[Koha-bugs] [Bug 11974] Enable unix socket connections for database connections.

[bugzilla-daemon at bugs.koha-community.org]

http://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=11974

Olli-Antti Kivilahti <olli-antti.kivilahti at jns.fi> changed:

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  Attachment #26486|0                           |1
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--- Comment #15 from Olli-Antti Kivilahti <olli-antti.kivilahti at jns.fi> ---
Created attachment 26505
  -->
http://bugs.koha-community.org/bugzilla3/attachment.cgi?id=26505&action=edit
Bug 11974 - Enable unix socket connections for database connections.

-----------------
- BUSINESS CASE -
-----------------
Currently Koha doesn't support using a non-default unix socket for database
connections.
Using unix sockets is generally ~20-30% faster compared to using TCP packets.
Because
Koha abuses the database a lot, this will make a difference.

Using a non-default unix socket is useful if you want to run multiple databases
(eg. mysql and mariadb) in the same OS (eg. for testing purposes).
Also if one needs to move the unix socket, for example to share it between LXC
containers
using a shared partition, this feature might be handy.

Using unix sockets for connections are faster than TCP because there is no need
for TCP
and IP layer packet generation. Instead applications can communicate directly
without
extra overhead.
The benefit is marginal for a single query, around 0.5ms, but escalates
linearly when
hundreds of queries are performed.

------------
- SOLUTION -
------------
Mysql uses unix sockets for localhost connections only, but DBI::Mysql cannot
automatically
find the non-default socket path, thus it needs to be explicitly given.

This patch modifies the C4::Context->dbh() routine to check for the presence of
mysql_socket in koha-conf.xml and prioritize the socket connection.
If making the socket connection fails, dbh() defaults to the TCP-connection if
available.

This patch works on MariaDB and Mysql, hence the configuration variable name
mysql_socket.

-------------
- TEST PLAN -
-------------
DEFAULT:
1.  edit koha-conf.xml
1.1.  uncomment row <mysql_socket>... and put your socket path here,
      by default /var/run/mysqld/mysqld.sock  .
      or create the xml-entry
<mysql_socket>/var/run/mysqld/mysqld.sock</mysql_socket>
2.  load any koha's web-page. Shouldn't get any errors.

SOCKET ONLY:
replicate DEFAULT and do the following instructions:
3.  From koha-conf.xml, remove hostname or set to bad name.
4.  load any koha's web page.
5.  Mysql/MariaDB connection works faster than ever!

BAD SOCKET:
1.  but a bad path as your mysql_socket, eg /var/run/mysqld/mysqld.sockBADBAD
2.  load any koha's web-page. see your koha-error_log or koha-opac-error_log
for the error.
    You can still use Koha normally, but it is recommended to fix bad socket
ASAP.

TOTAL DESTRUCTION:
replicate BAD SOCKET and do the following instructions:
3.  from koha-conf.xml remove hostname or change to a bad one.
4.  load any koha's web page. Enjoy the "Software error".

Thank you for testing!

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