Solr DataImportHandler tips

• possible trick with full-import as delta-import
• import can be initialised from random Solr node, because import.properties file (see below) is shared between nodes (it is stored on ZooKeeper)

import.properties file

• holds the time of last import
• this file must exist when initialising the collection (with solrctl instancedir) and could be empty
• check its content on ZooKeeper using put
• when the first full-reindex fails, this file remains empty

Additional notes

• Error: Full Import failed:java.lang.RuntimeException: org.apache.solr.common.SolrException: No registered leader was found,​ collection:my-collection slice:shard3 - no leader of this shard was found. The leader election failed or all leaders are down.
• When node is recovering, it should abe to process new documents from import