53c70cf219
This patch adds notes to handle the differences between Debian and Ubuntu. backport: havana Change-Id: I0fea68e65c3c3c4d0c2538a57f3ad4e9bad11cef
227 lines
11 KiB
XML
227 lines
11 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<section xml:id="dashboard-sessions"
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xmlns="http://docbook.org/ns/docbook"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0">
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<title>Set up session storage for the dashboard</title>
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<para>The dashboard uses <link
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xlink:href="https://docs.djangoproject.com/en/dev/topics/http/sessions/"
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>Django sessions framework</link> to handle user session
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data. However, you can use any available session back end. You
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customize the session back end through the
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<literal>SESSION_ENGINE</literal> setting in your <filename>local_settings</filename> file
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(on Fedora/RHEL/CentOS: <filename>
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/etc/openstack-dashboard/local_settings</filename>, on Ubuntu and Debian:
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<filename>/etc/openstack-dashboard/local_settings.py</filename> and on openSUSE: <filename
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>/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.py</filename>).
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</para>
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<para>The following sections describe the pros and cons of each
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option as it pertains to deploying the dashboard.</para>
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<section xml:id="dashboard-session-local">
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<title>Local memory cache</title>
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<para>Local memory storage is the quickest and easiest session
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back end to set up, as it has no external dependencies
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whatsoever. It has the following significant
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drawbacks:</para>
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<itemizedlist>
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<listitem>
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<para>No shared storage across processes or
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workers.</para>
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</listitem>
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<listitem>
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<para>No persistence after a process
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terminates.</para>
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</listitem>
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</itemizedlist>
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<para>The local memory back end is enabled as the default for
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Horizon solely because it has no dependencies. It is not
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recommended for production use, or even for serious
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development work. Enabled by:</para>
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<programlisting language="python"><?db-font-size 75%?>SESSION_ENGINE = 'django.contrib.sessions.backends.cache'
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CACHES = {
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'BACKEND': 'django.core.cache.backends.locmem.LocMemCache'
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}</programlisting>
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</section>
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<section xml:id="dashboard-session-key-value-store">
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<?dbhtml stop-chunking?>
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<title>Key-value stores</title>
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<para>You can use applications such as Memcached or Redis for external
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caching. These applications offer persistence and shared storage
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and are useful for small-scale deployments and/or development.
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</para>
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<section xml:id="dashboard-session-memcached">
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<title>Memcached</title>
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<para>Memcached is an high-performance and distributed memory object caching system
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providing in-memory key-value store for small chunks of arbitrary data.</para>
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<para>Requirements:</para>
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<itemizedlist>
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<listitem>
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<para>Memcached service running and accessible.</para>
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</listitem>
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<listitem>
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<para>Python module <literal>python-memcached</literal> installed.</para>
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</listitem>
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</itemizedlist>
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<para>Enabled by:</para>
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<programlisting language="python"><?db-font-size 75%?>SESSION_ENGINE = 'django.contrib.sessions.backends.cache'
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CACHES = {
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'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache'
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'LOCATION': 'my_memcached_host:11211',
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}</programlisting>
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</section>
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<section xml:id="dashboard-session-redis">
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<title>Redis</title>
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<para>Redis is an open source, BSD licensed, advanced key-value store. It is often referred
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to as a data structure server.</para>
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<para>Requirements:</para>
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<itemizedlist>
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<listitem>
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<para>Redis service running and accessible.</para>
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</listitem>
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<listitem>
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<para>Python modules <literal>redis</literal> and <literal>django-redis</literal> installed.</para>
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</listitem>
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</itemizedlist>
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<para>Enabled by:</para>
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<programlisting language="python"><?db-font-size 75%?>SESSION_ENGINE = 'django.contrib.sessions.backends.cache'
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CACHES = {
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"default": {
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"BACKEND": "redis_cache.cache.RedisCache",
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"LOCATION": "127.0.0.1:6379:1",
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"OPTIONS": {
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"CLIENT_CLASS": "redis_cache.client.DefaultClient",
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}
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}
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}</programlisting>
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</section>
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</section>
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<section xml:id="dashboard-session-database">
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<title>Database</title>
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<para>Database-backed sessions are scalable, persistent, and
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can be made high-concurrency and highly-available.</para>
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<para>However, database-backed sessions are one of the slower
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session storages and incur a high overhead under heavy
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usage. Proper configuration of your database deployment
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can also be a substantial undertaking and is far beyond
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the scope of this documentation.</para>
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<procedure>
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<title>To initialize and configure the database:</title>
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<step>
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<para>Start the mysql command line client:</para>
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<screen><prompt>$</prompt> <userinput>mysql -u root -p</userinput></screen>
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</step>
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<step>
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<para>Enter the MySQL root user's password when
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prompted.</para>
