Mysql – Allowed Memory Size Exhausted irregardless of amount, Memory leak

apache-2.2memory leakMySQLWordpress

I'm running a small WordPress blog for my sister on a very common CentOS 5.11 with Apache 2 and PHP 5.3.3.

Lately, we discovered while she tried to update or install anything using WordPress own interface it all stalled, and I found this:

PHP Fatal error:  Allowed memory size of 268435456 bytes exhausted (tried to allocate 20 bytes) in /var/www/foobar/wp-admin/includes/file.php on line 159, referer: http://foobar.com/wp-admin/update-core.php?action=do-core-upgrade

After searching for a bit the easiest thing seemed to be to just raise the memory limit a bit, but irregardless of how much I raise it to it basically just takes longer for it to hit this roof.

Here's some excerpts:

512M

PHP Fatal error:  Allowed memory size of 536870912 bytes exhausted (tried to allocate 261900 bytes) in /var/www/foobar/wp-admin/includes/file.php on line 159, referer: http://foobar.com/wp-admin/update-core.php?action=do-core-upgrade

1024M

PHP Fatal error:  Allowed memory size of 1073741824 bytes exhausted (tried to allocate 261900 bytes) in /var/www/foobar/wp-admin/includes/file.php on line 159, referer: http://foobar.com/wp-admin/update-core.php?action=do-core-upgrade

This is all configured using both …

memory_limit = 1024M

in /etc/php.ini as well as …

define('WP_MEMORY_LIMIT', '1024M');
            } else {
                    define('WP_MEMORY_LIMIT', '1024M');
            }
    }

    if ( ! defined( 'WP_MAX_MEMORY_LIMIT' ) ) {
            define( 'WP_MAX_MEMORY_LIMIT', '1024M' );
    }

in ~/wp-includes/default-constants.php.

This obviously leads me to believe there's a memory leak somewhere which have to be solved, but how would I go about to find this when everything's prepackaged WordPress stuff? Here's some excerpts from top ^M when pushing the Update button:

Before

Mem:   1034656k total,   235836k used,   798820k free,     6388k buffers
Swap:  2048248k total,   107940k used,  1940308k free,   139156k cached

PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
23649 apache    19   0  160m  22m  15m S  0.0  2.2   0:07.06 httpd

While

Mem:   1034656k total,  1020396k used,    14260k free,       60k buffers
Swap:  2048248k total,   152484k used,  1895764k free,    26880k cached

PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
23645 apache    21   0 1079m 906m  16m R 75.5 89.7   0:06.95 httpd

WordPress version 4.2

MySQL 5.1

Apache 2.2.22

Installed plugins: Hello Dolly 1.6 and Akismet 3.1.1

This is the output from strace -f -r exactly where it stalls:

