[ceph-users] Re: Host crash undetected by ceph health check

10 May 2021

      I reproduced the problem today by taking down the ceph cluster network interface on a host, cutting off all ceph communication at once. What I observe is, that IO gets stuck, but OSDs are not marked down. Instead, operations like the one below get stuck in the MON leader and a MON slow ops warning is shown. I thought that OSDs get marked down after a few missed heartbeats, but no such thing seems to happen. The cluster is mimic 13.2.10.

What is the expected behaviour and am I seeing something unexpected?

Thanks for any help!

        {
            "description": "osd_failure(failed timeout osd.503 192.168.32.74:6830/7639 for 66sec e468459 v468459)",
            "initiated_at": "2021-05-10 14:54:06.206619",
            "age": 116.134646,
            "duration": 88.051377,
            "type_data": {
                "events": [
                    {
                        "time": "2021-05-10 14:54:06.206619",
                        "event": "initiated"
                    },
                    {
                        "time": "2021-05-10 14:54:06.206619",
                        "event": "header_read"
                    },
                    {
                        "time": "0.000000",
                        "event": "throttled"
                    },
                    {
                        "time": "0.000000",
                        "event": "all_read"
                    },
                    {
                        "time": "0.000000",
                        "event": "dispatched"
                    },
                    {
                        "time": "2021-05-10 14:54:06.211701",
                        "event": "mon:_ms_dispatch"
                    },
                    {
                        "time": "2021-05-10 14:54:06.211701",
                        "event": "mon:dispatch_op"
                    },
                    {
                        "time": "2021-05-10 14:54:06.211701",
                        "event": "psvc:dispatch"
                    },
                    {
                        "time": "2021-05-10 14:54:06.211709",
                        "event": "osdmap:preprocess_query"
                    },
                    {
                        "time": "2021-05-10 14:54:06.211709",
                        "event": "osdmap:preprocess_failure"
                    },
                    {
                        "time": "2021-05-10 14:54:06.211717",
                        "event": "osdmap:prepare_update"
                    },
                    {
                        "time": "2021-05-10 14:54:06.211718",
                        "event": "osdmap:prepare_failure"
                    },
                    {
                        "time": "2021-05-10 14:54:06.211732",
                        "event": "no_reply: send routed request"
                    },
                    {
                        "time": "2021-05-10 14:55:34.257996",
                        "event": "no_reply: send routed request"
                    },
                    {
                        "time": "2021-05-10 14:55:34.257996",
                        "event": "done"
                    }
                ],
                "info": {
                    "seq": 34455802,
                    "src_is_mon": false,
                    "source": "osd.373 192.168.32.73:6806/7244",
                    "forwarded_to_leader": false
                }
            }
        }

=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14

________________________________________
From: Frank Schilder <frans@dtu.dk>
Sent: 07 May 2021 22:06:38
To: ceph-users@ceph.io
Subject: [ceph-users] Host crash undetected by ceph health check

Dear cephers,

today it seems I observed an impossible event for the first time: an OSD host crashed, but the ceph health monitoring did not recognise the crash. Not a single OSD was marked down and IO simply stopped, waiting for the crashed OSDs to respond. All that was reported was slow ops, slow meta data IO, MDS behind on trimming, but no OSD fail. I have rebooted these machines a lot of times and have never seen the health check fail to recognise that instantly. The only difference I see is that these were clean shut-downs, not crashes (I believe the OSDs mark themselves as down).

For debugging this problem, can anyone provide me with a pointer when this could be the result of a misconfiguration?

Thanks and best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
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