Can Execute Fast Search Queries in WFE Server but Not in APP Server. Error is “Search Request Was Unable to Execute on Fast Search Server”

Question

I have a batch job in an APP server in a SharePoint Production farm that executes Fast Search queries. Basically, the batch job calls the Search web service to execute search queries.

Previously, when I run this batch job in the APP server, it's able to complete without errors.

Now, when I run the batch job in the APP server, it's throwing me the error:

The search request was unable to execute on FAST Search Server.. 
Stack Trace:    
at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)
at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)

However, when I run the batch job in the WFE server, it's able to complete without errors.

More details are: * Search Topology: 3 crawl components; 1 is at the FAST search server and the other 2 are at 2 WFE servers. 1 admin component at the FAST Search server. 1 query component at the FAST Search server. * Version: SharePoint 2010

Would greatly appreciate any ideas and suggestions on how to troubleshoot this issue!

Answer 1

After testing, I saw that there is no issue if the search query's row limit is smaller (example: 100). However, when I set my row limit to a really large number (example: 1 million because my intention was to get the total result count), that's when the error occurs. So I'll need to revise the code to retrieve results in a paged manner. Hope this helps someone. :)