29638 0.000134 writev(16, [{"28\r\n", 4}, {"<p>Enabling Maintenance mode&#82"..., 40}, {"\r\n", 2}], 3) = 46
29638 0.000122 time(NULL) = 1436025429
29638 0.000060 getcwd("/var/www/foobar/wp-admin"..., 4096) = 32
29638 0.000064 time(NULL) = 1436025429
29638 0.000040 open("/tmp/php9Ldioo", O_RDWR|O_CREAT|O_EXCL, 0600) = 19
29638 0.000061 getpeername(18, {sa_family=AF_INET, sin_port=htons(21), sin_addr=inet_addr("127.0.0.1")}, [16]) = 0
29638 0.000068 poll([{fd=18, events=POLLOUT}], 1, 240000) = 1 ([{fd=18, revents=POLLOUT}])
29638 0.000038 send(18, "PASV\r\n", 6, 0) = 6
29638 0.000078 poll([{fd=18, events=POLLIN|POLLERR|POLLHUP}], 1, 240000) = 1 ([{fd=18, revents=POLLIN}])
29638 0.000119 recv(18, "227 Entering Passive Mode (127,0"..., 4096, 0) = 45
29638 0.000048 socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 20
29638 0.000029 fcntl64(20, F_GETFL) = 0x2 (flags O_RDWR)
29638 0.000025 fcntl64(20, F_SETFL, O_RDWR|O_NONBLOCK) = 0
29638 0.000026 connect(20, {sa_family=AF_INET, sin_port=htons(8721), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now in progress)
29638 0.000060 poll([{fd=20, events=POLLIN|POLLOUT|POLLERR|POLLHUP}], 1, 240000) = 1 ([{fd=20, revents=POLLOUT}])
29638 0.000039 getsockopt(20, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
29638 0.000028 fcntl64(20, F_SETFL, O_RDWR) = 0
29638 0.000024 poll([{fd=18, events=POLLOUT}], 1, 240000) = 1 ([{fd=18, revents=POLLOUT}])
29638 0.000036 send(18, "NLST /.maintenance\r\n", 20, 0) = 20
29638 0.000053 poll([{fd=18, events=POLLIN|POLLERR|POLLHUP}], 1, 240000) = 1 ([{fd=18, revents=POLLIN}])
29638 0.000187 recv(18, "150 Here comes the directory lis"..., 4096, 0) = 39
29638 0.000111 poll([{fd=20, events=POLLIN|POLLERR|POLLHUP}], 1, 240000) = 1 ([{fd=20, revents=POLLIN}])
29638 0.000037 recv(20, "", 4096, 0) = 0
29638 0.000024 close(20) = 0
29638 0.000038 lseek(19, 0, SEEK_SET) = 0
29638 0.000026 read(19, "", 8192) = 0
29638 0.000031 close(19) = 0
29638 0.000023 unlink("/tmp/php9Ldioo") = 0
29638 0.000042 poll([{fd=18, events=POLLIN|POLLERR|POLLHUP}], 1, 240000) = 1 ([{fd=18, revents=POLLIN}])
29638 0.000037 recv(18, "226 Directory send OK.\r\n", 4096, 0) = 24
29638 0.000063 poll([{fd=18, events=POLLOUT}], 1, 240000) = 1 ([{fd=18, revents=POLLOUT}])
29638 0.000038 send(18, "CWD /.maintenance/\r\n", 20, 0) = 20
29638 0.000035 poll([{fd=18, events=POLLIN|POLLERR|POLLHUP}], 1, 240000) = 1 ([{fd=18, revents=POLLIN}])
29638 0.000067 recv(18, "550 Failed to change directory.\r"..., 4096, 0) = 33
29638 0.000050 poll([{fd=18, events=POLLOUT}], 1, 240000) = 1 ([{fd=18, revents=POLLOUT}])
29638 0.000037 send(18, "PWD\r\n", 5, 0) = 5
29638 0.000052 poll([{fd=18, events=POLLIN|POLLERR|POLLHUP}], 1, 240000) = 1 ([{fd=18, revents=POLLIN}])
29638 0.000035 recv(18, "257 \"/\"\r\n", 4096, 0) = 9
29638 0.000047 poll([{fd=18, events=POLLOUT}], 1, 240000) = 1 ([{fd=18, revents=POLLOUT}])
29638 0.000036 send(18, "RMD /.maintenance\r\n", 19, 0) = 19
29638 0.000059 poll([{fd=18, events=POLLIN|POLLERR|POLLHUP}], 1, 240000) = 1 ([{fd=18, revents=POLLIN}])
29638 0.000035 recv(18, "550 Remove directory operation f"..., 4096, 0) = 40
29638 0.002773 brk(0x929f000) = 0x929f000
29638 0.001533 brk(0x92df000) = 0x92df000
29638 0.001396 brk(0x931f000) = 0x931f000
29638 0.001436 brk(0x935f000) = 0x935f000
29638 0.001488 brk(0x939f000) = 0x939f000
29638 0.001460 brk(0x93df000) = 0x93df000
29638 0.001388 brk(0x941f000) = 0x941f000
29638 0.001452 brk(0x945f000) = 0x945f000
29638 0.000772 brk(0x949f000) = 0x949f000
29638 0.000668 brk(0x94df000) = 0x94df000
29638 0.001326 brk(0x951f000) = 0x951f000
29638 0.001320 brk(0x955f000) = 0x955f000
29638 0.001423 brk(0x959f000) = 0x959f000
29638 0.001508 brk(0x95df000) = 0x95df000
29638 0.001410 brk(0x961f000) = 0x961f000
29638 0.000280 brk(0x965f000) = 0x965f000
/29638 0.001073 brk(0x969f000) = 0x969f000
29638 0.001342 brk(0x96df000) = 0x96df000
29638 0.001341 brk(0x971f000) = 0x971f000
29638 0.001389 brk(0x975f000) = 0x975f000
29638 0.001385 brk(0x979f000) = 0x979f000
29638 0.001172 brk(0x97df000) = 0x97df000

Best Answer

It looks like an infinite loop as line 159 of wp-admin/includes/file.php is a recursive call to the function wp_tmpnam(). It breaks the update process, so may be it could be worth checking this small correction, which describes your problem : wordpress bug fix

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