.. index:: advanced installation topics, laptop, virtual machine

.. _advanced_installation:

Advanced Installation Topics
############################

The :ref:`basic installation guide <installation>` should be a good
start for most users installing LAVA. For more advanced users, here is
much more information and recommendations for administrators.

Requirements to Consider Before Installing LAVA
***********************************************

.. _laptop_requirements:

Laptops
=======

Be careful with laptop installations, particularly if you are using
health checks. It is all too easy for a health check to take the
device offline just because the laptop was suspended or without an
internet connection at the relevant moment.

Laptops also have limitations on device availability but are routinely
used as development platforms and can support QEMU devices without
problems.

.. _virtual_machine_requirements:

Virtual Machines
================

LAVA installations inside a virtual machine (or container) have
particular constraints. A QEMU device or container may suffer from
being executed within the constraints of the existing virtualisation
and other devices may need USB device nodes to be passed through to
the VM. Depending on the VM, it is also possible that storage space
for the logs may become an issue.

.. _workload_requirements:

Workload
========

Consider the expected load on the master and each of the workers:

* The workload on the **master** primarily depends on:

  #. the visibility of the instance,
  #. the number of users,
  #. the average number of jobs in the queue and
  #. the total number of devices attached across all the workers connected to
     this master.

* The workload on the **worker** involves a range of tasks, scaling
  with the number of devices attached to the worker:

  #. doing a lot of synchronous I/O,
  #. decompression of large files
  #. serving large files over TFTP or HTTP and
  #. git clone operations.

An ARMv7 device can serve as a small master or worker, but SATA
support is **strongly** recommended along with at least 2GB of RAM.

Localhost
=========

LAVA expects to be the primary virtual host configured on the
master. This has improved with V2 but unless your instance is V2-only,
you may experience problems or require additional configuration to use
LAVA as a virtual host.

.. index:: infrastructure requirements

.. _infrastructure_requirements:

Other infrastructure
====================

LAVA will need other services to be available, either using separate tools on
the same machines or as separate hardware. This list is not exhaustive.

.. index:: power control infrastructure, automated power control

.. _power_control_infrastructure:

Remote power control
--------------------

Automated power control using a :abbr:`PDU (Power Distribution Unit)`
is one of the most common issues to be solved when setting up a new
LAVA lab. Hardware can be difficult to obtain and configuring the
remote power control can require custom scripting. There is no single
perfect device for all use cases, and a wide variety of possible
solutions may exist to cover your needs. Take the time to research the
issues and ask on the :ref:`lava_users` mailing list if you need
guidance.

.. index:: serial console support, serial console server

.. _serial_console_support:

Serial console support
----------------------

Once more than a handful of devices are attached to a worker it will
often become necessary to have a separate unit to handle the serial
connectivity, turning serial ports into TCP ports. Bespoke serial
console servers can be expensive; alternatives include ARMv7 boards
with ``ser2net`` installed but the USB and ethernet support needs to
be reliable for this to work well.

.. _network_switch_infrastructure:

Network switches
----------------

Simple unmanaged switches will work for small LAVA labs but managed switches
are essential to use :ref:`vland_in_lava` and will also be important for medium
to large LAVA labs.

.. _power_supply_ups:

Power supply
------------

Use of a :abbr:`UPS (Uninterruptible Power Supply)` will allow the entire
lab to cope with power interruptions. Depending on the budget, this
could be a small UPS capable of supporting the master and the worker
for 10 minutes, or it could be a combination of larger UPS units and a
generator.

.. _fileserver_infrastructure:

Fileserver
----------

The master is **not** the correct place to be building or storing
build artefacts. In a busy lab, the extra load may cause issues when
workers download large files at job startup. Development builds and
creation of files to support the LAVA test should happen on a suitably
powerful machine to meet the performance expectations of the CI loop
and the developers.

Shelving and racks
------------------

While it may be tempting to set up a lab on a desk or test bench, this
can very quickly degenerate into a tangled mess as more devices are
added. On top of the test devices, switches and other infrastructure,
there will be a lot of power cables, network cables and serial
cables. For even a small lab of a handful of devices, a set of shelves
or a wall-mounted rack is going to make things a lot easier to manage.

.. _more_installation_types:

Recommended Installation Types
******************************

Single instance
===============

The :ref:`basic guide <installation>` shows how to install
``lava-server`` and ``lava-dispatcher`` on a single machine. This kind
of simple instance can be very useful for local development, testing
inside virtual machines and small scale testing.

However, the most obvious limitation of the single-instance
installation is on the number of devices which can be supported. This
normally is controlled by the number of test devices that may be
connected directly to the machine. The solution here is easy: as your
lab grows, keep the original machine as the master. Add one or more
new machines as workers, and move test devices over to those new
workers.

