I am facing this issue while searching for something below is the error message "The search request was unable to execute on FAST Search Server".
I have already refer below links but not useful
I have also tried with rebooting all the server (APP, DB, FAST Search Server).
Below is the error from ULS log
Exception occurred while triggering query processor cache refresh for application e3579d0e-7d22-48f0-93eb-edb01b387140: System.ApplicationException: Error in the application. at System.Runtime.InteropServices.Marshal.ThrowExceptionForHRInternal(Int32 errorCode, IntPtr errorInfo) at Microsoft.Office.Server.Search.Query.ApplicationCacheRefresher._CacheRefreshCallback(Object state, Boolean timedOut)
Please share your thoughts and useful links. Thanks in Advance.