This WSGI-application has three main parts: frontend (python), backend
(python) and database (SQL). The communication between frontend and backend
is designed as if mediated by an RPC mechanism (for example
Pyro4) and between backend and database we use
psycopg2. Everything is split into several realms
to separate orthogonal problems from each other like member register from
event organization. In the python code this is achieved by different classes
for each realm and in the SQL code we have different schemas for each realm.
The production instance on the CdE server is pretty similar to the VM image provided by the auto-build. So take a look there to see how everything fits together.
The python code is state-less and thus easily parallelizable. This is exploited in the frontend (where Apache does multithreading). All state is kept in the database. For accountability we always keep a user’s latest session and a record of all sessions of the last 30 days. We only allow five active sessions per account. These limits can be adjusted in the Configuration.
The basic account is referred to as persona. Each persona has access to a subset of the realms. Some attributes of an account are only meaningful in some realms.
Additionally there are API access accounts which are referred to as Droids. These do not have an associated session but instead authenticate with a token.