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Stream inference API

Streams a chat completion response.

The inference APIs enable you to use certain services, such as built-in machine learning models (ELSER, E5), models uploaded through Eland, Cohere, OpenAI, Azure, Google AI Studio, Google Vertex AI, Anthropic, Watsonx.ai, or Hugging Face. For built-in models and models uploaded through Eland, the inference APIs offer an alternative way to use and manage trained models. However, if you do not plan to use the inference APIs to use these models or if you want to use non-NLP models, use the Machine learning trained model APIs.

Request

POST /_inference/<inference_id>/_stream

POST /_inference/<task_type>/<inference_id>/_stream

Prerequisites

Requires the monitor_inference cluster privilege (the built-in inference_admin and inference_user roles grant this privilege)
You must use a client that supports streaming.

Description

The stream inference API enables real-time responses for completion tasks by delivering answers incrementally, reducing response times during computation. It only works with the completion task type.

Path parameters

<inference_id>: (Required, string) The unique identifier of the inference endpoint.
<task_type>: (Optional, string) The type of inference task that the model performs.

Request body

input: (Required, string or array of strings) The text on which you want to perform the inference task. input can be a single string or an array.

Inference endpoints for the completion task type currently only support a single string as input.

Examples

The following example performs a completion on the example question with streaming.

resp = client.inference.stream_inference(
    task_type="completion",
    inference_id="openai-completion",
    input="What is Elastic?",
)
print(resp)

const response = await client.transport.request({
  method: "POST",
  path: "/_inference/completion/openai-completion/_stream",
  body: {
    input: "What is Elastic?",
  },
});
console.log(response);

POST _inference/completion/openai-completion/_stream
{
  "input": "What is Elastic?"
}

The API returns the following response:

event: message
data: {
  "completion":[{
    "delta":"Elastic"
  }]
}

event: message
data: {
  "completion":[{
    "delta":" is"
    },
    {
    "delta":" a"
    }
  ]
}

event: message
data: {
  "completion":[{
    "delta":" software"
  },
  {
    "delta":" company"
  }]
}

(...)

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https://www.elastic.co/guide/en/elasticsearch/reference/8.17/stream-inference-api.html