Difference Core Reload SolR 5 vs 8

["Moll, Dr. Andreas" <Mo...@juris.de>]

Hi,

we are currently switching from SolR  5 to SolR 8.

Has the behaviour of core reload changed between these versions?
We have a production server that creates and modifies the index.
This directory is then mounted read only for the SolR servers.

With SolR 5, we could call a core reload and it always worked fine.
In SolR 8 we get the following exception if the index changed:

recht: org.apache.lucene.index.IndexNotFoundException:org.apache.lucene.index.IndexNotFoundException:
no segments* file found in LockValidatingDirectoryWrapper(NRTCachingDirectory(MMapDirectory@/mnt/solr/data/index<mailto:MMapDirectory@/mnt/solr/jpprodt3/data/solrhome-8.9/solr_recht/core_recht/data/index>
lockFactory=org.apache.lucene.store.SingleInstanceLockFactory@74282cb8; maxCacheMB=48.0 maxMergeSizeMB=4.0))
files: [_1bob.fdm, _1bob.fdt, _1bob.fdx, _1bob.fnm, _1bob.kdd, _1bob.kdi, _1bob.kdm, _1bob.nvd, _1bob.nvm, _1bob.si, _1bob.tvd, _1bob.tvm, _1bob.tvx, _1bob_Lucene80_0.dvd, _1bob_Lucene80_0.dvm, _1bob_Lucene84_0.doc, _1bob_Lucene84_0.pos, _1bob_Lucene84_0.tim, _1bob_Lucene84_0.tip, _1bob_Lucene84_0.tmd, _1boj.fdm, _1boj.fdt, _1boj.fdx, _1boj.fnm, _1boj.kdd, _1boj.kdi, _1boj.kdm, _1boj.nvd, _1boj.nvm, _1boj.si, _1boj.tvd, _1boj.tvm, _1boj.tvx, _1boj_Lucene80_0.dvd, _1boj_Lucene80_0.dvm, _1boj_Lucene84_0.doc, _1boj_Lucene84_0.pos, _1boj_Lucene84_0.tim, _1boj_Lucene84_0.tip, _1boj_Lucene84_0.tmd, _1bok.fdm, _1bok.fdt, _1bok.fdx, _1bok.fnm, _1bok.kdd, _1bok.kdi, _1bok.kdm, _1bok.nvd, _1bok.nvm, _1bok.si, _1bok.tvd, _1bok.tvm, _1bok.tvx, _1bok_Lucene80_0.dvd, _1bok_Lucene80_0.dvm, _1bok_Lucene84_0.doc, _1bok_Lucene84_0.pos, _1bok_Lucene84_0.tim, _1bok_Lucene84_0.tip, _1bok_Lucene84_0.tmd, _1bol.fdm, _1bol.fdt, _1bol.fdx, _1bol.fnm, _1bol.kdd, _1bol.kdi, _1bol.kdm, _1bol.nvd, _1bol.nvm, _1bol.si, _1bol.tvd, _1bol.tvm, _1bol.tvx, _1bol_Lucene80_0.dvd, _1bol_Lucene80_0.dvm, _1bol_Lucene84_0.doc, _1bol_Lucene84_0.pos, _1bol_Lucene84_0.tim, _1bol_Lucene84_0.tip, _1bol_Lucene84_0.tmd, _1bom.fdm, _1bom.fdt, _1bom.fdx, _1bom.fnm, _1bom.kdd, _1bom.kdi, _1bom.kdm, _1bom.nvd, _1bom.nvm, _1bom.si, _1bom.tvd, _1bom.tvm, _1bom.tvx, _1bom_Lucene80_0.dvd, _1bom_Lucene80_0.dvm, _1bom_Lucene84_0.doc, _1bom_Lucene84_0.pos, _1bom_Lucene84_0.tim, _1bom_Lucene84_0.tip, _1bom_Lucene84_0.tmd, _1boq.fdm, _1boq.fdt, _1boq.fdx, _1boq.fnm, _1boq.kdd, _1boq.kdi, _1boq.kdm, _1boq.nvd, _1boq.nvm, _1boq.si, _1boq.tvd, _1boq.tvm, _1boq.tvx, _1boq_Lucene80_0.dvd, _1boq_Lucene80_0.dvm, _1boq_Lucene84_0.doc, _1boq_Lucene84_0.pos, _1boq_Lucene84_0.tim, _1boq_Lucene84_0.tip, _1boq_Lucene84_0.tmd, _1bor.fdm, _1bor.fdt, _1bor.fdx, _1bor.fnm, _1bor.kdd, _1bor.kdi, _1bor.kdm, _1bor.nvd, _1bor.nvm, _1bor.si, _1bor.tvd, _1bor.tvm, _1bor.tvx, _1bor_Lucene80_0.dvd, _1bor_Lucene80_0.dvm, _1bor_Lucene84_0.doc, _1bor_Lucene84_0.pos, _1bor_Lucene84_0.tim, _1bor_Lucene84_0.tip, _1bor_Lucene84_0.tmd]
        at org.apache.lucene.index.IndexWriter.<init>(IndexWriter.java:1032) ~[?:?]
        at org.apache.solr.update.SolrIndexWriter.<init>(SolrIndexWriter.java:126) ~[?:?]
        at org.apache.solr.update.SolrIndexWriter.create(SolrIndexWriter.java:100) ~[?:?]
        at org.apache.solr.update.DefaultSolrCoreState.createMainIndexWriter(DefaultSolrCoreState.java:261) ~[?:?]
        at org.apache.solr.update.DefaultSolrCoreState.changeWriter(DefaultSolrCoreState.java:224) ~[?:?]
        at org.apache.solr.update.DefaultSolrCoreState.newIndexWriter(DefaultSolrCoreState.java:233) ~[?:?]
        at org.apache.solr.core.SolrCore.reload(SolrCore.java:712) ~[?:?]
        at org.apache.solr.core.CoreContainer.reload(CoreContainer.java:1721) ~[?:?]

The index directory also contained a segment file: segments_ky

How can we mitigate this behaviour?
Any help would be greatly appreciated.

Best regards

Dr. Andreas Moll
IT-Development