class org.apache.solr.update.processor.MirroringUpdateRequestProcessorFactory$MyCloseHook has interface org.apache.solr.core.CloseHook as super class

[rajanim]

Tried deploying the crossdc-producer on solr 9.x and it didn't work. The exception is as follows

org.apache.solr.common.SolrException:org.apache.solr.common.SolrException: class org.apache.solr.update.processor.MirroringUpdateRequestProcessorFactory$MyCloseHook has interface org.apache.solr.core.CloseHook as super class

the above exception looks related to the issue reported on this jira

Upgrading to 9.X allows modifying the extend to implements here as we need.
But the next compile issue comes in the ProducerMetrics class. There seems to be runtime issues that could arise from the upgrade.

Appreciate suggestions and help on this one. Thanks.

[sigram]

I think that we should move on with this project to use Solr 9x as default.