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Thursday, November 24, 2011 

Multi tenant challenges.

The main reason for using multitenancy is to do remove maintenance night mare.

- Customizable with css and html (to an extent) - choosing a different css file for each tenant.
- In MVC drive the views based on tenant with each view for tenant in a different folder.
- All static files are stored under tenant specific folders - which is driven via a config file.

Business logic:
- Modularize the code and enable only few modules for each tenant.
- Inversion of control - using hooks.
- Dependency injection - driving the class names from config files based on the tenant.
- Generative programming. (while deploying the tenant, use admin tool to drive some of the code).


A database for each tenant
security- database conn is different so no problem
extending - create separate columns for the tenant if required. or have prefixed extendable columns.
scaling - scale the tenant database as required.

Single database with different table prefix for each tenant

security- database table prefix is different so not much problem if there is a single db class where we append prefix.
extending - create seperate columns for the tenant if required. or have prefixed extendable columns.
scaling - move the tables as required to a different database and scale it.

Single database with same tables with tenant id key.

security- Care should be taken to ensure the security of the queries.
extending - Have extrafields up front / have a separate table where you store extended columns. as explained here.
scaling - Use horizontal partitioning for tables using partition ids.