#40594 [NEW]: Blocking socket functions cause Apache freeze

[karldray at interchange dot ubc dot ca]

From: karldray at interchange dot ubc dot ca
Operating system: Windows XP
PHP version: 5.2.1
PHP Bug Type: Sockets related
Bug description: Blocking socket functions cause Apache freeze

Description:
------------
I have a PHP page that opens a UDP socket and listens for data (blocking
on socket_recvfrom). When the socket recieves a packet, the script echoes
a message and finishes. This works fine, but when two instances of this
page are running (both blocking on socket_recvfrom), Apache (2.2.4) stops
responding to any new requests (even for non-php pages) until one of them
gets unblocked. The same problem occurs with other blocking socket
functions (such as socket_accept and socket_read with TCP sockets).

Reproduction instructions:
1. open a browser window to udp_recv.php?port=11111. it sits there
"loading" since PHP is waiting for socket data.
2. open another browser window to udp_recv.php?port=22222.
3 (the problem). open another browser window and point it to index.html or
any other url on the server. it just sits there "loading".
4. in a command prompt, type "perl udp_send.pl 11111" to send 'hello' to
the first php script's udp socket, causing it to finish. Suddenly, the
third request completes.

Reproduce code:
---------------
udp_recv.php:

<?php
$listener = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_bind($listener, gethostbyname('localhost'), $_GET['port']) or
exit('error on bind');
$len = socket_recvfrom($listener, $data, 2048, 0, $host, $port);
echo "$len bytes recieved from $host:$port: $data\n";
?>

udp_send.pl:

use strict; use Socket;
socket(SOCKET, PF_INET, SOCK_DGRAM, getprotobyname('udp')) or die "socket:
$!";
send(SOCKET, 'hello', 0, sockaddr_in(shift, inet_aton('localhost'))) or
die "send: $!";


Expected result:
----------------
I expect Apache to continue to accept and handle new web page requests
while the two PHP pages are blocking on socket functions.

Actual result:
--------------
Once there are two PHP pages blocking on socket functions, all subsequent
requests (even for non-php URIs) appear as "loading" in the browser until
one of the PHP scripts unblocks.

Note: If the third request is for a PHP page containing an error_log() at
the very beginning, then the logfile output is not generated as long as
the first two pages are blocking (suggesting that Apache isn't getting
around to starting PHP during this time).

--
Edit bug report at [url]http://bugs.php.net/?id=40594&edit=1[/url]
--
Try a CVS snapshot (PHP 4.4): [url]http://bugs.php.net/fix.php?id=40594&r=trysnapshot44[/url]
Try a CVS snapshot (PHP 5.2): [url]http://bugs.php.net/fix.php?id=40594&r=trysnapshot52[/url]
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[karldray at interchange dot ubc dot ca]

ID: 40594
User updated by: karldray at interchange dot ubc dot ca
Reported By: karldray at interchange dot ubc dot ca
Status: Open
Bug Type: Sockets related
Operating System: Windows XP
PHP Version: 5.2.1
New Comment:

This turns out not to be specific to sockets or even to blocking
functions! I just realized that if I replace udp_recv.php with a
one-line script like
sleep(10);
or something like
for($i=0;$i<100000000;$i++);
then the same problem occurs: while two of them are running, apache
won't handle any new requests.


Previous Comments:
------------------------------------------------------------------------

[2007-02-22 16:39:34] karldray at interchange dot ubc dot ca

Description:
------------
I have a PHP page that opens a UDP socket and listens for data
(blocking on socket_recvfrom). When the socket recieves a packet, the
script echoes a message and finishes. This works fine, but when two
instances of this page are running (both blocking on socket_recvfrom),
Apache (2.2.4) stops responding to any new requests (even for non-php
pages) until one of them gets unblocked. The same problem occurs with
other blocking socket functions (such as socket_accept and socket_read
with TCP sockets).

