2009/9/24 Noble Paul നോബിള് नोब्ळ् <noble.p...@corp.aol.com>: > On Fri, Sep 25, 2009 at 4:57 AM, Chris Harris <rygu...@gmail.com> wrote: >> The ReplicationHandler (http://wiki.apache.org/solr/SolrReplication) >> has support for "backups", which can be triggered in one of two ways: >> >> 1. in response to startup/commit/optimize events (specified through >> the backupAfter tag specified in the handler's requestHandler tag in >> solrconfig.xml) >> 2. by manually hitting >> http://master_host:port/solr/replication?command=backup >> >> These backups get placed in directories named, e.g. >> "snapshot.20090924033521", inside the solr data directory. >> >> According to the docs, these backups are not necessary for replication >> to work. My question is: What use case *are* they meant to address? >> >> The first potential use case that came to mind was that maybe I would >> be able to restore my index from these snapshot directories should it >> ever become corrupted. (I could just do something like "rm -r data; mv >> snapshot.20090924033521 data".) That appears not to be one of the >> intended use cases, though; if it were, then I imagine the snapshot >> directories would contain the entire index, whereas they seem to >> contain only deltas of one form or another. > Yes, the only reason to take a backup should be for restoration/archival > They should contain all the files required for the latest commit point.
To be clear, you'd have to write your own code to make any kind of restore from these snapshot back directories possible, right? (That is, the handler itself doesn't implement any kind of "restore", nor can you restore by using simple filesystem commands like cp -r or mv.) For example, the most straightforward case would be if you limited yourself to only doing backups after each optimize; that's straightforward in that each snapshot directory should contain all the segment files required for a particular point-in-time view of the index. However, it still wouldn't contain the Lucene segments_N file, and it seems like to implement an index restore you'd need to try to reconstitute that somehow.
