Serving ARA sqlite databases over http

Hosting statically generated reports is not very efficient at a large scale. The reports are relatively small in size but can contain thousands of files if you are generating a report that contains thousands of tasks.

However, using a centralized database (such as MySQL) might not be optimal either. Perhaps due to the latency or maybe because of the concurrency of the runs. It is also possible you are not interested in aggregating data in the first place and would rather keep individual reports.

ARA ships a bundled WSGI middleware, wsgi_sqlite.py.

This middleware allows you to store your ansible.sqlite databases on a web server (for example, a logserver for your CI jobs) and load these databases on the fly without needing to generate static reports.

It works by matching a requested URL (ex: http://logserver/some/path/ara-report) against the filesystem location (ex: /srv/static/logs/some/path/ara-report/ansible.sqlite) and loading ARA’s web application so that it reads from the database directly.

To put this use case into perspective, it was “benchmarked” against a single job from the OpenStack-Ansible project:

  • 4 playbooks
  • 4647 tasks
  • 4760 results
  • 53 hosts, of which 39 had gathered host facts
  • 416 saved files

Generating a static report from that database takes ~1min30s on an average machine. It weighs 63MB (27MB recursively gzipped), contains 5321 files and 5243 directories.

This middleware allows you to host the exact same report on your web server just by storing the sqlite database which is just one file and weighs 5.6MB.

wsgi_sqlite configuration

Configuration for the wsgi_sqlite.py script can be done through environment variables, for example with Apache’s SetEnv directive.

ARA_WSGI_USE_VIRTUALENV

Enable virtual environment usage if ARA is installed in a virtual environment. You will need to set ARA_WSGI_VIRTUALENV_PATH if enabling this.

Defaults to 0, set to 1 to enable.

ARA_WSGI_VIRTUALENV_PATH

When using a virtual environment, where the virtualenv is located. Defaults to None, set to the absolute path of your virtualenv.

ARA_WSGI_TMPDIR_MAX_AGE

This WSGI middleware creates temporary directories which should be discarded on a regular basis to avoid them accumulating. This is a duration, in seconds, before cleaning directories up.

Defaults to 3600.

ARA_WSGI_LOG_ROOT

Absolute path on the filesystem that matches the DocumentRoot of your webserver vhost.

For a DocumentRoot of /srv/static/logs, this value should be /srv/static/logs.

Defaults to /srv/static/logs.

ARA_WSGI_DATABASE_DIRECTORY

Subdirectory in which ARA sqlite databases are expected to reside in. For example, ara-report would expect: http://logserver/some/path/ara-report/ansible.sqlite.

This variable should match the WSGIScriptAliasMatch pattern of your webserver vhost.

Defaults to ara-report.

Using wsgi_sqlite with Apache’s mod_wsgi

The vhost requires you to redirect requests to */ara-report/* to the WSGI middleware. In order to do so, the vhost must look like the following:

<VirtualHost *:80>
  # Remember that DocumentRoot and ARA_WSGI_LOG_ROOT must match
  DocumentRoot /srv/static/logs
  ServerName logs.domain.tld

  ErrorLog /var/log/httpd/logs.domain.tld-error.log
  LogLevel warn
  CustomLog /var/log/httpd/logs.domain.tld-access.log combined

  SetEnv ARA_WSGI_TMPDIR_MAX_AGE 3600
  SetEnv ARA_WSGI_LOG_ROOT /srv/static/logs
  SetEnv ARA_WSGI_DATABASE_DIRECTORY ara-report
  WSGIDaemonProcess ara user=apache group=apache processes=4 threads=1
  WSGIScriptAliasMatch ^.*/ara-report /var/www/cgi-bin/ara-wsgi-sqlite
</VirtualHost>

You’ll notice the WSGIScriptAliasMatch directive pointing to the WSGI script. This is bundled when installing ARA and can be copied to the location of your choice by doing:

cp -p $(which ara-wsgi-sqlite) /var/www/cgi-bin/