Reproduction instructions:
1. open a browser window to udp_recv.php?port=11111. it sits there
"loading" since PHP is waiting for socket data.
2. open another browser window to udp_recv.php?port=22222.
3 (the problem). open another browser window and point it to index.html
or any other url on the server. it just sits there "loading".
4. in a command prompt, type "perl udp_send.pl 11111" to send 'hello'
to the first php script's udp socket, causing it to finish. Suddenly,
the third request completes.

Reproduce code:
---------------
udp_recv.php:

<?php
$listener = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_bind($listener, gethostbyname('localhost'), $_GET['port']) or
exit('error on bind');
$len = socket_recvfrom($listener, $data, 2048, 0, $host, $port);
echo "$len bytes recieved from $host:$port: $data\n";
?>

udp_send.pl:

use strict; use Socket;
socket(SOCKET, PF_INET, SOCK_DGRAM, getprotobyname('udp')) or die
"socket: $!";
send(SOCKET, 'hello', 0, sockaddr_in(shift, inet_aton('localhost'))) or
die "send: $!";


Expected result:
----------------
I expect Apache to continue to accept and handle new web page requests
while the two PHP pages are blocking on socket functions.

Actual result:
--------------
Once there are two PHP pages blocking on socket functions, all
subsequent requests (even for non-php URIs) appear as "loading" in the
browser until one of the PHP scripts unblocks.

Note: If the third request is for a PHP page containing an error_log()
at the very beginning, then the logfile output is not generated as long
as the first two pages are blocking (suggesting that Apache isn't
getting around to starting PHP during this time).


------------------------------------------------------------------------


--
Edit this bug report at [url]http://bugs.php.net/?id=40594&edit=1[/url]

[karldray at interchange dot ubc dot ca]

ID: 40594
User updated by: karldray at interchange dot ubc dot ca
Reported By: karldray at interchange dot ubc dot ca
-Status: Open
+Status: Closed
Bug Type: Sockets related
Operating System: Windows XP
PHP Version: 5.2.1
New Comment:

I'm resubmitting this bug as a performance problem. (See previous
comment.)


Previous Comments:
------------------------------------------------------------------------

[2007-02-22 21:53:47] karldray at interchange dot ubc dot ca

This turns out not to be specific to sockets or even to blocking
functions! I just realized that if I replace udp_recv.php with a
one-line script like
sleep(10);
or something like
for($i=0;$i<100000000;$i++);
then the same problem occurs: while two of them are running, apache
won't handle any new requests.

------------------------------------------------------------------------

[2007-02-22 16:39:34] karldray at interchange dot ubc dot ca

Description:
------------
I have a PHP page that opens a UDP socket and listens for data
(blocking on socket_recvfrom). When the socket recieves a packet, the
script echoes a message and finishes. This works fine, but when two
instances of this page are running (both blocking on socket_recvfrom),
Apache (2.2.4) stops responding to any new requests (even for non-php
pages) until one of them gets unblocked. The same problem occurs with
other blocking socket functions (such as socket_accept and socket_read
with TCP sockets).

Reproduction instructions:
1. open a browser window to udp_recv.php?port=11111. it sits there
"loading" since PHP is waiting for socket data.
2. open another browser window to udp_recv.php?port=22222.
3 (the problem). open another browser window and point it to index.html
or any other url on the server. it just sits there "loading".
4. in a command prompt, type "perl udp_send.pl 11111" to send 'hello'
to the first php script's udp socket, causing it to finish. Suddenly,
the third request completes.

Reproduce code:
---------------
udp_recv.php:

<?php
$listener = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_bind($listener, gethostbyname('localhost'), $_GET['port']) or
exit('error on bind');
$len = socket_recvfrom($listener, $data, 2048, 0, $host, $port);
echo "$len bytes recieved from $host:$port: $data\n";
?>

udp_send.pl:

use strict; use Socket;
socket(SOCKET, PF_INET, SOCK_DGRAM, getprotobyname('udp')) or die
"socket: $!";
send(SOCKET, 'hello', 0, sockaddr_in(shift, inet_aton('localhost'))) or
die "send: $!";


Expected result:
----------------
I expect Apache to continue to accept and handle new web page requests
while the two PHP pages are blocking on socket functions.

