Using Intrusive Microservices to Enable Deep Customization of Multi-Tenant SaaS

Enterprise software applications need to be customized in order to meet special requirements from customers. When the customization requirements are beyond the prediction of vendors, deep customization is needed, and traditionally customers do deep customizations by directly modifying the application source code. When the applications are moving from on-premises to multi-tenant Software as a Service, directly changing code is not feasible because many customers are sharing one instance of the application code. In this paper, we present a new approach to enable deep customization on multi-tenant SaaS, using intrusive microservices. The custom code is implemented as an isolated and self-contained microservice running beside the main service, and it uses callback code to intrusively execute queries or commands inside the main service. We present the key techniques behind intrusive microservices and illustrate how turned an open source online shopping application into a deeply customizable multi-tenant service.