Installing Graphite for use with NAV on Debian

This is a short how-to guide for installing and configuring a simple Graphite installation, dedicated to NAV, on a Debian 9 (Stretch) or Debian 10 (Buster) server.

Warning

Do not start NAV until you have properly configured your carbon-cache’s storage schemas with NAV’s provided storage schema config, or you will have issues with blank areas in your graphs, which you will need to resolve manually after-the-fact.

Getting Graphite

A full Graphite setup consists of the Carbon backend server, which receives metrics over TCP or UDP, and a Graphite web frontend, which enables browsing and retrievial/rendering of the stored metrics. NAV will collect metrics and send to the former, while utilizing the latter to retrieve metrics and render graphs.

Assuming you will be running Graphite on the same Debian server as you are running NAV, all you need to do to install Graphite on Debian 9 is:

apt-get install python-psycopg2 graphite-carbon \
  python-whisper/stretch-backports graphite-web/stretch-backports

For Debian 10, this would instead be:

apt-get install python3-psycopg2 graphite-carbon graphite-web

Configuring Carbon

Carbon, the metric-receiving backend of Graphite, must be configured before it can be used with NAV. We will only be covering the simple case of using a single carbon-cache process. Most of this information is adapted from the Integrating Graphite with NAV section of the generic installation documentation.

Edit /etc/carbon/carbon.conf to ensure these options are set in the [cache] section:

MAX_CREATES_PER_MINUTE = inf
ENABLE_UDP_LISTENER = True

The first line ensures that Carbon will not delay creating Whisper backend files for the metrics NAV sends it. The default setting is a maximum of 50 creates per minute (the setting exists to limit I/O strain on huge setups), which means that when bootstrapping a NAV installation, hours to days can pass before all its metrics are being actually stored in Graphite.

The second line ensures that Carbon accepts metrics on a UDP socket, which is required by NAV.

Carbon also needs to know the resolution at which to store your time-series data, for how long to store it, and how to roll up data from high resolution data archives to lower resolution archives. These are the storage schemas and aggregation methods. NAV provides its own config examples for this; on a Graphite backend dedicated to NAV, you can simply symlink these config files from NAV:

cd /etc/carbon/
mv storage-schemas.conf storage-schemas.conf.bak
mv storage-aggregation.conf storage-aggregation.conf.bak
ln -s /etc/nav/graphite/*.conf /etc/carbon/

Finally, restart the carbon-cache daemon:

systemctl restart carbon-cache

Configuring the Graphite web interface

To enable the web interface, you need to do two things:

  • Configure and create the database it will use for storing graph definitions.
  • Configure Apache to serve the web interface.

Creating the graphite database

Graphite will by default use a SQLite database, but this is not recommended in a production setting, as it will cause issues with multiple simultaneous users. You already have a PostgreSQL installation because of NAV, so we recommend using this.

Make a graphite PostgreSQL user and give it a password (make note of the password), then create a database owned by that user:

sudo -u postgres createuser --pwprompt --no-createrole --no-superuser --no-createdb --login graphite
sudo -u postgres createdb --owner=graphite graphite

The Graphite web app’s configuration file is located in /etc/graphite/local_settings.py. There are mainly three settings you will need to adjust: SECRET_KEY, TIME_ZONE and DATABASES. The SECRET_KEY is used for cryptographic purposes when working with cookies and session data (just as the SECRET_KEY setting from nav.conf). It should be a random string of characters; we can suggest using the makepasswd command to generate such a string:

$ makepasswd --chars 51
iLNScMiUpNy5hditWAp9e2dyHGTFoX44UKsbhj91f9xL4fdJSDY

Then edit /etc/graphite/local_settings.py (do not, under any circumstances, re-use the actual example value of SECRET_KEY here!) and make to set these three settings:

SECRET_KEY = 'iLNScMiUpNy5hditWAp9e2dyHGTFoX44UKsbhj91f9xL4fdJSDY'
TIME_ZONE = 'Europe/Oslo' # This should correspond to your actual timezone, also as in nav.conf
DATABASES = {
    'default': {
        'NAME': 'graphite',
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'USER': 'graphite',
        'PASSWORD': 'the password you made note of above',
        'HOST': 'localhost',
        'PORT': '5432'
    }
}

Now make graphite-web initialize its database schema:

sudo -u _graphite graphite-manage migrate auth --noinput
sudo -u _graphite graphite-manage migrate --run-syncdb --noinput

Configure Apache to serve the Graphite web app

In principle, you can use any web server that supports the WSGI interface. You already have Apache with mod_wsgi, so you could use that. However, if you’re on Debian 10, the graphite-web package will run on Python 3, whereas the current NAV release runs on Python 2. mod_wsgi can only support one version of Python on the same server.

