"list index out of range" error in AzureML inference schema

Question

I've deployed a model using AzureML's inference cluster. I recently found that some of the requests to the model's API endpoint resulted in a 404 HTTP error involving a missing swagger.json file.

So I followed this guide in order to auto-generate the swagger.json file. But now all the requests to the endpoint result in a "list index out of range" error and it's something to do with the input_schema decorator. I just can't seem to pinpoint what the problem is exactly.

Here is a minimal recreation of my scoring script:

from inference_schema.schema_decorators import input_schema, output_schema
from inference_schema.parameter_types.standard_py_parameter_type import StandardPythonParameterType


def inference(args):
    # inference logic here
    return model_output


def init():
    global model
    model = get_model()


input_sample = StandardPythonParameterType({
    'input_1': 'some text',
    'input_2': 'some other text',
    'input_3': 'other text'
})

sample_global_parameters = StandardPythonParameterType(1.0)

output_sample = StandardPythonParameterType({
    'Results': {
        'text': 'some text',
        'model_output': [
             {
                 'entity_type': 'date',
                 'value': '05/04/2022'
             }
        ]
    }
})

@input_schema('Inputs', input_sample)
@input_schema('GlobalParameters', sample_global_parameters)
@output_schema(output_sample)

def run(Inputs, GlobalParameters):
    try:
        return inference(Inputs['input_1'], Inputs['input_2'], Inputs['input_3'])
    except Exception as e:
        error = str(e)
        return error

I've checked out this and this question but it didn't seem to help.

I tried looking at the code on GitHub as well but I still can't triangulate on the exact problem.

I'm calling the API from Postman with the default headers (I'm not adding anything). The request body looks like this:

{
    "Inputs": {
        "input_1": "some text",
        "input_2": "some other text",
        "input_3": "different text"
    },
    "GlobalParameters": 1.0
}

This is the error message from the endpoint logs:

2022-04-05 06:33:22,536 | root | ERROR | Encountered Exception: Traceback (most recent call last):
  File "/var/azureml-server/synchronous/routes.py", line 65, in run_scoring
    response, time_taken_ms = invoke_user_with_timer(service_input, request_headers)
  File "/var/azureml-server/synchronous/routes.py", line 110, in invoke_user_with_timer
    result, time_taken_ms = capture_time_taken(user_main.run)(**params)
  File "/var/azureml-server/synchronous/routes.py", line 92, in timer
    result = func(*args, **kwargs)
  File "/var/azureml-app/main.py", line 21, in run
    return_obj = driver_module.run(**arguments)
  File "/azureml-envs/azureml_e63c7c0baf9bf3d861ce5992975a467b/lib/python3.7/site-packages/inference_schema/schema_decorators.py", line 61, in decorator_input
    return user_run(*args, **kwargs)
  File "/azureml-envs/azureml_e63c7c0baf9bf3d861ce5992975a467b/lib/python3.7/site-packages/inference_schema/schema_decorators.py", line 55, in decorator_input
    args[param_position] = _deserialize_input_argument(args[param_position], param_type, param_name)
IndexError: list index out of range

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/azureml-envs/azureml_e63c7c0baf9bf3d861ce5992975a467b/lib/python3.7/site-packages/flask/app.py", line 1832, in full_dispatch_request
    rv = self.dispatch_request()
  File "/azureml-envs/azureml_e63c7c0baf9bf3d861ce5992975a467b/lib/python3.7/site-packages/flask/app.py", line 1818, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/var/azureml-server/synchronous/routes.py", line 44, in score_realtime
    return run_scoring(service_input, request.headers, request.environ.get('REQUEST_ID', '00000000-0000-0000-0000-000000000000'))
  File "/var/azureml-server/synchronous/routes.py", line 74, in run_scoring
    raise RunFunctionException(str(exc))
run_function_exception.RunFunctionException

Answer 1

Try on setting the "GlobalParameters" to any kind of floating number other than 1.0 or try to remove it and execute. Sometimes global parameters will cause the issue.

https://learn.microsoft.com/en-us/answers/questions/746784/azure-ml-studio-error-while-testing-real-time-endp.html