Error code 1102: "Could not open channel to server." in the var/log/qrserver.scrap file.
1102 is the error code for "Could not open channel to server.", means that the topfdispatch process the qrserver has been configured to use, is not listening to the transport port.
In such error cases the topfdispatch is most likely down so that all queries issued in the time-period will receive the 1102 error code or in addition you may see the transition error codes listed below.
Transition error may appear when fdispatch goes down and the qrserver loses the
Typical transition error codes are:
1107: "Connection failed while waiting for query result."
1110: "Connection failed while waiting for document summaries."
Restart of the topfdispatchers which can be done from the Admin GUI --> System
Such a down/up transition can be caused by a slow system (i.e a ping time out).
You could try to increase the "pingioctimeout" option by updating the file
pingioctimeout = 30000 # 30 seconds
and restarting the qrserver (nctrl stop/start qrserver) process on all nodes that are running qrserver.
To check if a server is running "qrserver" or any process, use the command