Worker Scripts

Worker scripts are scripts that run in a controlled JavaScript environment which can be triggered via HTTP events (such as GET, POST, etc.) or CRON schedules.

Worker scripts should satisfy the following requirements:

• No fallible imports
• A default object must be exported
• Within the object, the dispatch functions should be asynchronous

If ANY of the following is met, your worker gets terminated:

• Any of the above requirements is not met
• Accumulated time for tasks between await points (in other words, tasks that are likely CPU-bound) is more than 10ms
• Wall time (the whole execution time of the worker) is more than 10s

Generally, workers should be lightweight tasks that don’t take too much time or CPU.

Example worker

Below is a simple worker that says “Hello, world!” to every HTTP request that comes in.

export default {
  // This gets called when a request comes in
  async fetch(request, env) {
    // You can do some heavy calculation, as long as the 
    // accumulated time is <10ms
    for (let i = 0; i < 100; i++) {
      Math.cos(Math.random() * Math.PI);
    }
    
    return new Response("Hello, world!", { status: 200 });
  }
};

Web API compatibility

• fetch(): General functionalities available
• ReadableStream: General functionalities available
• Response: General functionalities available
• Request: Not available/accessible