Both RunPod official endpoints as well as custom built endpoints function by means of a worker that fetches available jobs, passes them into a handler and then returns the output.

A worker entry point is a python file containing the command runpod.serverless.start(config). An minimal worker file is shown below:

import runpod

def handler(job):
    # Handle the job and return the output
    return {"output": "Job completed successfully"}

runpod.serverless.start({"handler": handler})

The config parameter is a dictionary containing the following keys:

The handler function can either have a standard return or be a generator function. If the handler is a generator function, it will be called with the job input and the generator will be iterated over until it is exhausted.

For more complex operations where you are downloading files or making changes to the worker, it can be beneficial to refresh the worker between jobs. This can be accomplished by enabling a refresh_worker worker flag in one of two ways:

1. Enable on start with runpod.serverless.start({"handler": handler, "refresh_worker": True}), this will refresh the worker after every job return, even if the handler raises an error.

   Example:

   from runpod.serverless import start
   
   def handler(job):
       # Handle the job and return the output
       return {"output": "Job completed successfully"}
   
   start({"handler": handler, "refresh_worker": True})

2. Return refresh_worker=True as a top-level dictionary key in the handler return. This can selectively be used to refresh the worker based on the job return.

   Example:

   def handler_with_selective_refresh(job):
       if job["input"].get("refresh", False):
           # Handle the job and return the output with refresh_worker flag
           return {"output": "Job completed successfully", "refresh_worker": True}
       else:
           # Handle the job and return the output
           return {"output": "Job completed successfully"}