The Belle II Conditions Database (CDB) is a critical component of its infrastructure. As of early 2019 it was operated and monitored by means of a small suite of command line tools. In order to make the information contained in this database more accessible to both the database team as well as end users it was decided to create a web application (codename "CDBweb"). It aims to provide fast, easy and intuitive way to browse, inspect and verify the conditions data at varying levels of detail.
CDBweb is based on the Django web framework. At the time of writing the versions used are Django 2.1 and Python 3.6. Since the conditions database already existed and was in production when this development started, we used DB introspection to create Django models. The database tables are not managed by Django, as is often the case when one has to instrument a legacy database.
CDBweb is not accessing the actual production instance of the CDB (PostgreSQL) to minimize possible interference but instead is using a streaming replica of the CDB in read-only mode.
Current platform for CDBweb is a VM running RH7.6 and hosted at BNL.
To comply with the read-only design, CDBweb is using two separate databases: one to access the actual data and another one to manage the Django internals, user and group configuration and other administrative functions. Since performance and scalability requirements for the latter database are rather modest it is implemented as sqlite.
In order to manage the database access in this configuration a Django feature called "database routers" is utilized.