Multiple Databases

Hosting Multiple Databases using Apache Virtual Hosting

It is possible to use name based virtual hosting in Apache to host multiple Specify databases from a single server. The technique involves using Apache mod_macro to abstract over the server name in the Apache conf file, and mapping the server name to the database name in the wsgi config file so that it can be substituted into the DATABASE_NAME setting in the Django settings.py file.

mod_macro

For this technique Apache mod_macro will need to be installed and enabled. In Ubuntu it looks like this:

apt-get install libapache2-mod-macro
a2enmod macro

The Apache conf file

The Specify 7 repository includes a sample Apache conf file that can be modifed and linked or copied into the /etc/apache2/site-enabled directory. This configuration can be modified to use Apache macros for multiple name based hosts. Here is an example:

<Macro SpecifyVH $servername>
<VirtualHost *:80>
        ServerName $servername.specify.ku.edu

        <Directory />
                Order deny,allow
                Allow from all
                Options -Indexes
        </Directory>

        Alias /static/config    /home/anhalt/Specify/config
        Alias /static           /home/anhalt/specify7/specifyweb/frontend/static

        WSGIDaemonProcess $servername user=anhalt group=anhalt
        WSGIProcessGroup $servername

        WSGIScriptAlias / /home/anhalt/specify7/specify.ku.edu_virtual_host.wsgi

        ErrorLog ${APACHE_LOG_DIR}/$servername_error.log

        # Possible values include: debug, info, notice, warn, error, crit,
        # alert, emerg.
        LogLevel warn

        CustomLog ${APACHE_LOG_DIR}/$servername_access.log combined
</VirtualHost>
</Macro>

#Use SpecifyVH test
Use SpecifyVH plants
Use SpecifyVH lichens
Use SpecifyVH trichomycetes
Use SpecifyVH accessions
Use SpecifyVH creac
Use SpecifyVH vertebratepaleontology
Use SpecifyVH mammalogy
Use SpecifyVH invertebratepaleontology
Use SpecifyVH ichthyology
Use SpecifyVH herpetology
Use SpecifyVH entomology
Use SpecifyVH ornithology
# Use SpecifyVH botany

This configuration creates a macro that is abstracted over the variable $servername. The Use directives at the end instantiate the macro with twelve values for the server name producing twelve separate name based virtual hosts. Each virtual host creates a separate WSGI process and separate log files.

The wsgi file.

Also included in the Specify 7 repository is a sample wsgi file that can be modified and referenced from the Apache conf file. When an WSGI application is invoked it is passed an environ value which will contain the ServerName value from Apache. The wsgi file can be updated to map the server name to the database name to pass to the Specify 7 application.

# -*- python -*-
import os, sys, json

# this is needed to prevent threading issues with mod_wsgi, e.g.
# ImportError: Failed to import _strptime because the import lockis held by another thread.
# might be fixed in python 3
# see: https://code.google.com/p/modwsgi/issues/detail?id=177

from datetime import datetime
datetime.strptime('01/14/2014', '%m/%d/%Y')

# Map server name to database name
db_map = {
    'test': 'Specify6_TEST',
    'ichthyology': 'KU_Fish_Tissue',
    'plants': 'KANUVascularPlantDB',
    'lichens': 'KANULichenDB',
    'trichomycetes': 'trichomycetes_dbo_6',
    'accessions': 'kuaccessions',
    'creac': 'CReAC',
    'vertebratepaleontology': 'KUVP_dbo_6',
    'mammalogy': 'kumam_dbo_6',
    'invertebratepaleontology': 'kuinvp4_dbo_6',
    'herpetology': 'KUHerps',
    'entomology': 'entosp_dbo_6',
    'ornithology': 'KUBirds',
#    'botany': '',
}

this_dir = os.path.dirname(__file__)

sys.path.append(this_dir)
os.environ['DJANGO_SETTINGS_MODULE'] = 'specifyweb.settings'

import django.core.handlers.wsgi
django_app = django.core.handlers.wsgi.WSGIHandler()

def application(environ, start_response):
    server_name = environ['SERVER_NAME'].split('.')[0]
    # Set environment variable with database name.
    os.environ['SPECIFY_DATABASE_NAME'] = db_map[server_name]
    return django_app(environ, start_response)

The Django settings file.

Finally, the Django settings file in specify7/specifyweb/settings/ can obtain the database name from the OS environment. The following example uses the database name not just to access the correct database but also changes various other settings based on its value.

import os

# The webapp server piggy backs on the thick client.
# Set the path to a thick client installation.
THICK_CLIENT_LOCATION = '/home/anhalt/Specify'

# Set the database name to the mysql database you
# want to access. This is modified to get its value from the environment.
DATABASE_NAME = os.environ['SPECIFY_DATABASE_NAME']

DATABASE_HOST = 'dbserver.somewhere.net'
DATABASE_PORT = ''

# The master user login. Use the same values as
# you did setting up the thick client.
MASTER_NAME = 'specifymaster'
MASTER_PASSWORD = 'cantbeguessed'

# The Specify web attachement server URL.
WEB_ATTACHMENT_URL = ("http://testattachments.nhm.ku.edu:3088/web_asset_store.xml"
                      if DATABASE_NAME == 'Specify6_TEST' else
                      "http://biimages.biodiversity.ku.edu/web_asset_store.xml")

# The Specify web attachment server key.
WEB_ATTACHMENT_KEY = ("testtesttest"
                      if DATABASE_NAME == 'Specify6_TEST' else
                      "supersecret")

# The collection name to use with the web attachment server.
WEB_ATTACHMENT_COLLECTION = None  # Use collection name.

# Set to true if asset server requires auth token to get files.
WEB_ATTACHMENT_REQUIRES_KEY_FOR_GET = False

# Report runner service
REPORT_RUNNER_HOST = ''
REPORT_RUNNER_PORT = ''

# To allow anonymous use, set ANONYMOUS_USER to a Specify username
# to use for anonymous access.
if DATABASE_NAME == 'Specify6_TEST':
    ANONYMOUS_USER = 'specifyguest'
elif DATABASE_NAME in ('KU_Fish_Tissue', 'KUHerps'):
    ANONYMOUS_USER = 'guest'
else:
    ANONYMOUS_USER = None

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