Upload multiple files with storage limit in database

Question

I am currently working on a project, building a web application using C#, MSSQL and Angular. I have implemented file upload via drag and drop, and also multiple file upload, also via drag and drop. When the files are dropped, I use angular to send an API request to the server to save the file. I post the files to the server one by one.

Now, each user has only a limited amount of storage that he can use, the amount that he has already used is saved in the database.

Now what happens. The user drag and drops 4-5 files at once. The size you get from summing the file sizes of these files is larger than the amount of memory the user has the right to use.

However, all of the files are saved, because they pass the check one by one, and one by one are saved to the database... what I have is a race issue. If the check for the second file is, by chance, performed after the first file is saved, it will not pass (eg). If not, then the check will pass, and the user will exceed the amount of storage that was given to him.

Do you have any advice on how to fix the issue?

I hope everything is clear, I don't think putting code would be of much help.

Thank you all in advance.

Answer 1

iMHO, we can maintain a session variable that gets initialized with the user limit (probably during the login) and keeps on appending to for each upload.

So on receipt of a new file, you increment the size and check to see if its allowed, if so, go ahead, else throw a limit exceeded exception.

May work with minimal effort for your scenario.