PHP module compilation error – libtool: Version mismatch error

If you happen to get this error trying to build your own a PHP module (probably, because you need a newer version than the included one in the disto you use and because it is fairly easy):

libtool: Version mismatch error.  This is libtool 2.4.6, but the
libtool: definition of this LT_INIT comes from an older release.
libtool: You should recreate aclocal.m4 with macros from libtool 2.4.6
libtool: and run autoconf again.
make: *** [Makefile:181: geoip.lo] Error 63

Here is what you can do to recreate the configuration files for the build process:

libtoolize --force

This sequence of commands (probably without the phpize, because it is PHP specific) could save you in similar situations with similar error in other source code not related to PHP.
Keep on reading!

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

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!