[SOLR-13718] SPLITSHARD using async can cause data loss

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 7.7.2, 8.1, 8.2
• Fix Version/s: 7.7.3, 8.3
• Assignee: Ishan Chattopadhyaya
• Reporter: Ishan Chattopadhyaya
• Created: 26/Aug/19 10:49
• Updated: 21/Jan/20 16:57
• Resolved: 29/Aug/19 12:26

Description

When using SPLITSHARD with async, if there are underlying failures in the SPLIT core command or other sub-commands of SPLITSHARD, then SPLITSHARD succeeds and results in two empty sub-shards.

There are various potential failures with SPLIT core command, here's a way to reproduce using a Solr 6x index in Solr 7x.

Steps to reproduce (in Solr 7x):

1. Import the attached configset, and create a collection.
2. Move in the attached data directory (index created in Solr6x) in place of the created collection's data directory. Do a collection RELOAD.
3. Issue a *:* query, we see 5 documents.
4. Issue a SPLITSHARD (async), and then issue *:*, we see 0 documents.

Check attached solr-13718-reproduce.sh script to do the same (without needing the zip file).