Online，I call "rs.remove()"  repeatedly，mongos will print huge amounts of log like this（1GB+ logs everyminute

）：

2020-05-25T18:30:42.175+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Connecting to 127.0.0.1:15452
2020-05-25T18:30:42.175+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Connecting to 127.0.0.1:15452
2020-05-25T18:30:42.175+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Failed to connect to 127.0.0.1:15452 - HostUnreachable: Connection refused
2020-05-25T18:30:42.175+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176106 finished with response: HostUnreachable: Connection refused
2020-05-25T18:30:42.175+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176106, db:admin, request.cmdobj: { isMaster: 1 },request.metadata:{}
2020-05-25T18:30:42.175+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Dropping all pooled connections to 127.0.0.1:15452 due to failed operation on a connection
2020-05-25T18:30:42.175+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Failed to connect to 127.0.0.1:15452 - HostUnreachable: Connection refused
2020-05-25T18:30:42.176+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176107 finished with response: HostUnreachable: Connection refused
2020-05-25T18:30:42.176+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176107, db:admin, request.cmdobj: { isMaster: 1 },request.metadata:{}
2020-05-25T18:30:42.176+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Connecting to 127.0.0.1:15452
2020-05-25T18:30:42.176+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Connecting to 127.0.0.1:15452
2020-05-25T18:30:42.177+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Failed to connect to 127.0.0.1:15452 - HostUnreachable: Connection refused
2020-05-25T18:30:42.177+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176108 finished with response: HostUnreachable: Connection refused
2020-05-25T18:30:42.177+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176108, db:admin, request.cmdobj: { isMaster: 1 },request.metadata:{}
2020-05-25T18:30:42.177+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Dropping all pooled connections to 127.0.0.1:15452 due to failed operation on a connection
2020-05-25T18:30:42.177+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Failed to connect to 127.0.0.1:15452 - HostUnreachable: Connection refused
2020-05-25T18:30:42.177+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176109 finished with response: HostUnreachable: Connection refused
2020-05-25T18:30:42.177+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176109, db:admin, request.cmdobj: { isMaster: 1 },request.metadata:{}
2020-05-25T18:30:42.178+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Connecting to 127.0.0.1:15452
2020-05-25T18:30:42.178+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Connecting to 127.0.0.1:15452
2020-05-25T18:30:42.179+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Failed to connect to 127.0.0.1:15452 - HostUnreachable: Connection refused
2020-05-25T18:30:42.179+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176110 finished with response: HostUnreachable: Connection refused
2020-05-25T18:30:42.179+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176110, db:admin, request.cmdobj: { isMaster: 1 },request.metadata:{}
2020-05-25T18:30:42.179+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Dropping all pooled connections to 127.0.0.1:15452 due to failed operation on a connection
2020-05-25T18:30:42.179+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Failed to connect to 127.0.0.1:15452 - HostUnreachable: Connection refused
2020-05-25T18:30:42.179+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176111 finished with response: HostUnreachable: Connection refused
2020-05-25T18:30:42.179+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176111, db:admin, request.cmdobj: { isMaster: 1 },request.metadata:{}
2020-05-25T18:30:42.179+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Connecting to 127.0.0.1:15452
2020-05-25T18:30:42.179+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Connecting to 127.0.0.1:15452
2020-05-25T18:30:42.180+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Failed to connect to 127.0.0.1:15452 - HostUnreachable: Connection refused
2020-05-25T18:30:42.180+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176112 finished with response: HostUnreachable: Connection refused
2020-05-25T18:30:42.180+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176112, db:admin, request.cmdobj: { isMaster: 1 },request.metadata:{}
2020-05-25T18:30:42.180+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Dropping all pooled connections to 127.0.0.1:15452 due to failed operation on a connection
2020-05-25T18:30:42.180+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Failed to connect to 127.0.0.1:15452 - HostUnreachable: Connection refused
2020-05-25T18:30:42.180+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176113 finished with response: HostUnreachable: Connection refused
2020-05-25T18:30:42.180+0800 D ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Request 176113, db:admin, request.cmdobj: { isMaster: 1 },request.metadata:{}
2020-05-25T18:30:42.180+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Connecting to 127.0.0.1:15452
2020-05-25T18:30:42.180+0800 I ASIO [NetworkInterfaceASIO-TaskExecutorPool-0-0] Connecting to 127.0.0.1:15452

I reproduce the problem local.

1.mongos set db.getMongo().setReadPref('secondary')

2.make breakpoint at   NetworkInterfaceASIO::_asyncRunCommand  ‘s

asyncSendMessage(cmd->conn().stream(), &cmd->toSend(), std::move(sendMessageCallback));

3.exec find operate，like：db.test.find()

4.when hit the  breakpoint（step 2）， shutdown the secondary which the find operate target。

5.Then  huge amounts of log will print and will not stop。