Worker

The Worker is the main function executor of the FunLess platform. In a standard deployment, there normally are as many Workers as the total number of nodes (potentially minus one, if the Core node is not used as an executor).

Each Worker embeds a WebAssembly runtime (currently Wasmtime), to instantiate and run functions. Each function is a WebAssembly module, with the addition of the several imports/exports (see below).

FunLess-compatible WebAssembly modules

As of right now, standard WebAssembly modules are not runnable by FunLess (and vice-versa, FunLess-compatible modules are not runnable by standalone runtimes), because of several requirements in terms of imported and exported functions. We list here the required imports/exports the module must satisfy.

To produce FunLess-compatible modules, we currently use language-specific wrappers, which can be found in a dedicated repository. This approach is subject to change and we plan on greatly improving the usability of the platform, by integrating the building process with our CLI and increasing compatibility with standard WebAssembly modules.

Imported functions

• __get_input_data asks the runtime to write the input data to memory. It takes a single integer as input, representing the pointer where the data will be written.

• __insert_response inserts the function's response in memory. It takes two integers as input, representing the pointer to the response, and its length.

• __insert_error same as __insert_response, used in case the function encountered an error.

• __http_request performs an HTTP request, with a JSON body and a JSON response. Takes several parameters, in the following order:

  • pointer to the response and pointer to its length, which will be populated by the runtime after the request is performed
  • pointer to the status, also populated by the runtime
  • method (an integer from 0 to 3, representing GET, POST, PUT and DELETE in this order)
  • pointer and length of the URL
  • pointer and length of the headers, codified as a string
  • pointer and length of the body

  This function will probably be scrapped, as the WASI standard has recenly included HTTP requests and socket operations, so there will be no need for a custom import.

• __console_log is a debugging function, to be removed in the future (or at least disabled in production environments). Prints the given string (identified by two integers, a pointer to the message and its length) as a debugging log on the Worker.

Exported functions

• __invoke is used by FunLess to actually run the module. This function basically extracts the input from memory using __get_input_data, runs the main function (or its equivalent) in the given language, and inserts the results in memory using __insert_response or __insert_error. __invoke takes a single integer as argument, representing the length of the function's input (generally stringified JSON).

When loading the input data, the general workflow is:

• initialize an array of length N, where N is the parameter passed to __invoke
• call __get_input_data with a pointer to the array
• parse the array as a string
• pass the string to the main function (the actual user-defined function)

__invoke also returns either 0 or 1, for success and failure respectively, after having called __insert_response (or __insert_error).

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