fix(ray_utils): ignore re-init error

[mspronesti]

Hi,
this simple PR aims at solving this annoying error raised by ray when creating multiple vllm.LLM objects

Exception: Perhaps you called ray.init twice by accident?

[WoosukKwon]

Hi @mspronesti, thanks for submitting the PR! Could you elaborate more on the error or provide a reproducible script that causes the error?

[mspronesti]

Hi @WoosukKwon,

example script:

from vllm import LLM

llm1 = LLM(model="mosaicml/mpt-30b", tensor_parallel_size=4)
llm2 = LLM(model="mosaicml/mpt-30b", tensor_parallel_size=4)

which raises

RuntimeError: Maybe you called ray.init twice by accident? This error can be suppressed by passing in 'ignore_reinit_error=True' or by calling 'ray.shutdown()' prior to 'ray.init()'.

Same happens in a notebook, re-running the cell where a single vllm.LLM object is declared (which is how I noticed it)

[zhuohan123]

LGTM! Thanks for your contribution!