Master with one or more remote workers
======================================

Any single instance of LAVA V2 can be extended to work with one or
more workers which only need the ``lava-dispatcher`` package
installed.

.. seealso:: :ref:`Installing a worker <installing_pipeline_worker>`

Authentication and encryption
-----------------------------

When the worker is on the same trusted network as the master,
administrators may safely choose to connect workers to the master
without authentication. In all other cases, the ZMQ socket used for
passing control messages to the worker and the socket used to pass
logs back to the master should use authentication and :ref:`encryption
<zmq_curve>`.

Authentication needs to be configured on the master first, then
workers can be :ref:`prepared <installing_pipeline_worker>` and
configured to match.

Other installation notes
************************

.. _automated_installation:

Automated installation
======================

Using debconf pre-seeding with Debian packages
----------------------------------------------

Debconf is the standard method on Debian systems for controlling and
storing high-level configuration for packages. Debian packages may ask
questions during installation to set up this configuration. Debconf
may also be automated, using a text file which contains the answers to
those debconf questions - just keep the file up to date if the
questions change. For example, to preseed a worker install:

.. code-block:: shell

 $ cat preseed.txt
 lava-server   lava-worker/db-port string 5432
 lava-server   lava-worker/db-user string lava-server
 lava-server   lava-server/master boolean false
 lava-server   lava-worker/master-instance-name string default
 lava-server   lava-worker/db-server string snagglepuss.codehelp
 lava-server   lava-worker/db-pass string werewolves
 lava-server   lava-worker/db-name string lava-server

To insert the preseed information into the debconf database:

.. code-block:: shell

 $ sudo debconf-set-selections < preseed.txt

or to show the existing debconf information for a package:

.. code-block:: shell

 $ sudo debconf-show lava-server
 * lava-worker/master-instance-name: default
 * lava-server/master: false
 * lava-worker/db-pass: werewolves
 * lava-worker/db-port: 5432
 * lava-worker/db-name: lava-server
 * lava-worker/db-server: snagglepuss.codehelp
 * lava-worker/db-user: lava-server

The strings available for seeding are in the Debian packaging for the
relevant package, in the ``debian/<PACKAGE>.templates`` file.

* http://www.debian-administration.org/articles/394
* http://www.fifi.org/doc/debconf-doc/tutorial.html

.. _branding:

LAVA server branding support
============================

The icon, link, alt text, bug URL and source code URL of the LAVA link on each
page can be changed in the settings ``/etc/lava-server/settings.conf`` (JSON
syntax)::

   "BRANDING_URL": "http://www.example.org",
   "BRANDING_ALT": "Example site",
   "BRANDING_ICON": "https://www.example.org/logo/logo.png",
   "BRANDING_HEIGHT": 26,
   "BRANDING_WIDTH": 32,
   "BRANDING_BUG_URL": "http://bugs.example.org/lava",
   "BRANDING_SOURCE_URL": "https://github.com/example/lava-server",

Admins can include a sentence describing the purpose of the instance to give more
detail than is available via the instance name. This will be added in a paragraph
on the home page under "About the {{instance_name}} LAVA instance"::

   "BRANDING_MESSAGE": "Example site for local testing",

If the icon is available under the django static files location, this location
can be specified instead of a URL::

   "BRANDING_ICON": "path/to/image.png",

There are limits to the size of the image, approximately 32x32 pixels, to avoid
overlap.

The ``favicon`` is configurable via the Apache configuration::

 Alias /favicon.ico /usr/share/lava-server/static/lava-server/images/logo.png

.. index:: security upgrades, unattended upgrades

.. _unattended_upgrades:

Unattended upgrades
===================

Debian provides a package called ``unattended-upgrades`` which can be
installed to automatically install security (and other) updates on
Debian systems. This service is recommended for LAVA instances, but is
not part of LAVA itself.

If you plan to use ``unattended-upgrades``, it is a good idea to set
up monitoring on your systems, for example by also installing
``apt-listchanges`` and configuring email for administrator
use. Ensure that the master and all workers are similarly configured,
to avoid potential problems with skew in package versions.

.. seealso:: https://wiki.debian.org/UnattendedUpgrades

Example changes
---------------

``/etc/apt/apt.conf.d/50unattended-upgrades``

The default installation of ``unattended-upgrades`` enables automatic
upgrades for all security updates::

   Unattended-Upgrade::Origins-Pattern {

        "origin=Debian,codename=jessie,label=Debian-Security";
   };


Optionally add automatic updates from the :ref:`lava_repositories` if those are
in use::

   Unattended-Upgrade::Origins-Pattern {

        "origin=Debian,codename=jessie,label=Debian-Security";
        "origin=Linaro,label=Lava";
   };

Other repositories can be added to the upgrade by checking the output of
``apt-cache policy``, e.g.::

 release v=8.1,o=Linaro,a=unstable,n=sid,l=Lava,c=main

Relates to an origin (``o``) of ``Linaro`` and a label (``l``) of ``Lava``.

