Erick Erickson created SOLR-4083:
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Summary: Deprecate specifying individual <core> information in
solr.xml. Possibly deprecate solr.xml entirely
Key: SOLR-4083
URL: https://issues.apache.org/jira/browse/SOLR-4083
Project: Solr
Issue Type: Improvement
Components: Schema and Analysis
Affects Versions: 4.1, 5.0
Reporter: Erick Erickson
Assignee: Erick Erickson
Spinoff from SOLR-1306. Having a solr.xml file is limiting and possibly
unnecessary. We'd gain flexibility by having an "auto-discovery", essentially
walking the directories and finding all the cores and just loading them.
Here's an issue to start the discussion of what that would look like. At this
point the way I'm thinking about it depends on SOLR-1306, which depends on
SOLR-1028, so the chain is getting kind of long.
Straw-man proposal:
1> system properties can be specified as root paths in the solr tree to start
discovery.
2> the directory walking process will stop going deep (but not wide) in the
directories whenever a solrcore.properties file is encountered. That file can
contain any of the properties currently specifiable in a <core> tag. This
allows, for instance, re-use of a single solrconfig.xml or schema.xml file
across multiple cores. I really dont want to get into having
cores-within-cores. While this latter is possible, I don't see any advantage.
You _can_ have multiple roots and there's _no_ requirement that the cores be in
the directory immediately below that root they can be arbitrarily deep.
3> I'm not quite sure what to do with the various properties in the <cores>
tag. Perhaps just require these to be system properties?
4> Notice the title. Does it still make sense to specify <3> in solr.xml but
ignore the cores stuff? It seems like so little information will be in solr.xml
if we take all the <core> tags out that we should just kill it all together.
5> Not quite sure what this means for _where_ the cores live. Is it arbitrary?
Anywyere on disk? Why not?
6> core swapping/renaming/whatever. Really, this is about how we model
persist="true" on solr.xml. It's easy if we keep solr.xml and just remove the
individual core entries. Where to put them?
7> _if_ we're supposed to persist core admin operations, it seems like we just
persist this stuff to the individual solrcore.properties files. Things like
whether it's loaded, whether its name has changed (1028 allows lazy loading).
8> This still provide the capability of your own custom CoreDescriptorProvider,
which you'll have to specify somehow. I'm not quite sure where yet.
solr.xml is really the bootstrap for the whole shootin' match. Removing it
entirely means we have to specify root directories, zk parameters, whatever
somehow. What do people think is the best option here? Leave a degenerate
solr.xml? Require system properties be set for any of these options? Currently,
the options we'll need are anything (actual or proposed) in the <solr> and
<cores> tags.
So, what the first cut at this would be, building on 1306, is a default
CoreDescriptorProvider that ignored all the <core> entries in solr.xml, walked
the tree and loaded all the cores found. I claim this is a quick thing to PoC
assuming SOLR-1306 and I'll try to provide a patch demonstrating it over the
weekend.
But mostly, this is a place to start the discussion about what this would look
like rather than have it get lost in SOLR-1306.
finally, note that I have no intention of putting any of this into 4.x at least
until we cut the 4.1/4.0.1 whatever.
And, of course, until we fully deprecate solr.xml (5.0?) the current behavior
will be the default.
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