query-function.md

Query functions

Query functions are async functions written in JavaScript that will be executed in a Remote-func engine. This bring new possibilities to front-end, and backend developers allowing the front-end to evolve with more independency from the back-end. Query functions can be compared to PostgreSQL DO statement, and Redis eval.

Query functions are very restrictive because security reasons. These must be async functions, and only have access to endpoints and the following read only globals:

• Promise
• Object
• Date
• Array
• Number
• String

Cfunc

Cfunc is inspired by Linux cgroups. This is the tool that allow to run safe JavaScript in server side. Cfunc transpiles the query source code transforming it in a safe runnable code.

Execution runtime

Queries source code is transpiled so the code execution can be supervised by a runtime that watches execution time and memory allocation, restricting that query to only use the configured amount of time and memory.

Endpoint isolation

Endpoints are wrapped with ES proxies. The values returned by Endpoints will be deep-cloned. The clone process supports a limited set of JS types, those are:

• Primitive Values
• Object
• Array
• Date
• Promise(Thenables in general)

Any other type not included in the previous list will be ignored. For example, if an endpoint returns a function, it will be ignored during the cloning process, returning undefined.

Example:

// API
const api = {
  getBook: () => ({
    name: 'John',
    getName() {
      return this.name
    }
  })
}

// correct remote function
const rf1 = func(`async() => (await getBook()).name`)

// remote function with error
const rf2 = func(`async() => (await getBook()).getName()`)