On Tue, Dec 16, 2008 at 1:04 AM, Michael Stoppelman <stop...@gmail.com> wrote: > I've got a question from Doug's original email about replication ( > http://www.mail-archive.com/lucene-u...@jakarta.apache.org/msg12709.html): > > "1. On the index master, periodically checkpoint the index. Every minute or > so the IndexWriter is closed and a 'cp -lr index index.DATE' command is > executed from Java, where DATE is the current date and time. This > efficiently makes a copy of the index when its in a consistent state by > constructing a tree of hard links. If Lucene re-writes any files (e.g., the > segments file) a new inode is created and the copy is unchanged." > > Is closing the IndexWriter really a requirement on taking a snapshot? Or can > one take a snapshot on an index being written, I've done this in my > development environment and it seems to work fine w/o closing the > IndexWriter.
There are subtle race conditions if you try to do this with a changing index. At any instance in time, the index should be consistent, *but* you can't actually make a snapshot instantaneously. So this is doable, but it would require some complex retry logic like IndexReader has when opening an index. > Also the solr replication shell scripts don't seem to worry > about this either. Solr takes snapshots when it knows it's not updating the index (new index changes are internally blocked when calling snapshooter). -Yonik --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org For additional commands, e-mail: java-user-h...@lucene.apache.org