When configuring unattended upgrades for the master or any worker which still
supports LAVA V1, PostgreSQL will need to be added to the
``Package-Blacklist``. Although services like PostgreSQL do get security
updates and these updates **are** important to apply, ``unattended-upgrades``
does not currently restart other services which are dependent on the service
being upgraded. Admins still need to watch for security updates to PostgreSQL
and apply the update manually, restarting services like ``lavapdu-runner``,
``lava-master``, ``lava-server`` and ``vland`` afterwards::

   Unattended-Upgrade::Package-Blacklist {
        "postgresql-9.4";
   };

Email notifications also need to be configured.

::

   Unattended-Upgrade::Mail "lava-admins@example.com";

   Unattended-Upgrade::MailOnlyOnError "true";

With these changes to ``/etc/apt/apt.conf.d/50unattended-upgrades``, the rest
of the setup is as described on the Debian wiki.

https://wiki.debian.org/UnattendedUpgrades#automatic_call_via_.2Fetc.2Fapt.2Fapt.conf.d.2F20auto-upgrades

.. index:: event notifications - configuration

.. _configuring_event_notifications:

Configuring event notifications
===============================

Event notifications **must** be configured before being enabled.

* All changes need to be configured in ``/etc/lava-server/settings.conf`` (JSON
  syntax).

* Ensure that the ``EVENT_TOPIC`` is **changed** to a string which the
  receivers of the events can use for filtering.

  * Instances in the Cambridge lab use a convention which is similar
    to that used by DBus or Java, simply reversing the domain name
    for the instance (e.g. ``org.linaro.validation``)

* Ensure that the ``EVENT_SOCKET`` is visible to the receivers - change the
  default port of ``5500`` if required.

* Enable event notifications by setting ``EVENT_NOTIFICATION`` to ``true``

When changing the configuration, you should restart the corresponding services:

.. code-block:: shell

  $ sudo service lava-publisher restart
  $ sudo service lava-master restart
  $ sudo service lava-server restart
  $ sudo service lava-server-gunicorn restart

The default values for the event notification settings are:

.. code-block:: python

 "EVENT_TOPIC": "org.linaro.validation",
 "INTERNAL_EVENT_SOCKET": "ipc:///tmp/lava.events",
 "EVENT_SOCKET": "tcp://*:5500",
 "EVENT_NOTIFICATION": false,
 "EVENT_ADDITIONAL_SOCKETS": []

The ``INTERNAL_EVENT_SOCKET`` does not usually need to be changed.

Services which will receive these events **must** be able to connect to the
``EVENT_SOCKET``. Depending on your local configuration, this may involve
opening the specified port on a firewall.

Events and network reliability
------------------------------

With the default configuration, LAVA will publish events to the
``EVENT_SOCKET`` only, using a `zmq PUB socket
<http://api.zeromq.org/4-2:zmq-socket#toc7>`__. This type of socket is
efficient for publishing messages to a large audience. However, in
case of a network breakage, the connection may be lost and events may
be missed.

For more reliable event publication on an unreliable network (like the
Internet) with a small set of known listeners, you can also use
``EVENT_ADDITIONAL_SOCKETS``. The publisher will connect to each of
the endpoints in this list using a `zmq PUSH socket
<http://api.zeromq.org/4-2:zmq-socket#toc12>`__. These sockets are
configured to keep a large queue of messages for each of the
endpoints, and will retry to deliver those messages as necessary. No
messages will be lost until the queue overflows.

.. seealso:: :ref:`publishing_events`

LAVA server performances
************************

If the load on the master becomes an issue, there may be some optimisations
which can help.

The default settings should work out of the box. This might not be the case for
some optimisations that should be tested carefully.

Caching
=======

The different assets (CSS, js, images, etc.) are already handled directly by
apache but without any caching.

To add browser caching, update the apache2 configuration to add Expires header
for every static assets.

.. code-block:: apache

  <location /static>
    ExpiresActive On
    ExpiresDefault "access plus 1 month"
  </location>

.. note:: For the complete documentation see the `apache documentation
   <https://httpd.apache.org/docs/2.4/mod/mod_expires.html>`__

Template caching
================

Django does also provide a way to store in memory the compiled version of the
templates using the `cached loader
<https://docs.djangoproject.com/en/1.10/ref/templates/api/#django.template.loaders.cached.Loader>`__.

To enable the cached loader, in */etc/lava-server/settings.conf* add:

.. code-block:: none

  "USE_TEMPLATE_CACHE": true

You should then restart *lava-server-gunicorn*.

.. code-block:: shell

  $ sudo service lava-server-gunicorn restart
