Question

I’m writing a multi threaded console application which downloads pdf files from the web and copies it locally on to our content Server location(windows server). This is also the same location from which the files will be served to our website.
I am skeptical about the approach, because of concurrrency issues such as if the user on the web site requests a pdf file from the content server, and at the same time the file is being written to or being updated by the console application there might be an IO Exception. (The application also makes updates to the pdf files if the original contents change over time)
Is there a way to control the concurrency issue?

Answer 1

You probably want your operations on creating and updating the files where they are served to be atomic, so that any other processes dealing with those files get the correct version, not the one that is still open for writing.

Instead of actually writing the files to where they will be served, you could write them to a temporary directory and then move them into the directory where they will be served from.

Similarly, for updating them, you should check that when your application is updating those pdfs that the files themselves are not changed until writing has finished. You could test this by making your application sleep after it has started writing to the file, for example.