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</step>
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<step>
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<para>To configure the MySQL database, create the dash
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database:</para>
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<para><screen><prompt>mysql></prompt> <userinput>CREATE DATABASE dash;</userinput></screen></para>
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</step>
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<step>
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<para>Create a MySQL user for the newly-created dash
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database that has full control of the
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database:</para>
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<para><screen><prompt>mysql></prompt> <userinput>GRANT ALL ON dash.* TO 'dash'@'%' IDENTIFIED BY 'yourpassword';</userinput></screen></para>
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</step>
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<step>
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<para>Enter quit at the <literal>mysql></literal>
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prompt to exit MySQL.</para>
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</step>
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<step>
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<para>In the <filename>local_settings</filename> file
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(on Fedora/RHEL/CentOS: <filename>
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/etc/openstack-dashboard/local_settings</filename>, on Ubuntu:
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<filename>local_settings.py</filename> and on openSUSE: <filename
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>/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.py</filename>),
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change these options:</para>
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<programlisting language="python"><?db-font-size 75%?>SESSION_ENGINE = 'django.core.cache.backends.db.DatabaseCache'
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DATABASES = {
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'default': {
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# Database configuration here
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'ENGINE': 'django.db.backends.mysql',
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'NAME': 'dash',
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'USER': 'dash',
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'PASSWORD': 'yourpassword',
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'HOST': 'localhost',
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'default-character-set': 'utf8'
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}
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}</programlisting>
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</step>
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<step>
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<para>After configuring the <filename>local_settings</filename>
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as shown, you can run the <command>manage.py
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syncdb</command> command to populate this
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newly-created database.</para>
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<screen><prompt>$</prompt> /usr/share/openstack-dashboard/manage.py syncdb </screen>
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<para>As a result, the following output is
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returned:</para>
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<screen><computeroutput>Installing custom SQL ...
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Installing indexes ...
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DEBUG:django.db.backends:(0.008) CREATE INDEX `django_session_c25c2c28` ON `django_session` (`expire_date`);; args=()
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No fixtures found.</computeroutput></screen>
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</step>
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<step>
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<para>On Ubuntu: If you want to avoid a warning when you restart
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apache2, create a blackhole directory in the
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dashboard directory, as follows:</para>
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<screen><prompt>#</prompt> <userinput>sudo mkdir -p /var/lib/dash/.blackhole</userinput></screen>
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</step>
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<step>
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<para>Restart Apache to pick up the default site and
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symbolic link settings:</para>
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<para>On Ubuntu:
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<screen><prompt>#</prompt> <userinput>/etc/init.d/apache2 restart</userinput></screen>
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</para>
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<para>On Fedora/RHEL/CentOS:
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<screen><prompt>#</prompt> <userinput>service httpd restart</userinput></screen>
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<screen><prompt>#</prompt> <userinput>service apache2 restart</userinput></screen>
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</para>
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<para>On openSUSE:
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<screen><prompt>#</prompt> <userinput>systemctl restart apache2.service</userinput></screen>
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</para>
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</step>
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<step>
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<para>On Ubuntu, restart the <systemitem class="service">nova-api</systemitem> service to ensure that the
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API server can connect to the dashboard without
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error:</para>
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<screen><prompt>#</prompt> <userinput>sudo restart nova-api</userinput></screen>
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</step>
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</procedure>
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</section>
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<section xml:id="dashboard-session-cached-database">
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<title>Cached database</title>
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<para>To mitigate the performance issues of database queries,
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you can use the Django cached_db session back end, which
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utilizes both your database and caching infrastructure to
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perform write-through caching and efficient retrieval.</para>
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<para>Enable this hybrid setting by configuring both your
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database and cache, as discussed previously. Then, set the
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following value:</para>
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<programlisting language="python"><?db-font-size 75%?>SESSION_ENGINE = "django.contrib.sessions.backends.cached_db"</programlisting>
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</section>
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<section xml:id="dashboard-session-cookies">
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<title>Cookies</title>
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<para>If you use Django 1.4 or later, the signed_cookies
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back end avoids server load and scaling problems.</para>
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<para>This back end stores session data in a cookie, which is
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stored by the user’s browser. The back end uses a
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cryptographic signing technique to ensure session data is
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not tampered with during transport. This is not the same
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as encryption; session data is still readable by an
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attacker.</para>
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<para>The pros of this engine are that it requires no
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additional dependencies or infrastructure overhead, and it
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scales indefinitely as long as the quantity of session
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data being stored fits into a normal cookie.</para>
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<para>The biggest downside is that it places session data into
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storage on the user’s machine and transports it over the
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wire. It also limits the quantity of session data that can
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be stored.</para>
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<para>See the Django <link
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xlink:href="https://docs.djangoproject.com/en/dev/topics/http/sessions/#using-cookie-based-sessions"
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>cookie-based sessions</link> documentation.</para>
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</section>
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</section>
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