# AI Deploy - Tutorial - Deploy an app for sentiment analysis with Hugging Face and Flask
> **Note** Access to the full documentation [here](https://docs.ovh.com/gb/en/publiccloud/ai/deploy/tuto-flask-hugging-face-sentiment-analysis/).
**Last updated 3rd November, 2022.**
> **Note**
> AI Deploy is in `beta`. During the beta-testing phase, the infrastructure’s availability and data longevity are not guaranteed. Please do not use this service for applications that are in production, as this phase is not complete.
>
> AI Deploy is covered by **[OVHcloud Public Cloud Special Conditions](https://storage.gra.cloud.ovh.net/v1/AUTH_325716a587c64897acbef9a4a4726e38/contracts/d2a208c-Conditions_particulieres_OVH_Stack-WE-9.0.pdf)**.
>
## Objective
The purpose of this tutorial is to show you how to deploy a web service for sentiment analysis on text using Hugging Face pretrained models.
In order to do this, you will use Flask, an open-source micro framework for web development in Python. You will also learn how to build and use a custom Docker image for a Flask application.
Overview of the app:
{.thumbnail}
For more information about Hugging Face, please visit .
## Requirements
- Access to the [OVHcloud Control Panel](https://www.ovh.com/auth/?action=gotomanager&from=https://www.ovh.co.uk/&ovhSubsidiary=GB);
- An AI Deploy project created inside a [Public Cloud project](https://www.ovhcloud.com/en-gb/public-cloud/) in your OVHcloud account;
- A [user for AI Deploy](https://docs.ovh.com/gb/en/publiccloud/ai/users/);
- [Docker](https://www.docker.com/get-started) installed on your local computer;
- Some knowledge about building image and [Dockerfile](https://docs.docker.com/engine/reference/builder/);
We also suggest you do some tests to find out which [Hugging Face model](https://huggingface.co/models) is right for your use case. Find examples on our [GitHub repository](https://github.com/ovh/ai-training-examples/tree/main/notebooks/natural-language-processing/text-classification/hugging-face/sentiment-analysis-twitter).
## Instructions
First, the tree structure of your folder should be as follows:
Find more information about the Flask application [here](https://flask.palletsprojects.com/en/2.0.x/quickstart/#a-minimal-application) to get ready to use it.
### Write the Flask application
Create a Python file named `app.py`.
Inside that file, import your required modules:
```python
from flask import Flask, jsonify, render_template, request, make_response
import transformers
```
Create Flask app:
```python
app = Flask(__name__)
```
Load Hugging Face models:
```python
# create a python dictionary for your models d = {: , : , ..., : }
dictOfModels = {"RoBERTa" : transformers.pipeline("sentiment-analysis", model="siebert/sentiment-roberta-large-english"), "BERT" : transformers.pipeline('sentiment-analysis', model="nlptown/bert-base-multilingual-uncased-sentiment")}
# create a list of keys to use them in the select part of the html code
listOfKeys = []
for key in dictOfModels :
listOfKeys.append(key)
```
Write the inference function:
```python
def get_prediction(message,model):
# inference
results = model(message)
return results
```
Define the GET method:
```python
@app.route('/', methods=['GET'])
def get():
# in the select we will have each key of the list in option
return render_template("home.html", len = len(listOfKeys), listOfKeys = listOfKeys)
```
Define the POST method:
```python
@app.route('/', methods=['POST'])
def predict():
message = request.form['message']
# choice of the model
results = get_prediction(message, dictOfModels[request.form.get("model_choice")])
print(f'User selected model : {request.form.get("model_choice")}')
my_prediction = f'The feeling of this text is {results[0]["label"]} with probability of {results[0]["score"]*100}%.'
return render_template('result.html', text = f'{message}', prediction = my_prediction)
```
Start your app:
```python
if __name__ == '__main__':
# starting app
app.run(debug=True,host='0.0.0.0')
```
### Write the requirements.txt file for the application
The `requirements.txt` file will allow us to write all the modules needed to make our application work. This file will be useful when writing the `Dockerfile`.
```console
Flask==1.1.2
transformers==4.4.2
torch==1.6.0
```
Here we will mainly discuss how to write the `app.py` code, the `requirements.txt` file and the `Dockerfile`. If you want to see the whole code, please refer to the [GitHub repository](https://github.com/ovh/ai-training-examples/tree/main/apps/flask/sentiment-analysis-hugging-face-app).
### Write the Dockerfile for the application
Your `Dockerfile` should start with the `FROM` instruction indicating the parent image to use. In our case we choose to start from a Python image:
```console
FROM python:3.8
```
Create the home directory and add your files to it:
```console
WORKDIR /workspace
ADD . /workspace
```
Install the `requirements.txt` file which contains your needed Python modules using a `pip install ...` command:
```console
RUN pip install -r requirements.txt
```
Define your default launching command to start the application:
```console
CMD [ "python" , "/workspace/app.py" ]
```
Give correct access rights to **ovhcloud user** (`42420:42420`):
```console
RUN chown -R 42420:42420 /workspace
ENV HOME=/workspace
```
### Build the Docker image from the Dockerfile
Launch the following command from the **Dockerfile** directory to build your application image:
```console
docker build . -t sentiment_analysis_app:latest
```
> **Note**
> The dot `.` argument indicates that your build context (place of the **Dockerfile** and other needed files) is the current directory.
>
> The `-t` argument allows you to choose the identifier to give to your image. Usually image identifiers are composed of a **name** and a **version tag** `:`. For this example we chose **sentiment_analysis_app:latest**.
>
### Test it locally (optional)
Launch the following **Docker command** to launch your application locally on your computer:
```console
docker run --rm -it -p 5000:5000 --user=42420:42420 sentiment_analysis_app:latest
```
> **Note**
> The `-p 5000:5000` argument indicates that you want to execute a port redirection from the port **5000** of your local machine into the port **5000** of the Docker container. The port **5000** is the default port used by **Flask** applications.
>
> **Warning**
> Don't forget the `--user=42420:42420` argument if you want to simulate the exact same behaviour that will occur on **AI Deploy apps**. It executes the Docker container as the specific OVHcloud user (user **42420:42420**).
>
Once started, your application should be available on `http://localhost:5000`.
### Push the image into the shared registry
> **Warning**
> The shared registry of AI Deploy should only be used for testing purposes. Please consider attaching your own Docker registry. More information about this can be found [here](https://docs.ovh.com/gb/en/publiccloud/ai/training/add-private-registry/).
>
Find the adress of your shared registry by launching this command:
```console
ovhai registry list
```
Login on the shared registry with your usual OpenStack credentials:
```console
docker login -u -p
```
Push the compiled image into the shared registry:
```console
docker tag sentiment_analysis_app:latest /sentiment_analysis_app:latest
docker push /sentiment_analysis_app:latest
```
### Launch the AI Deploy app
The following command starts a new app running your Flask application:
```console
ovhai app run --default-http-port 5000 --cpu 4 /sentiment_analysis_app:latest
```
> **Note**
> `--default-http-port 5000` indicates that the port to reach on the app URL is the `5000`.
>
> `--cpu 4` indicates that we request 4 CPUs for that app.
>
> Consider adding the `--unsecure-http` attribute if you want your application to be reachable without any authentication.
>
## Go further
- You can also imagine deploying an Object Detection model with **Flask** in this [tutorial](https://docs.ovh.com/gb/en/publiccloud/ai/deploy/web-service-yolov5/).
- Discover an other tool to deploy easily AI models: **Gradio**. Refer to this [documentation](https://docs.ovh.com/gb/en/publiccloud/ai/deploy/tuto-gradio-sketch-recognition/).