6.x86_64
([email protected]) (gcc version 4.4.7 20120313
(Red Hat 4.4.7-3) (GCC) ) #1 SMP Tue Jan 29 11:47:41 EST 2013
memcached-1.4.20 stuck and don't work any more when it runs for a period
of time.
Here are some information for gdb:
(gdb) p stats
$2 = {mutex = {__data = {__lock = 0, __count = 0, __owner = 0, __kind =
0, __nusers = 0, {__spins = 0,
__list = {__next = 0x0}}}, __size = '\000' <repeats 23 times>,
__align = 0}, curr_items = 149156,
total_items = 9876811, curr_bytes = 3712501870,* curr_conns = 5*,
total_conns = 39738, rejected_conns = 0,
malloc_fails = 0, *reserved_fds = 5*, *conn_structs = 1012*, get_cmds =
0, set_cmds = 0, touch_cmds = 0,
get_hits = 0, get_misses = 0, touch_hits = 0, touch_misses = 0, evictions
= 0, reclaimed = 0,
started = 0, *accepting_conns = false*, *listen_disabled_num = 1*,
hash_power_level = 17,
hash_bytes = 524288, hash_is_expanding = false, expired_unfetched = 0,
evicted_unfetched = 0,
slab_reassign_running = false, slabs_moved = 20, lru_crawler_running =
false,
disable_write_by_exptime = 0, disable_write_by_length = 0,
disable_write_by_access = 0,
evicted_write_reply_timeout_times = 0}
(gdb) p allow_new_conns
$4 = false
And I found that "allow_new_conns" just set to false when "accept" failed
and errno is "EMFILE".
Here are the codes:
static void drive_machine(conn *c) {
……
} else if (errno == EMFILE) {
if (settings.verbose > 0)
fprintf(stderr, "Too many open connections\n");
* accept_new_conns(false);*
stop = true;
} else {
……
}
If I change the flag "allow_new_conns", it can work again. As below:
*(gdb) set allow_new_conns=1*
(gdb) p allow_new_conns
$5 = true
(gdb) c
Continuing.
I know that "allow_new_conns" will be set to "true" when "conn_close"
called. But how could it happen for the case that when "accept" failed ,
and errno is "EMFILE", and this connection is the only one for accepting.
Notes that *curr_conns = 5.*
Not run out of fd:
ls /proc/1748(memcached_pid)/fd | wc -l
17
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