I _think_, and I'm really stretching here, that you'd be OK if you
shared a single
index writer amongst all the requests. Having more than one index writer
going against the same index is a definite no-no.
But atomic updates are a request (admittedly an update request) so it must be
possible,
I am thinking about trying to structure a problem as a Solr plugin. The
nature of the plugin is that it would need to read and write the lucene
index to do its work. It could not be cleanly split into URP 'over here'
and a Search Component 'over there'.
Are there invariants of Solr that would
