[SOLR-11292] Querying against an alias can lead to incorrect routing

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Varun Thacker
• Reporter: Varun Thacker
• Created: 27/Aug/17 13:22
• Updated: 21/Nov/19 00:42

Description

collection1 has 2 shards and 1 replica
collection2 has 8 shards and 1 replica

I have 8 nodes so collection2 is spread across all 8 , while collection1 is hosted by two nodes

If we create an alias called "collection1" and point it to "collection2".

Querying against the alias "collection1" works as expected but what I noticed was the top level queries would only hit 2 out of the 8 JVMs when querying using SolrJ

It turns out that SolrJ is using the state.json of collection1 ( the actual collection ) and routing queries to only those nodes.

There are two negatives to this:

• If those two nodes are down all queries fail.
• Top level queries are only routed to those two nodes thus causing a skew in the top level requests

The obvious solution would be to use the state.json file of the underlying collection that the alias is pointing to . But if we have the alias pointing to multiple collections then this might get tricky?

Issue Links

• is related to: SOLR-11444 Improve Aliases.java and comma delimited collection list handling