Repository: vllm-project/guidellm
Issue: Health check doesn't work on Ollama and can't be turned off
Root cause: Configuration Error

**Describe the bug**
I am trying to benchmark a model deployed locally with Ollama and seem to be getting errors due to a failed healthcheck to http://localhost:11434/health.
As far as I know the /health route is not exposed by Ollama and this check won't ever pass.

**Expected behavior**
A flag to turn off the required validation to /health.
I couldn't find any flag to turn off the validation which deemed every benchmark I wanted to run to failure.

**Environment**
1. OS: MacOS Tahoe 26.1
2. Python version 3.10.19

**To Reproduce**
first I cloned the project:
`git clone https://github.com/vllm-project/guidellm.git
cd guidellm`


Then I Installed GuideLLM:
`pip install -U pip
pip install -r requirements.txt
pip install .`


Ran Ollama serving phi3:

`ollama run phi3  `


Then ran the following benchmark:
`guidellm benchmark run \
  --target http://localhost:11434/v1 \
  --backend-type openai_http \
  --model phi3:latest \
  --processor microsoft/phi-3-mini-4k-instruct \
  --rate-type constant \
  --rate 1 \
  --max-seconds 300 \
  --output-path ./results_phi3_50_100.csv \
  --data "prompt_tokens=50,output_tokens=100"
`


**Errors**
`Traceback (most recent call last):
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/guidellm/backends/openai.py", line 168, in validate
    response.raise_for_status()
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/httpx/_models.py", line 829, in raise_for_status
    raise HTTPStatusError(message, request=request, response=self)
httpx.HTTPStatusError: Client error '404 Not Found' for url 'http://localhost:11434/health'
For more information check: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/404

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/alons/miniconda3/envs/guide_bench/bin/guidellm", line 7, in <module>
    sys.exit(cli())
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/click/core.py", line 1161, in __call__
    return self.main(*args, **kwargs)
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/click/core.py", line 1082, in main
    rv = self.invoke(ctx)
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/click/core.py", line 1697, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/click/core.py", line 1697, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/click/core.py", line 1443, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/click/core.py", line 788, in invoke
    return __callback(*args, **kwargs)
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/guidellm/__main__.py", line 430, in run
    asyncio.run(
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "uvloop/loop.pyx", line 1518, in uvloop.loop.Loop.run_until_complete
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/guidellm/benchmark/entrypoints.py", line 450, in benchmark_generative_text
    backend, model = await resolve_backend(
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/guidellm/benchmark/entrypoints.py", line 118, in resolve_backend
    await backend_instance.validate()
  File "/Users/alons/miniconda3/envs/guide_bench/lib/python3.10/site-packages/guidellm/backends/openai.py", line 170, in validate
    raise RuntimeError(
RuntimeError: Backend validation request failed. Could not connect to the server or validate the backend configuration.`

**Additional context**
When I switched the commit to commit hash af897879d4957ba000c5c2099cd11ad8880bfda2 the problem **did not produce** and I successfully benchmarked my Ollama hosted Phi3


Yes, i also encountered this when i use xinference to do the test.
But you can bypass this by editting /usr/local/lib/python3.10/dist-packages/guidellm/backends/openai.py.
async def validate(self):
    """
    Skip backend health check for Xinference / custom model servers.
    """
    return

Try `--backend-kwargs '{"validate_backend":false}'`

@sjmonson  Using `--backend-kwargs '{"validate_backend":false}'` worked for me, thank you!