Hi everyone, After some investigation, it looks like on our large cluster, ceph-mgr is not able to keep up with the status updates from about 3500 OSDs. By default OSDs send updates to ceph-mgr every 5 seconds, which, in our case, turns to about 700 messages/s to ceph-mgr. It looks from gdb traces that ceph-mgr runs some python code for each of them - so 700 python snipets/s might be too much. Increasing mgr_stats_period to 15 seconds reduces the load and brings ceph-mgr back to responsive again. Unfortunately this isn't sustainable since if we were to expand the cluster, we'd need to further reduce the update frequency from OSDs. I also checked our other clusters and they have about proportionately lower load on ceph-mgr based on their OSD counts. Any thoughts about the scalability of ceph-mgr to a large number of OSDs? We recently upgraded this cluster from Mimic, where we didn't see this issue. Andras On 5/1/20 8:48 AM, Andras Pataki wrote:
Also just a follow-up on the misbehavior of ceph-mgr. It looks like the upmap balancer is not acting reasonably either. It is trying to create upmap entries every minute or so - and claims to be successful, but they never show up in the OSD map. Setting the logging to 'debug', I see upmap entries created such as:
2020-05-01 08:43:07.909 7fffca074700 4 mgr[balancer] ceph osd pg-upmap-items 9.60c4 mappings [{'to': 3313L, 'from': 3371L}] 2020-05-01 08:43:07.909 7fffca074700 4 mgr[balancer] ceph osd pg-upmap-items 9.632b mappings [{'to': 2187L, 'from': 1477L}] 2020-05-01 08:43:07.909 7fffca074700 4 mgr[balancer] ceph osd pg-upmap-items 9.6b9c mappings [{'to': 3315L, 'from': 3371L}] 2020-05-01 08:43:07.909 7fffca074700 4 mgr[balancer] ceph osd pg-upmap-items 9.6bf6 mappings [{'to': 1581L, 'from': 1477L}] 2020-05-01 08:43:07.909 7fffca074700 4 mgr[balancer] ceph osd pg-upmap-items 9.7da4 mappings [{'to': 2419L, 'from': 2537L}] ... 2020-05-01 08:43:07.909 7fffca074700 20 mgr[balancer] commands [<mgr_module.CommandResult object at 0x7fffcc990550>, <mgr_module.CommandResult object at 0x7fffcc990fd0>, <mgr_module.CommandResult object at 0x7fffcc9907d0>, <mgr_module.Com mandResult object at 0x7fffcc990650>, <mgr_module.CommandResult object at 0x7fffcc990610>, <mgr_module.CommandResult object at 0x7fffcc990f50>, <mgr_module.CommandResult object at 0x7fffcc990bd0>, <mgr_module.CommandResult object at 0x7ff fcc990d90>, <mgr_module.CommandResult object at 0x7fffcc990ad0>, <mgr_module.CommandResult object at 0x7fffcc990410>, <mgr_module.CommandResult object at 0x7fffbed241d0>, <mgr_module.CommandResult object at 0x7fff6a6caf90>, <mgr_module.Co mmandResult object at 0x7fffbed242d0>, <mgr_module.CommandResult object at 0x7fffbed24d90>, <mgr_module.CommandResult object at 0x7fffbed24d50>, <mgr_module.CommandResult object at 0x7fffbed24550>, <mgr_module.CommandResult object at 0x7f ffbed245d0>, <mgr_module.CommandResult object at 0x7fffbed24510>, <mgr_module.CommandResult object at 0x7fffbed24690>, <mgr_module.CommandResult object at 0x7fffbed24990>] ... 2020-05-01 08:43:16.733 7fffca074700 20 mgr[balancer] done ...
but these mappings do not show up in the osd dump. And a minute later, the balancer tries again and comes up with a set of very similar mappings (same from and to OSDs, slightly different PG numbers) - and keeps going like that every minute without any progress (the set of upmap entries stays the same, does not increase).
Andras
On 5/1/20 8:12 AM, Andras Pataki wrote:
I'm wondering if anyone still sees issues with ceph-mgr using CPU and being unresponsive even in recent Nautilus releases. We upgraded our largest cluster from Mimic to Nautilus (14.2.8) recently - it has about 3500 OSDs. Now ceph-mgr is constantly at 100-200% CPU (1-2 cores), and becomes unresponsive after a few minutes. The finisher-Mgr queue length grows (I've seen it at over 100k) - similar symptoms as seen with earlier Nautilus releases by many. This is what it looks like after an hour of running:
"finisher-Mgr": { "queue_len": 66078, "complete_latency": { "avgcount": 21, "sum": 2098.408767721, "avgtime": 99.924227034 } },
We have a pretty vanilla manager config, only the balancer is enabled in upmap mode. Here are the enabled modules:
"always_on_modules": [ "balancer", "crash", "devicehealth", "orchestrator_cli", "progress", "rbd_support", "status", "volumes" ], "enabled_modules": [ "restful" ],
Any ideas or outstanding issues in this area?
Andras