[FEAT] Tenants and Shells

[sfmskywalker]

Tenants & Shells

An Elsa application is composed using Shell Blueprints, which serve as the foundational templates for constructing Shells. Each Shell Blueprint comprises a collection of Features. These Features encapsulate the necessary code to configure a ServiceCollection, ensuring modular and reusable components. Think of a Feature like small Startup classes in classic ASP.NET Core MVC applications.

A Shell, derived from a Shell Blueprint, includes a ServiceCollection that is configured by its Features. Each Shell houses a ServiceProvider, constructed from the Shell's ServiceCollection. This design ensures that services within a Shell are self-contained and can be managed independently.

Tenants within the application are linked to specific Shells. The level of isolation for each Tenant is determined by its IsolationMode:

• Shared: The Tenant shares the Application's Shell, enabling resource sharing and reducing overhead.
• Isolated: The Tenant is assigned its own dedicated Shell, ensuring complete isolation and customization.

The application has the capability to update a Shell Blueprint and subsequently generate a new Shell. This dynamic feature allows for isolated tenants to be reconfigured with distinct services and configurations without impacting other tenant shells. This flexibility unlocks seamless updates and maintenance, promoting a robust and scalable multi-tenant architecture.

The above design proposal is inspired on Orchard Core's Shells system, a proven robust, modular, multi-tenant architecture.

Rationale

Implementing the Tenants and Shells system introduces a robust multi-tenant architecture to the Elsa application, inspired by the proven design of Orchard Core. This system enhances the application's flexibility, scalability, and modularity by:

• Modular Architecture: By encapsulating configurations within modular Features, the system promotes reusability and easier maintenance. Features act like small startup classes, allowing developers to add or modify functionality without affecting the entire application.

• Flexible Tenant Isolation: Offering both Shared and Isolated tenant modes provides flexibility. Shared tenants can reduce resource usage by sharing the application's Shell, while isolated tenants can have dedicated Shells for customized configurations and enhanced security.

• Dynamic Updates and Scalability: The ability to update Shell Blueprints and regenerate Shells without impacting other tenants allows for seamless updates and scaling. This ensures that the application can evolve and adapt to new requirements with minimal downtime.

• Improved Maintainability: Isolation of services within each Shell means that changes in one tenant's services do not interfere with others. This isolation simplifies debugging and enhances the overall stability of the application.

• Inspired by Proven Systems: Leveraging concepts from Orchard Core's Shells system brings in a design that has been tested and refined, reducing risks associated with architectural changes and providing a solid foundation for multi-tenant support.

By integrating this system, Elsa can better support scenarios where multiple tenants require different configurations or services, all within a single application instance. This enhances the platform's capability to serve diverse user needs, promotes efficient resource utilization, and lays the groundwork for future expansion and feature additions.

Requirements

• Develop a Shell Blueprints system to serve as foundational templates for constructing Shells.
• Design modular Features that can be attached to Shell Blueprints, encapsulating code to configure a ServiceCollection.
• Implement Shells derived from Shell Blueprints, each containing a ServiceCollection configured by its Features.
• Ensure each Shell houses its own ServiceProvider built from its ServiceCollection, providing isolation of services within each Shell.
• Create a multi-tenant system where Tenants are linked to specific Shells.
• Support tenant Isolation Modes:
  • Shared: Tenants share the application's Shell and its resources.
  • Isolated: Tenants have their own dedicated Shells for complete isolation and customization.
• Enable dynamic updates to Shell Blueprints and regeneration of Shells without impacting other tenant Shells.
• Ensure the architecture promotes a robust, modular, and scalable multi-tenant system inspired by Orchard Core's Shells.
• Provide clear documentation and example usage to illustrate how to implement and manage Tenants and Shells.

[glime-ai[bot]]

To implement a ServiceCollection per tenant in Elsa, you would need to extend the existing multi-tenancy support to include isolated service collections for each tenant. This is a non-trivial feature that would require a deep understanding of both the Elsa workflow engine and the ASP.NET Core dependency injection system.

As of my knowledge cutoff date in early 2023, Elsa Workflow does not natively support a separate ServiceCollection per tenant out of the box. However, you can achieve this by customizing the Elsa Workflow engine to support multi-tenancy at a deeper level.

Here are the steps you might consider for implementing such a feature:

1. Tenant Identification: Implement a way to identify the tenant for each request. This could be done through subdomains, URL segments, headers, or any other tenant identification strategy.

2. Tenant-Specific Service Collections: Create a mechanism to maintain a separate ServiceCollection for each tenant. This could involve creating a tenant-specific IServiceProvider or using a scoped service provider that is configured per tenant.

3. Tenant-Specific Registrations: Ensure that services can be registered per tenant. This might involve creating a custom extension method for IServiceCollection that takes the tenant context into account.

4. Tenant-Specific Middleware: Develop middleware that sets up the tenant context and ensures that the correct tenant-specific services are used for each request.

5. Tenant-Specific Configurations: Allow for tenant-specific configurations, such as different database connections or external service credentials, to be loaded based on the tenant context.

6. Tenant Lifecycle Management: Implement a way to manage the lifecycle of tenants, including creation, update, and deletion of tenant-specific service collections.

7. Documentation and Examples: Provide documentation and examples to help developers understand how to use the multi-tenant features.

8. Testing: Thoroughly test the multi-tenancy features to ensure they work correctly and do not introduce security issues.

It's important to note that implementing such a feature would require a significant amount of work and a good understanding of both Elsa and ASP.NET Core's dependency injection system. Additionally, you would need to consider the implications for existing workflows and how they would migrate to the new multi-tenant setup.

For more information on how to extend Elsa Workflow, you can refer to the official documentation and the source code on GitHub. You may also want to look into how Orchard Core implements its multi-tenancy to get some ideas on how to approach this in Elsa.

This comment was generated by Glime.