When using Lucene.Net with ASP.NET, I can imagine that one web request can trigger an update to the index while another web request is performing a search. Does Lucene.Net have built in it the ability to manage concurrent access, or do I have to manage it, to avoid "being used by another process" errors?
EDIT: After reading docs and experimentation, this is what I think I've learned: There are two issues, thread safety and concurrency. Multithreading is "safe" in that you can't do anything bad to the index. But, it's safe at the cost of just one object having a lock on the index at one time. The second object will come along and throw an exception. So, you can't leave a search open and expect a writer in another thread to be able to update the index. And if a thread is busy updating the index, then trying to create a searcher will fail.
Also, Searchers see the index as it was at the time that they open it, so if you keep them around, and update the index, they won't see the updates.
I wanted my searchers to see the latest updates.
My design, and it seems to be working so far, is that my writers and searchers share a lock, so that they don't fail – they just wait – until the current write or search is done.