We maintain a Software as a Service (SaaS) web application that sits on top of a multi-tenant SQL Server database. There are about 200 tables in the system, this biggest with just over 100 columns in it, at last look the database was about 10 gigabytes in size. We have about 25 client companies using the application every entering their data and running reports.
The single instance architecture is working very effectively for us - we're able to design and develop new features that are released to all clients every month. Each client experience can be configured through the use of feature-toggles, data dictionary customization, CSS skinning etc.
Our typical client is a corporate with several branches, one head office and sometimes their own inhouse IT software development teams.
The problem we're facing now is that a few of the clients are undertaking their own internal projects to develop reporting, data warehousing and dashboards based on the data presently stored in our multi-tenant database. We see it as likely that the number and sophistication of these projects will increase over time and we want to cater for it effectively.
At present, we have a "lite" solution whereby we expose a secured XML webservice that clients can call to get a full download of their records from a table. They specify the table, and we map that to a purpose-built stored proc that returns a fixed number of columns. Currently clients are pulling about 20 tables overnight into a local SQL database that they manage. Some clients have tens of thousands of records in a few of these tables.
This "lite" approach has several drawbacks: 1) Each client needs to develop and maintain their own data-pull mechanism, deal with all the logging, error handling etc. 2) Our database schema is constantly expanding and changing. The stored procs they are calling have a fixed number of columns, but occasionally when we expand an existing column (e.g. turn a varchar(50) into a varchar(100)) their pull will fail because it suddenly exceeds the column size in their local database. 3) We are starting to amass hundreds of different stored procs built for each client and their specific download expectations, which is a management hassle. 4) We are struggling to keep up with client requests for more data. We provide a "shell" schema (i.e. a copy of our database with no data in it) and ask them to select the tables they need to pull. They invariably say "all of them" which compounds the changing schema problem and is a heavy drain on our resources.
Sorry for the long winded question, but what I'm looking for is an approach to this problem that other teams have had success with. We want to securely expose all their data to them in a way they can most easily use it, but without getting caught in a constant process of negotiating data exchanges and cleaning up after schema changes.
What's worked for you?
Thanks,
Michael
I've worked for a SaaS company that went through a similar exercise some years back and Web Services is the probably the best solution here. incidentally, one of your "drawbacks" is actually a benefit. Customers should be encouraged to do their own data pulls because each customer's needs on timing and amount of data will be different.
Now instead of a LITE solution, you should look at building out a WSDL with separate CRUD calls for each table and good filtering capabilities. Also, make sure you have change times for records on each table. this way a customer can hit each table and immediately pull only the records that have been updated since the last time they pulled.
Will it be easy. Not a chance, but if you want scalability, it's the only route to go.
ood luck.