I've noticed a problem with ezFind while scaling. It seams I have no option to tell ezFind to read from one Solr server and write to another. When all web frontends have own instance of Solr in slave mode they will also try to write into those slaves. Slaves are replicated from Master every 60sec and any local change will be overwritten in this time frame. It leads to inconsistency of the search index.

As an example sobody tries to remove an object via admin panel. Load balancer takes him to the WebServer1. He removes the object and extension/ezfind/search/plugins/ezsolr/ezsolr.php script removes it from Solr. Unfortunately object is removed only on the localhost Solr. Solr synchronize with Master server and all changes are gone. Object is not in system anymore but ezfind still returns it as search result.

Steps to reproduce

Install 2 Solr servers: Solr1 (slave), Solr2 (master)
Setup replication and run servers.
Attach ezPublish to Solr1.
Create content.

Object will be indexed locally and lost after sync.