Server-side programming in Azure confidential ledger

Azure confidential ledger provides server-side programming capabilities to run custom logic inside the ledger. By using these capabilities, you can extend the functionality of the ledger by writing custom code that runs in a confidential environment and interacts with the ledger's data.

You can create user defined functions (UDFs) and user defined endpoints (UDEs) to perform various operations with different levels of customization. UDFs and UDEs were previously called simple user defined functions and advanced user defined functions, respectively. After you define UDFs and UDEs, you can invoke them from the Azure confidential ledger clients to run directly inside the ledger engine.

UDFs and UDEs

Azure confidential ledger offers two server-side programming features:

  • User defined functions (UDFs): UDFs are simple custom functions that you define and execute inside the ledger. They allow you to perform simple operations by using the JavaScript API and can be integrated with the existing ledger write API. For more information, see User defined functions in Azure confidential ledger.

  • User defined endpoints (UDEs): UDEs are custom endpoints that you define and expose on a ledger application. Use these endpoints to expose more sophisticated APIs with customizable parameters, data formats, and authentication mechanisms. For more information, see User defined endpoints in Azure confidential ledger.

Here's a comparison of the main features and capabilities of UDFs and UDEs:

Capability UDFs UDEs
Run custom business logic Yes Yes
Customization of runtime arguments / parameters Yes Yes
Expose new API / endpoints No Yes
Run individual functions Yes No
Run hooks before / after a ledger entry write operation Yes No
Creation and update of custom code Yes (granular update/delete of each function) Yes (single application bundle update for all endpoints)
Custom JavaScript runtime options Yes (per each execution) Yes (globally)
Execution on backup nodes No Yes
Support multiple data formats for input and output No Yes
Custom authentication and authorization No Yes
Target scenarios Execution of simple custom logic and integration with the ledger API Advanced use cases requiring custom APIs and control over advanced JavaScript parameters

Switching between UDFs and UDEs

UDFs and UDEs are mutually exclusive features. You can't create or run UDFs if UDEs are defined, and vice versa. Use the following steps to switch between the two features.

Important

Switching between UDFs and UDEs is a destructive operation. All existing UDFs or UDEs are deleted when switching to the other feature. Back up any important data before you proceed.

From UDFs to UDEs

To switch from UDFs to UDEs, delete all existing UDFs:

  1. List all UDFs stored in the ledger using the GET /app/userDefinedFunctions API.

  2. Delete each UDF, one by one, using the DELETE /app/userDefinedFunctions/{functionId} API.

From UDEs to UDFs

To switch from UDEs to UDFs, define UDEs with empty modules and endpoints definitions.

  1. Create a new application bundle with the following structure:

    {
    "metadata": {
        "endpoints": {}
    }, 
   "modules": []
}

  2. Deploy the application bundle with the request body defined in step 1 using the PUT /app/userDefinedEndpoints API.

Next steps

To get started with server-side programming in Azure confidential ledger, see the following articles:

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