=============
Server tuning
=============

Using cron to perform background jobs
-------------------------------------

See :doc:`../configuration_server/background_jobs_configuration` for a description and the
benefits.

Reducing system load
--------------------

High system load will slow down Nextcloud and might also lead to other unwanted 
side effects. To reduce load you should first identify the source of the problem. 
Tools such as htop, iotop, `netdata <https://my-netdata.io>`_ or
`glances <https://nicolargo.github.io/glances/>`_
will help to identify the process or the drive that slows down your system. First 
you should make sure that you installed/assigned enough RAM. Swap usage should be 
prevented by all means. If you run your database inside a VM, you should not 
store it inside a VM image file. Better put it on a dedicated block device to 
reduce latency due to multiple abstraction layers.

.. _caching:

Caching
-------

Caching improves performance by storing data, code, and other objects in memory. 
Memory cache configuration for the Nextcloud server must be installed and configured.
See :doc:`../configuration_server/caching_configuration`.

Using MariaDB/MySQL instead of SQLite
-------------------------------------

MySQL or MariaDB are preferred because of the `performance limitations of 
SQLite with highly concurrent applications 
<http://www.sqlite.org/whentouse.html>`_, like Nextcloud.

See the section :doc:`../configuration_database/linux_database_configuration` for how to
configure Nextcloud for MySQL or MariaDB. If your installation is already running on
SQLite then it is possible to convert to MySQL or MariaDB using the steps provided
in :doc:`../configuration_database/db_conversion`.

In smaller installations you might not want to set up a separate cache. However 
you can still tune your database. The following example is suited for a database 
smaller than 1GB. MySQL will consume up to 1GB of RAM for caching. Please make 
sure that your system has sufficient free RAM after the change, so that it does 
not start to use your swap partition, when it receives a burst of requests. In 
the given example your ``/etc/mysql/conf.d/mysql.cnf`` might contain the 
following lines. (beware that this is the block for mysqld not mysql)

.. code:: ini

  [mysqld]
  innodb_buffer_pool_size=1G
  innodb_io_capacity=4000

Using Redis-based transactional file locking
--------------------------------------------

File locking is enabled by default, using the database locking backend. This 
places a significant load on your database. See the section
:doc:`../configuration_files/files_locking_transactional` for how to
configure Nextcloud to use Redis-based Transactional File Locking.

SSL / encryption app
--------------------

SSL (HTTPS) and file encryption/decryption can be offloaded to a processor's 
AES-NI extension. This can both speed up these operations while lowering 
processing overhead. This requires a processor with the `AES-NI instruction set 
<http://wikipedia.org/wiki/AES_instruction_set>`_.

Here are some examples how to check if your CPU / environment supports the 
AES-NI extension:

* For each CPU core present: ``grep flags /proc/cpuinfo`` or as a summary for 
  all cores: ``grep -m 1 ^flags /proc/cpuinfo`` If the result contains any 
  ``aes``, the extension is present.   

* Search eg. on the Intel web if the processor used supports the extension 
  `Intel Processor Feature Filter 
  <http://ark.intel.com/MySearch.aspx?AESTech=true>`_ You may set a filter by 
  ``"AES New Instructions"`` to get a reduced result set.
   
* For versions of openssl >= 1.0.1, AES-NI does not work via an engine and 
  will not show up in the ``openssl engine`` command. It is active by default 
  on the supported hardware. You can check the openssl version via ``openssl 
  version -a``
    
* If your processor supports AES-NI but it does not show up eg via grep or 
  coreinfo, it is maybe disabled in the BIOS.
  
* If your environment runs virtualized, check the virtualization vendor for 
  support.
  
Enable HTTP2 for faster loading
-------------------------------

HTTP2 has `huge speed improvements <https://www.troyhunt.com/i-wanna-go-fast-https-massive-speed-advantage/>`_ over HTTP with multiple request. Most `browsers already support HTTP2 over SSL (HTTPS) <http://caniuse.com/#feat=http2>`_. So refer to your server manual for guides on how to use HTTP2.

Tune PHP-FPM
------------

If you are using a default installation of php-fpm you might have noticed 
excessive load times on the web interface or even sync issues. This is due 
to the fact that each simultaneous request of an element is handled by a 
separate PHP-FPM process. So even on a small installation you should allow 
more processes to run. For example on a machine with 4GB of RAM and 1GB of 
MySQL cache following values in your ``www.conf`` file should work:

.. code:: ini

  pm = dynamic
  pm.max_children = 120
  pm.start_servers = 12
  pm.min_spare_servers = 6
  pm.max_spare_servers = 18
  
Depending on your current PHP version you should find this file e.g. under ``/etc/php/7.2/fpm/pool.d/www.conf``

Enable PHP OPcache
------------------

The `OPcache <http://php.net/manual/en/intro.opcache.php>`_ improves the performance of PHP applications by caching precompiled bytecode. We recommend at least following settings:

.. code:: ini

  opcache.enable=1
  opcache.enable_cli=1
  opcache.interned_strings_buffer=8
  opcache.max_accelerated_files=10000
  opcache.memory_consumption=128
  opcache.save_comments=1
  opcache.revalidate_freq=1

For more details check out the `official documentation <http://php.net/manual/en/opcache.configuration.php>`_ or `this blog post about some recommended settings <https://www.scalingphpbook.com/blog/2014/02/14/best-zend-opcache-settings.html>`_.
