How about a direct solution with a reference count scheme? Segments files could be reference-counted, as well as individual segments either directly, possibly by interning SegmentInfo instances, or indirectly by reference counting all files via Directory.
The most recent checkpoint and snapshot would have an implicit reference since they can be opened. Each reader and writer creates a reference when it opens a segments file. This way segments files and each segment's files would be deleted precisely when they are no longer used, which would both support NFS and improve performance on Windows. Chuck Marvin Humphrey wrote on 01/18/2007 11:40 AM: > > I wrote: >> I'd be cool with making it impossible to put an index on an NFS >> volume prior to version 4. > > Elaborating and clarifying... > > IndexReader attempts to establish a read lock on the relevant > segments_N file. It doesn't bother to see whether the locking attempt > succeeds, though. > > IndexFileDeleter, before deleting any files, always touches a test > file, attempts to lock it, and verifies that the lock succeeds. If > the locking test fails, it throws an exception rather than proceed. > > In addition, the locking test is run at index creation time, so that > the user knows as soon as possible that their index is in a > problematic location. > > I think the only way this would fail under NFS is if the client > machine with the reader is using NFS version 3, while the machine with > the writer is using version 4. But before this issue arose I didn't > have that much experience with the intricacies of NFS, so I could be > off-base. > > This does bring back the permissions issue with IndexReader. A search > app may not have permission to establish a read lock on a file within > the index directory, and in that case, an IndexFileDeleter could > delete files out from under it. > > Marvin Humphrey > Rectangular Research > http://www.rectangular.com/ > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