The two following examples will define an Apache virtual host that will serve the Graphite web app on port 8000. Adding SSL encryption is left as an excercise for the reader (but should be unnecessary if you wisely choose to set up the server to listen only to the localhost interface).

Warning

All graphite statistics will become browseable for anyone who can access your server on port 8000. You will probably want to restrict access to this port, either by using iptables or ACLs in your routers. Or, if you do not care about browsing the web app yourself, change the Listen statement into Listen 127.0.0.1:8000, so that only the NAV installation on localhost will be able to access it.

On Debian 9 (Stretch)

Graphite-web will need its own virtualhost, so let’s add a new site config for Apache (this example is inspired by the one supplied by the graphite-web package in /usr/share/graphite-web/apache2-graphite.conf):

/etc/apache2/sites-available/graphite-web.conf
Listen 8000
<VirtualHost *:8000>

        WSGIDaemonProcess _graphite processes=1 threads=1 display-name='%{GROUP}' inactivity-timeout=120 user=_graphite group=_graphite
        WSGIProcessGroup _graphite
        WSGIImportScript /usr/share/graphite-web/graphite.wsgi process-group=_graphite application-group=%{GLOBAL}
        WSGIScriptAlias / /usr/share/graphite-web/graphite.wsgi

        Alias /content/ /usr/share/graphite-web/static/
        <Location "/content/">
                SetHandler None
        </Location>

        ErrorLog ${APACHE_LOG_DIR}/graphite-web_error.log
        LogLevel warn
        CustomLog ${APACHE_LOG_DIR}/graphite-web_access.log combined

</VirtualHost>

On Debian 10 (Buster)

Graphite-web will still need its own virtualhost, but on this version of Debian we will run the app using a uWSGI container, and define an Apache virtual host to proxy requests to this container.

First, install uWSGI and the necessary Apache modules to set up a uWSGI request proxy:

apt-get install uwsgi uwsgi-plugin-python3 libapache2-mod-proxy-uwsgi libapache2-mod-uwsgi

Then proceed to add a new uWSGI application definition:

/etc/uwsgi/apps-enabled/graphite.ini
[uwsgi]
uid = _graphite
gid = _graphite
buffer-size = 32768
chdir = /usr/share/graphite-web
env = DJANGO_SETTINGS_MODULE=graphite.settings
max-requests = 100
module = graphite.wsgi:application
plugins = python3
processes = 5
socket = 127.0.0.1:7999
touch-reload = /usr/lib/python3/dist-packages/graphite/wsgi.py

To start an application container that will listen for requests on localhost:7999, just run:

systemctl restart uwsgi

Now you’re ready to add an Apache site definition for this app:

/etc/apache2/sites-available/graphite-web.conf
Listen 8000
<VirtualHost *:8000>
        Alias /static/ /usr/share/graphite-web/static/
        <Location "/static/">
                SetHandler None
                Require all granted
        </Location>
        <Location "/">
                Options FollowSymlinks Indexes
                Require all granted
        </Location>

        ErrorLog \${APACHE_LOG_DIR}/graphite-web_error.log
        LogLevel warn
        CustomLog \${APACHE_LOG_DIR}/graphite-web_access.log combined

        ProxyRequests Off
        ProxyPreserveHost Off

        # Let Apache serve static files
        ProxyPass /static/ !
        ProxyPassReverse /static/ !
        # Give the rest to our uWSGI instance
        ProxyPass / uwsgi://127.0.0.1:7999/
        ProxyPassReverse / uwsgi://127.0.0.1:7999/

        ProxyTimeout 300
</VirtualHost>

Then make sure to enable the required Apache modules to use this site config:

a2enmod uwsgi proxy proxy_uwsgi

Finally, on both Debian versions

Enable the new site on port 8000:

a2ensite graphite-web
systemctl restart apache2

Congratulations, you should now be ready to start NAV!