我们尝试迁移到Solr8.7（从7.2开始）。我们使用solr云。我们总共有5个系列。
迁移步骤：a。使用集合API和命令backup b备份7.2上的集合。使用集合API和命令restore在8.7上还原备份。
集群启动良好，能够处理流量。但经过一段时间（几十分钟到几个小时），只有一个收藏（卖家）进入错误状态。其他所有的收藏品都很好。
请在日志中找到以下条目。我们看到搜索程序正在关闭，但无法创建新的搜索程序。这种情况发生在不同时间点（同一集合的）不同副本上。

2021-06-26 18:56:36.866 INFO  (qtp1539947037-32) [c:catalog s:shard1 r:core_node4 x:catalog_shard1_replica_n3] o.a.s.m.SolrMetricManager Closing metric reporters for registry=solr.core.sellers.shard1.replica_n3 tag=SolrCore@705ab99d
2021-06-26 18:56:36.866 INFO  (qtp1539947037-32) [c:catalog s:shard1 r:core_node4 x:catalog_shard1_replica_n3] o.a.s.m.SolrMetricManager Closing metric reporters for registry=solr.collection.sellers.shard1.leader tag=SolrCore@705ab99d
2021-06-26 18:56:36.866 WARN  (qtp1539947037-32) [c:catalog s:shard1 r:core_node4 x:catalog_shard1_replica_n3] o.a.s.c.ZkController Was asked to remove OnReconnect listener ZkIndexSchemaReader: /configs/sellers/managed-schema, uniqueCoreId:
 sellers_shard1_replica_n3:5034137196427355, but remove operation did not find it in the list of registered listeners.
2021-06-26 18:56:36.866 WARN  (qtp1539947037-32) [c:catalog s:shard1 r:core_node4 x:catalog_shard1_replica_n3] o.a.s.c.ZkController /configs/sellers has no more registered listeners, but a live one attempted to unregister!
2021-06-26 18:56:36.869 ERROR (qtp1539947037-32) [c:catalog s:shard1 r:core_node4 x:catalog_shard1_replica_n3] o.a.s.c.SolrCore java.lang.IllegalArgumentException: Unknown directory: NRTCachingDirectory(MMapDirectory@/var/solr/data/sellers_
shard1_replica_n3/data/snapshot_metadatalockFactory=org.apache.lucene.store.NativeFSLockFactory@35b829da; maxCacheMB=48

.....

**2021-06-26 18:56:36.872 ERROR (qtp1539947037-32) [c:catalog s:shard1 r:core_node4 x:catalog_shard1_replica_n3] o.a.s.h.RequestHandlerBase org.apache.solr.common.SolrException: Error opening new searcher**

        at org.apache.solr.core.SolrCore.openNewSearcher(SolrCore.java:2205)
        at org.apache.solr.core.SolrCore.getSearcher(SolrCore.java:2329)
        at org.apache.solr.core.SolrCore.getSearcher(SolrCore.java:2059)
        at org.apache.solr.search.JoinQuery$JoinQueryWeight.<init>(JoinQParserPlugin.java:345)
        at org.apache.solr.search.JoinQuery.createWeight(JoinQParserPlugin.java:304)
        at org.apache.lucene.search.IndexSearcher.createWeight(IndexSearcher.java:726)
        at org.apache.lucene.search.BooleanWeight.<init>(BooleanWeight.java:63)
        at org.apache.lucene.search.BooleanQuery.createWeight(BooleanQuery.java:231)
        at org.apache.lucene.search.IndexSearcher.createWeight(IndexSearcher.java:726)
        at org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:445)
        at org.apache.solr.search.DocSetUtil.createDocSetGeneric(DocSetUtil.java:145) 

....

**Caused by: org.apache.lucene.store.AlreadyClosedException: Already closed

        at org.apache.solr.core.CachingDirectoryFactory.get(CachingDirectoryFactory.java:343)**
        at org.apache.solr.core.SolrCore.getNewIndexDir(SolrCore.java:400)
        at org.apache.solr.core.SolrCore.openNewSearcher(SolrCore.java:2085)