Python: file-based thread-safe queue

Question

I am creating an application (app A) in Python that listens on a port, receives NetFlow records, encapsulates them and securely sends them to another application (app B). App A also checks if the record was successfully sent. If not, it has to be saved. App A waits few seconds and then tries to send it again etc. This is the important part. If the sending was unsuccessful, records must be stored, but meanwhile many more records can arrive and they need to be stored too. The ideal way to do that is a queue. However I need this queue to be in file (on the disk). I found for example this code http://code.activestate.com/recipes/576642/ but it "On open, loads full file into memory" and that's exactly what I want to avoid. I must assume that this file with records will have up to couple of GBs.

So my question is, what would you recommend to store these records in? It needs to handle a lot of data, on the other hand it would be great if it wasn't too slow because during normal activity only one record is saved at a time and it's read and removed immediately. So the basic state is an empty queue. And it should be thread safe.

Should I use a database (dbm, sqlite3..) or something like pickle, shelve or something else?

I am a little consfused in this... thank you.

Answer 1

You can use Redis as a database for this. It is very very fast, does queuing amazingly well, and it can save its state to disk in a few manners, depending on the fault tolerance level you want. being an external process, you might not need to have it use a very strict saving policy, since if your program crashes, everything is saved externally.

see here http://redis.io/documentation , and if you want more detailed info on how to do this in redis, I'd be glad to elaborate.