How to upload file from Google App Engine to Google Cloud Storage using Python Flask?

Question

I want to upload file from Google App Engine to Google Cloud Storage I'm using Pyhton 3.8 and Flask.

app.yaml:

runtime: python38

requirements.txt

Flask==2.0.0;
google-cloud
google-cloud-storage

I tried to upload file using Flask (https://www.tutorialspoint.com/flask/flask_file_uploading.htm) to /tmp (in App Engine temporary storage (https://cloud.google.com/appengine/docs/standard/python3/using-temp-files))

Then I tried to upload from temporary storage to Google Cloud Storage using this code samples: (https://cloud.google.com/storage/docs/uploading-objects#storage-upload-object-code-sample)

but that gives me this error:

OSError: [Errno 30] Read-only file system: 'file.xlsx'

I tried from this sample too:(https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/appengine/standard/storage/api-client/main.py) and give me the same error.

Then I tried with gsutil (https://cloud.google.com/storage/docs/uploading-objects#gsutil) using subprocess.check_output (Return value of x = os.system(..)) still give me the same error.

Can anyone help me? What should I do ?

#################################################

Solved

#################################################

Thank you Edo Akse , my mistake was to use "/tmp" instead of "/tmp/", thanks a lot for helping me.

the following is the complete code which has worked.

from flask import Flask, request
from werkzeug.utils import secure_filename
from google.cloud import storage
import os

app = Flask(__name__)
app.config['UPLOAD_FOLDER'] = "/tmp/"

@app.route('/')
def index():
    page = '''
    <form action="/upload" method="post" enctype="multipart/form-data">
        <input name="file" class="custom-file-input" type="file">
        <button type="submit" class="btn btn-success">Submit</button>
    </form>
    '''
    return page

@app.route('/upload',methods=["POST"])
def upload():
    try:
        if request.method == 'POST':
            f = request.files['file']
            f.save(os.path.join(app.config['UPLOAD_FOLDER'],secure_filename(f.filename)))
            
            #Start Do Main Process Here
            TMP_FILE_NAME = os.path.join(app.config['UPLOAD_FOLDER'],secure_filename(f.filename))
            BUCKET_NAME = 'fsample123'
            result = upload_blob(BUCKET_NAME, TMP_FILE_NAME, f"tmp/{secure_filename(f.filename)}")
            #End Do Main Process Here
            return result
            
    except Exception as e:
        return str(e)

def upload_blob(bucket_name, source_file_name, destination_blob_name):
    """Uploads a file to the bucket."""
    # SOURCE:
    # https://cloud.google.com/storage/docs/uploading-objects#uploading-an-object

    # The ID of your GCS bucket
    # bucket_name = "your-bucket-name"
    # The path to your file to upload
    # source_file_name = "local/path/to/file"
    # The ID of your GCS object
    # destination_blob_name = "storage-object-name"

    storage_client = storage.Client()
    bucket = storage_client.bucket(bucket_name)
    blob = bucket.blob(destination_blob_name)
    blob.upload_from_filename(source_file_name)
    return "File {} uploaded to {}.".format(source_file_name, destination_blob_name)

if __name__ == '__main__':
   app.run()

Answer 1

So the issue is not with uploading to GCS but with the temporary file you create.

The only directory that has write access is /tmp and be aware that it is not shared between GAE instances and it disappears when the instance is restarted...

from google.cloud import storage


def upload_blob(bucket_name, source_file_name, destination_blob_name):
    """Uploads a file to the bucket."""
    # SOURCE:
    # https://cloud.google.com/storage/docs/uploading-objects#uploading-an-object

    # The ID of your GCS bucket
    # bucket_name = "your-bucket-name"
    # The path to your file to upload
    # source_file_name = "local/path/to/file"
    # The ID of your GCS object
    # destination_blob_name = "storage-object-name"

    storage_client = storage.Client()
    bucket = storage_client.bucket(bucket_name)
    blob = bucket.blob(destination_blob_name)
    blob.upload_from_filename(source_file_name)
    print(
        "File {} uploaded to {}.".format(
            source_file_name, destination_blob_name
        )
    )


TMP_PATH = "/tmp/"
TMP_FILE_NAME = f"{TMP_PATH}file.xlsx"
BUCKET_NAME = '<your-bucket-name>'


with open(TMP_FILE_NAME, "w") as outfile:
    outfile.write("write file action goes here")
upload_blob(BUCKET_NAME, TMP_FILE_NAME, "Target file path goes here...")