See: https://lucene.472066.n3.nabble.com/SolrServerException-Timeout-occured-while-waiting-response-from-server-tc4464632.html
Maybe this will help somebody. I was dealing with exact same problem. We are running on VMs, and all of our timeout problems went away after we switched from a 5yo VmWare version to the latest Hyper-V VMs. We also made sure that all VMs have a dedicated spindle. It appears the underlying physical disk drive (which all VMs use) was getting overloaded with reads/writes. -- Sent from: https://lucene.472066.n3.nabble.com/Solr-User-f472068.html
