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If your application supports user-uploaded files (such as media uploads), you’ll need a storage solution separate from the application’s local filesystem. Sevalla’s object storage is ideal for securely storing and serving these files.

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Configuration

Start by creating an object storage on Sevalla. Settings contains all the values needed for your storages settings. This example requires the following environment variables:
  • BUCKET_ENDPOINT
  • BUCKET_SECRET_KEY
  • BUCKET_ACCESS_KEY
  • BUCKET_NAME
The values for these environment variables can be found on the Sevalla object store Settings page. In the FastAPI project, the settings can be added to config.py. 
# app/core/config.py
class Settings(BaseSettings):
    model_config = SettingsConfigDict(env_file=".env",)

    SQLALCHEMY_DATABASE_URI: str = ""
    BUCKET_ENDPOINT: str = ""
    BUCKET_ACCESS_KEY: str = ""
    BUCKET_SECRET_KEY: str = ""
    BUCKET_NAME: str = ""

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Install

To upload files from FastAPI, install boto3. Sevalla’s object storage is S3-compatible, allowing the S3 client in boto3 to be used for interfacing with the object store on Sevalla. 
pip install boto3
pip freeze > requirements.txt

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Example

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Create a client with a dependency function

Before you can upload or read files in your bucket, you need to create an S3 client. This client is used for all S3-related methods. For this example, a function is added to dependencies.py and used inside any route that requires the boto3 client. 
# app/core/dependencies.py
import boto3 
from botocore.client import Config
from app.core.config import settings

def get_s3_client():
    return boto3.client(
        "s3",
        endpoint_url=settings.BUCKET_ENDPOINT,
        aws_access_key_id=settings.BUCKET_ACCESS_KEY,
        aws_secret_access_key=settings.BUCKET_SECRET_KEY,
        config=Config(signature_version='s3v4')
    )

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Upload a file

One method you can use to upload files is to take a file object (with a .read() method) and pass it to the upload_fileobj method. This adds it to the provided bucket with the supplied filename. This file object can come from using the UploadFile type. 
# app/main.py
from fastapi import FastAPI, Depends, UploadFile 
from app.core.config import settings
from app.core.dependencies import get_s3_client 

app = FastAPI()

@app.post("/") 
def upload(file: UploadFile, s3_client=Depends(get_s3_client)):
    s3_client.upload_fileobj(
        file.file, 
        settings.BUCKET_NAME, 
        file.filename
    )
    return {"filename": file.filename}

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List files

The list_objects_v2 method returns all the files in the supplied bucket. If your bucket is private, pre-signed URLs can be created to grant access to a file for a limited period. 
# app/main.py
...
@app.get("/") 
def files(s3_client=Depends(get_s3_client)):
    files = []
    response = s3_client.list_objects_v2(Bucket=settings.BUCKET_NAME)
    for item in response.get('Contents', []):
        files.append({"filename": item['Key'], "url": s3_client.generate_presigned_url(
            'get_object',
            Params={'Bucket': settings.BUCKET_NAME, 'Key': item['Key']},
            ExpiresIn=60,
        )})
    return {"files": files}