Scale a Gradio App with Ray Serve#

This guide shows how to scale up your Gradio application using Ray Serve. Keep the internal architecture of your Gradio app intact, with no code changes. Simply wrap the app within Ray Serve as a deployment and scale it to access more resources.


To follow this tutorial, you need Ray Serve and Gradio. If you haven’t already, install them by running:

$ pip install "ray[serve]"
$ pip install gradio==3.19

This tutorial uses Gradio apps that run text summarization and generation models and use Hugging Face’s Pipelines to access these models. Note that you can substitute this Gradio app for any Gradio app of your own.

First, install the transformers module.

$ pip install transformers

Quickstart: Deploy your Gradio app with Ray Serve#

This section shows an easy way to deploy your app onto Ray Serve. First, create a new Python file named Second, import GradioServer from Ray Serve to deploy your Gradio app later, gradio, and transformers.pipeline to load text summarization models.

from ray.serve.gradio_integrations import GradioServer

import gradio as gr

from transformers import pipeline

Then, write a builder function that constructs the Gradio app io. This application takes in text and uses the T5 Small text summarization model loaded using Hugging Face’s Pipelines to summarize that text.


Remember you can substitute this app with your own Gradio app if you want to try scaling up your own Gradio app.

example_input = (
    "HOUSTON -- Men have landed and walked on the moon. "
    "Two Americans, astronauts of Apollo 11, steered their fragile "
    "four-legged lunar module safely and smoothly to the historic landing "
    "yesterday at 4:17:40 P.M., Eastern daylight time. Neil A. Armstrong, the "
    "38-year-old commander, radioed to earth and the mission control room "
    'here: "Houston, Tranquility Base here. The Eagle has landed." The '
    "first men to reach the moon -- Armstrong and his co-pilot, Col. Edwin E. "
    "Aldrin Jr. of the Air Force -- brought their ship to rest on a level, "
    "rock-strewn plain near the southwestern shore of the arid Sea of "
    "Tranquility. About six and a half hours later, Armstrong opened the "
    "landing craft's hatch, stepped slowly down the ladder and declared as "
    "he planted the first human footprint on the lunar crust: \"That's one "
    'small step for man, one giant leap for mankind." His first step on the '
    "moon came at 10:56:20 P.M., as a television camera outside the craft "
    "transmitted his every move to an awed and excited audience of hundreds "
    "of millions of people on earth."

def gradio_summarizer_builder():
    summarizer = pipeline("summarization", model="t5-small")

    def model(text):
        summary_list = summarizer(text)
        summary = summary_list[0]["summary_text"]
        return summary

    return gr.Interface(
        inputs=[gr.Textbox(value=example_input, label="Input prompt")],
        outputs=[gr.Textbox(label="Model output")],

Deploying Gradio Server#

In order to deploy your Gradio app onto Ray Serve, you need to wrap your Gradio app in a Serve deployment. GradioServer acts as that wrapper. It serves your Gradio app remotely on Ray Serve so that it can process and respond to HTTP requests.

By wrapping your application in GradioServer, you can increase the number of CPUs and/or GPUs available to the application.


Ray Serve doesn’t support routing requests to multiple replicas of GradioServer, so you should only have a single replica.


GradioServer is simply GradioIngress but wrapped in a Serve deployment. You can use GradioServer for the simple wrap-and-deploy use case, but in the next section, you can use GradioIngress to define your own Gradio Server for more customized use cases.


Ray can’t pickle Gradio. Instead, pass a builder function that constructs the Gradio interface.

Using either the Gradio app io, which the builder function constructed, or your own Gradio app of type Interface, Block, Parallel, etc., wrap the app in your Gradio Server. Pass the builder function as input to your Gradio Server. Ray Serves uses the builder function to construct your Gradio app on the Ray cluster.

app = GradioServer.options(ray_actor_options={"num_cpus": 4}).bind(

Finally, deploy your Gradio Server. Run the following in your terminal:

$ serve run demo:app

Access your Gradio app at http://localhost:8000 The output should look like the following image: Gradio Result

See the Production Guide for more information on how to deploy your app in production.

Parallelizing models with Ray Serve#

You can run multiple models in parallel with Ray Serve by using model composition in Ray Serve.

Original approach#

Suppose you want to run the following program.

  1. Take two text generation models, gpt2 and distilgpt2.

  2. Run the two models on the same input text, so that the generated text has a minimum length of 20 and maximum length of 100.

  3. Display the outputs of both models using Gradio.

This code is a typical implementation:

generator1 = pipeline("text-generation", model="gpt2")
generator2 = pipeline("text-generation", model="distilgpt2")

def model1(text):
    generated_list = generator1(text, do_sample=True, min_length=20, max_length=100)
    generated = generated_list[0]["generated_text"]
    return generated

def model2(text):
    generated_list = generator2(text, do_sample=True, min_length=20, max_length=100)
    generated = generated_list[0]["generated_text"]
    return generated

demo = gr.Interface(
    lambda text: f"{model1(text)}\n------------\n{model2(text)}", "textbox", "textbox"

Launch the Gradio app with this command:


Parallelize using Ray Serve#

With Ray Serve, you can parallelize the two text generation models by wrapping each model in a separate Ray Serve deployment. You can define deployments by decorating a Python class or function with @serve.deployment. The deployments usually wrap the models that you want to deploy on Ray Serve to handle incoming requests.

Follow these steps to achieve parallelism. First, import the dependencies. Note that you need to import GradioIngress instead of GradioServer like before because in this case, you’re building a customized MyGradioServer that can run models in parallel.

from ray import serve
from ray.serve.handle import DeploymentHandle
from ray.serve.gradio_integrations import GradioIngress

import gradio as gr

import asyncio
from transformers import pipeline

Then, wrap the gpt2 and distilgpt2 models in Serve deployments, named TextGenerationModel.

class TextGenerationModel:
    def __init__(self, model_name):
        self.generator = pipeline("text-generation", model=model_name)

    def __call__(self, text):
        generated_list = self.generator(
            text, do_sample=True, min_length=20, max_length=100
        generated = generated_list[0]["generated_text"]
        return generated

app1 = TextGenerationModel.bind("gpt2")
app2 = TextGenerationModel.bind("distilgpt2")

Next, instead of simply wrapping the Gradio app in a GradioServer deployment, build your own MyGradioServer that reroutes the Gradio app so that it runs the TextGenerationModel deployments.

class MyGradioServer(GradioIngress):
    def __init__(
        self, downstream_model_1: DeploymentHandle, downstream_model_2: DeploymentHandle
        self._d1 = downstream_model_1
        self._d2 = downstream_model_2

        super().__init__(lambda: gr.Interface(self.fanout, "textbox", "textbox"))

    async def fanout(self, text):
        [result1, result2] = await asyncio.gather(
            self._d1.remote(text), self._d2.remote(text)
        return (
            f"[Generated text version 1]\n{result1}\n\n"
            f"[Generated text version 2]\n{result2}"

Lastly, link everything together:

app = MyGradioServer.bind(app1, app2)


This step binds the two text generation models, which you wrapped in Serve deployments, to MyGradioServer._d1 and MyGradioServer._d2, forming a model composition. In the example, the Gradio Interface io calls MyGradioServer.fanout(), which sends requests to the two text generation models that you deployed on Ray Serve.

Now, you can run your scalable app, to serve the two text generation models in parallel on Ray Serve. Run your Gradio app with the following command:

$ serve run demo:app

Access your Gradio app at http://localhost:8000, and you should see the following interactive interface: Gradio Result

See the Production Guide for more information on how to deploy your app in production.