Server timeout when uploading file

Once again I’m coming late to the party, but glad of the Forums here for capturing these questions for new generations of Anvil users (=me!).

So I’ve followed these docs on Media and Files, and the link to the Uploader component…

My initial code worked fine for a 20MB data file:


def upload_address_lines(self, file, **event_args):
        """This method is called when a new file is loaded into this FileLoader"""
        file = self.file_loader_1.file
        file ='_store_uploaded_media', file, "Address_Data_UK")


def _store_uploaded_media(media, custom_name):
    media_upload = app_tables.uploads.add_row(name=custom_name, media = media, datetime =  #  <<< This is "Line 38"; see error message below
    print(f"{} saved to 'uploads' database as {custom_name}.")
    return media_upload

But presumably because of some timeout designed for reglar code execution, I get the following error consistently with a larger (40MB) data file even with my fast broadband connection which I use daily for video editing and transfers of several GB at a time:

anvil.server.TimeoutError: Server code took too long at [HomePage._DeveloperTools, line 38](javascript:void(0))

Is there a way of deactivating or lengthening the timeout for such an upload please? The only workaround I’ve found so far isn’t very satisfactory because I have to manually open up the Datatable for client writes and this obviously exposes the Uploader to potential abuse, even if temporarily:

    def upload_address_lines_client_only(self, file, **event_args):
        """This method is called when a new file is loaded into this FileLoader"""
        file = self.file_loader_1.file
        media_upload = app_tables.uploads.add_row(, media = file, datetime =
        print(f"{} saved to 'uploads' database.")

Alternatively, is there any way I can programmatically permit, then immediately restrict, Datatable writes from the client e.g. based on user rights I specify?

All the best,

In case it helps, please see this post.


Aha! Thanks - Background tasks was next on my list to have a look at, so hopefully that’ll provide a solution.

All the best,

You might also want to look at

It is not the upload that times out, it’s the call to a server function that takes longer than 30 seconds:'_store_uploaded_media.

You can upload large files by first calling a server function that returns a row that is writable to the client, then assigning media to its Media Object column, then calling another server function passing the row object.

Thanks for the suggestion @stefano.menci. I tried this but unless I’m doing something wrong, it looks like your suggestion still requires me to give Client write access to the Data table I’m afraid:

anvil.server.InternalError: Permission denied: Cannot write in table 'uploads' from client code.


    def upload_via_returned_row(self, file, **event_args):
        upload_row, row_id ="_get_upload_row", "Address_Data_UK")
        file = self.file_loader_1.file
        upload_row['media'] = file  #  <<<< Error Row"_write_upload_row", upload_row, row_id)


def _get_upload_row(custom_name):
    media_upload = app_tables.uploads.add_row(name=custom_name)
    return media_upload, media_upload.get_id()
def _write_upload_row(upload_row, row_id):
    row = app_tables.uploads.get_by_id(row_id)
    row.update(media = upload_row['media']) 

That’s correct.
You either create a table that is writable from the client side or (better) you return a client_writable view containing the row you want the client to modify.

Thanks for all the suggestions but at the risk of appearing conceited I’m going to record my own simple solution to this problem which uses the built-in Anvil Uplink feature and therefore only requires code in one place (my local machine) and doesn’t require the Data table to be opened up to Client code:

import anvil.server
from anvil.tables import app_tables
from pathlib import Path


def upload_txt(file_path):
    """ Send a file directly to Anvil Data Table as media for onward emailing"""
    file_path = Path(file_path)
    with open(file_path,"r", encoding='utf-8') as file:
        blob = anvil.BlobMedia("text/plain",,
        row = app_tables.uploads.add_row(name = "Address_Data_UK", media = blob, datetime =

Simples! Thank you Anvil…


If the upload starts always from the same computer and you have control over it, then the uplink is definitely the way to go.

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