We are wanting to replace our current update system for the POS software at our stores. Currently, we have a folder on our webserver that hosts a script that our registers call every 30 minutes or so. They pass in their current version number, and the server returns an XML response containing any files that need to be updated, hash, and any other pertinent information for the register to download the updated files.
We want a service that will listen for UDP packets that we send out that we can use to trigger an update. This will keep the registers from unnecessarily polling for updates. We are writing an update server that will listen for a TCP connection from a machine, authenticate, do some logging, and then send along updates for the files that have changed. We want to move to a custom update server, because we have the need to release versions of the POS to certain machines for a trial run after testing before releasing it company-wide.
I’ve written the code to handle incoming connections and create a new thread to handle communicating with that client, etc, but I am having a hard time with handling file I/O in a multithreaded manner.
I’m pretty sure I won’t be able to just access a file by opening it from one thread if it’s already open in another. I don’t want to read the files into memory and keep them in a threadsafe container beforehand, since that would use a lot of memory, especially if it turns out I need to keep a copy for each thread in order to avoid threading issues.
What would be the best way to go about being able to access these files from disk/memory in a thread-safe manner without using a lot of memory or causing threads to wait on other threads to finish with the files?
EDIT: Forgot to mention we are using C#.
Multiple threads can open a file if it’s for reading only. Just set your file mode correctly.
You will get errors (on Windows at least) if two threads try and open a read/write handle to a file.