Tag: php

Persistent connections for PHP sessions stored using Memecached

If you have a highly loaded PHP application server you probably came to conclusion to use memcached to store the PHP sessions, because files are too slow and generate many IOs. And when the session are enabled to be stored in memcached server the server could be overloaded with so many connections to the memcached instance(s) that the server could delay the creation of new connections to the memcached server and the server is in trouble even more than before with the file stored sessions.
The solution is to use persistent connections to the memcached server, so when a connection to the memcached is needed it will check to reuse an existing idle connection stored in a pool of connections so no new connection is created each time PHP needs something from the cache like the sessions. In fact PHP accesses sessions from the cache at least once for every request to the server and it could generate a pretty big number of opened connections.

On top of that there are two PHP modules, which offer objects or functions to use memcached server cache in your PHP code. The old module is called “memcache” (link) and the new one is “memcached” (link) – just to note these are the names of the PHP modules not to be mistaken by the server caching system “memcached”.

To configure the php-fpm or mod_php to store sessions in memcached caching server:

  1. use PHP “memcached”, this is the new and better supported module for using a memcached cache server. It supports the newer versions of PHP like 7+.
  2. use the following configuration added to your php.ini or the module ini file included in your php.ini (it really depends on your configuration, but if you are not sure put phpinfo() function in a PHP file and load through your web server – you’ll see the physical location of your php.ini file);
session.save_path = "PERSISTENT=1 localhost:11212"

Replace localhost with the server IP or leave it if the memcached server is on the localhost. This single configuration could decrease the usage of opened sockets from several tens of thousands (literally 30 000 – 100 000 and above) to couple of hundreds, which could have a great impact on system performance! (You’ll see it like a system usage time in your server graphs…)

*Worth mentioning the PHP configuration (php.ini file) must be edited to use memcached server for storing sessions:

session.save_handler = memcached

Access Violation error, when compiling packages in Gentoo

Sometimes if you try to emerge a package in Gentoo you could receive error in the configure phase of the compilation process. The example below is with the emerging the PHP – dev-lang/php-5.6.33:5.6::gentoo, but could happen with many other packages, which are rather old and probably not maintained or the sandbox or even the portage packages are old.
So here is the error and the compilation stops:

srv ~ # emerge -av --nodeps "<php-7"
...
checking for mmap() using MAP_ANON shared memory support... yes
checking for mmap() using /dev/zero shared memory support... yes
checking for mmap() using shm_open() shared memory support...  * ACCESS DENIED:  open_wr:      /run/test.shm.8811LBKone
no
checking for mmap() using regular file shared memory support... yes
...
checking for mmap() using MAP_ANON shared memory support... yes
checking for mmap() using /dev/zero shared memory support... yes
checking for mmap() using shm_open() shared memory support...  * ACCESS DENIED:  open_wr:      /run/test.shm.180309hAMbj
no
checking for mmap() using regular file shared memory support... yes
....
Thank you for using PHP.
config.status: creating php5.spec
config.status: creating main/build-defs.h
config.status: creating scripts/phpize
config.status: creating scripts/man1/phpize.1
config.status: creating scripts/php-config
config.status: creating scripts/man1/php-config.1
config.status: creating ext/phar/phar.1
config.status: creating ext/phar/phar.phar.1
config.status: creating main/php_config.h
config.status: executing libtool commands
config.status: executing default commands
>>> Source configured.
 * --------------------------- ACCESS VIOLATION SUMMARY ---------------------------
 * LOG FILE: "/var/log/sandbox/sandbox-13466.log"
 * 
VERSION 1.0
FORMAT: F - Function called
FORMAT: S - Access Status
FORMAT: P - Path as passed to function
FORMAT: A - Absolute Path (not canonical)
FORMAT: R - Canonical Path
FORMAT: C - Command Line

F: open_wr
S: deny
P: /run/test.shm.21532Xx6ViE
A: /run/test.shm.21532Xx6ViE
R: /run/test.shm.21532Xx6ViE
C: ./conftest 

F: open_wr
S: deny
P: /run/test.shm.31817hurGxH
A: /run/test.shm.31817hurGxH
R: /run/test.shm.31817hurGxH
C: ./conftest 

F: open_wr
S: deny
P: /run/test.shm.8811LBKone
A: /run/test.shm.8811LBKone
R: /run/test.shm.8811LBKone
C: ./conftest 

F: open_wr
S: deny
P: /run/test.shm.180309hAMbj
A: /run/test.shm.180309hAMbj
R: /run/test.shm.180309hAMbj
C: ./conftest 
 * --------------------------------------------------------------------------------

>>> Failed to emerge dev-lang/php-5.6.33, Log file:

>>>  '/var/tmp/portage/dev-lang/php-5.6.33/temp/build.log'

You could try adding “-sandbox” to feature in “/etc/portage/make.conf”

FEATURES="-sandbox"

But

the sandbox feature is very important and should not be disabled by default.

And that’s why sometime when you disable it with “-sandbox” you still get access violation and you still cannot install/compile the package!
The thing is you see the error and you can fix it easily. The important part is the directory, which causes the error, in the above example with “dev-lang/php”, but could be any other Gentoo package, the problem is the writing permission for files in “/run” directory. So open the configuration file

/etc/sandbox.d/00default

and you’ll see the there is a variable called SANDBOX_WRITE, which accept paths. If you add to this variable at the end the directory “/run” or your access violated directory you’ll be able to install/compile your package with no problems, for the above problem the solution was:

SANDBOX_WRITE="/usr/tmp/conftest:/usr/lib/conftest:/usr/lib32/conftest:/usr/lib64/conftest:/usr/tmp/cf:/usr/lib/cf:/usr/lib32/cf:/usr/lib64/cf:/run"

PHP posix_kill missing in CentOS7

So you think you PHP code is running ok and your script for killing bad guys is perfect. Let’s assume you made a script to kill processes according to some criteria, put you script on your good all CentOS 7 server, but suddenly you encounter the error:

PHP Fatal error: Call to undefined function posix_kill() in ./kill-process.php on line 64
Killed process id: 21899
PHP Fatal error: Call to undefined function posix_kill() in ./kill-process.php on line 64
Killed process id: 21899
PHP Fatal error: Call to undefined function posix_kill() in ./kill-process.php on line 64

So you just missed a php plugin and there it is: “php-process”. Just install it with yum!

yum install -y php-process

And the error will disappear and the next time you want to kill some bad process you’ll sure do it!