We have an issue happening every once and while related to the connection between the CD servers and the solr which is causing some pages to go down and show empty results. 

We found that the CM is working fine while the issue is happening on CD, and sometimes it is happening on one CD only, we checked the connection between the CD servers and the solr one and everything looks good and nothing seems related to the firewall or related to the connection between the CDs and the solr server. This is the error in the log files:  

Exception: SolrNet.Exceptions.SolrConnectionException
Message: Unable to connect to the remote server
Source: SolrNet
at SolrNet.Impl.SolrConnection.Get(String relativeUrl, IEnumerable`1 parameters)
at SolrNet.Impl.SolrQueryExecuter`1.Execute(ISolrQuery q, QueryOptions options)
at Sitecore.ContentSearch.SolrProvider.LinqToSolrIndex`1.GetResult(SolrCompositeQuery compositeQuery, QueryOptions queryOptions)
Nested Exception

  we solve the issue by recycling the app pool on the CD servers.

so not sure if this is something you experienced before?

Sitecore version is 9.2.0   Thanks

  • can you check the memory you provided to Solr? If it not good enough, Solr will throw memory heap errors.
    – Jonathan
    Aug 13, 2021 at 12:44

1 Answer 1


Yes, we met this issue before, while it's in internal network environment and with VPN. Not sure if you are within exactly the same situation. What we did and verified the root cause is as below:

  1. Check the solr logs to see if any error/warning/exception (seems you did already), but please also confirm if the error is consistently available or just for once when you call the solr service.
  2. If it's been existing all along ,we suggest to check the network connection. check if any network latency or packet loss which may cause this issue. you can use PING command to insist connect between CD server and Solr server. At least 1000 times to check the packet loss percentage. (We are with this case and we tried to switch one VPC and fixed this issue)
  3. Check the solr service dashboard to check if any configuration is missing or set up inccorectly, especially when you are using Solr Cloud or Solr replica.
  4. Also you can check if any firewall rules or port is blocking this by mistake. Moreover,you can raise a ticket to Sitecore Support to get further assitance.

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