Actual result:
--------------
Once there are two PHP pages blocking on socket functions, all
subsequent requests (even for non-php URIs) appear as "loading" in the
browser until one of the PHP scripts unblocks.

Note: If the third request is for a PHP page containing an error_log()
at the very beginning, then the logfile output is not generated as long
as the first two pages are blocking (suggesting that Apache isn't
getting around to starting PHP during this time).


------------------------------------------------------------------------


--
Edit this bug report at [url]http://bugs.php.net/?id=40594&edit=1[/url]

[tony2001@php.net]

ID: 40594
Updated by: [email]tony2001@php.net[/email]
Reported By: karldray at interchange dot ubc dot ca
-Status: Closed
+Status: Bogus
Bug Type: Sockets related
Operating System: Windows XP
PHP Version: 5.2.1


Previous Comments:
------------------------------------------------------------------------

[2007-02-22 21:57:02] karldray at interchange dot ubc dot ca

I'm resubmitting this bug as a performance problem. (See previous
comment.)

------------------------------------------------------------------------

[2007-02-22 21:53:47] karldray at interchange dot ubc dot ca

This turns out not to be specific to sockets or even to blocking
functions! I just realized that if I replace udp_recv.php with a
one-line script like
sleep(10);
or something like
for($i=0;$i<100000000;$i++);
then the same problem occurs: while two of them are running, apache
won't handle any new requests.

------------------------------------------------------------------------

[2007-02-22 16:39:34] karldray at interchange dot ubc dot ca

Description:
------------
I have a PHP page that opens a UDP socket and listens for data
(blocking on socket_recvfrom). When the socket recieves a packet, the
script echoes a message and finishes. This works fine, but when two
instances of this page are running (both blocking on socket_recvfrom),
Apache (2.2.4) stops responding to any new requests (even for non-php
pages) until one of them gets unblocked. The same problem occurs with
other blocking socket functions (such as socket_accept and socket_read
with TCP sockets).

Reproduction instructions:
1. open a browser window to udp_recv.php?port=11111. it sits there
"loading" since PHP is waiting for socket data.
2. open another browser window to udp_recv.php?port=22222.
3 (the problem). open another browser window and point it to index.html
or any other url on the server. it just sits there "loading".
4. in a command prompt, type "perl udp_send.pl 11111" to send 'hello'
to the first php script's udp socket, causing it to finish. Suddenly,
the third request completes.

Reproduce code:
---------------
udp_recv.php:

<?php
$listener = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_bind($listener, gethostbyname('localhost'), $_GET['port']) or
exit('error on bind');
$len = socket_recvfrom($listener, $data, 2048, 0, $host, $port);
echo "$len bytes recieved from $host:$port: $data\n";
?>

udp_send.pl:

use strict; use Socket;
socket(SOCKET, PF_INET, SOCK_DGRAM, getprotobyname('udp')) or die
"socket: $!";
send(SOCKET, 'hello', 0, sockaddr_in(shift, inet_aton('localhost'))) or
die "send: $!";


Expected result:
----------------
I expect Apache to continue to accept and handle new web page requests
while the two PHP pages are blocking on socket functions.

Actual result:
--------------
Once there are two PHP pages blocking on socket functions, all
subsequent requests (even for non-php URIs) appear as "loading" in the
browser until one of the PHP scripts unblocks.

Note: If the third request is for a PHP page containing an error_log()
at the very beginning, then the logfile output is not generated as long
as the first two pages are blocking (suggesting that Apache isn't
getting around to starting PHP during this time).


------------------------------------------------------------------------


--
Edit this bug report at [url]http://bugs.php.net/?id=40594&edit=1[/url]