Hi all,
Ok, so I have some updates on this.
We noticed that we had a bucket with tons of RGW garbage collection pending. It was
growing faster than we could clean it up.
We suspect this was because users tried to do "s3cmd sync" operations on SWIFT
uploaded large files. This could logically cause issues as s3 and SWIFT calculate md5sums
differently on large objects.
The following command showed the pending gc, and also shows which buckets are affected.
radosgw-admin gc list |grep oid >garbagecollectionlist.txt
Our total RGW GC backlog was up to ~40 M.
We stopped the main s3sync workflow which was affecting the GC growth. Then we started
running more aggressive radosgw garbage collection.
This really helped with the memory use. It dropped a lot, and for now *knock on wood* when
the GC has been cleaned up, the memory has stayed at a more stable lower level.
So we hope we found the (or a) trigger for the problem.
Hopefully reveals another thread to pull for others debugging the same issue (and for us
when we hit it again).
Cheers,
Kalle
----- Original Message -----
From: "Dan van der Ster"
<dan(a)vanderster.com>
To: "Kalle Happonen" <kalle.happonen(a)csc.fi>
Cc: "ceph-users" <ceph-users(a)ceph.io>
Sent: Tuesday, 1 December, 2020 16:53:50
Subject: Re: [ceph-users] Re: osd_pglog memory hoarding - another case
> Hi Kalle,
>
> Thanks for the update. Unfortunately I haven't made any progress on
> understanding the root cause of this issue.
> (We are still tracking our mempools closely in grafana and in our case
> they are no longer exploding like in the incident.)
>
> Cheers, Dan
>
> On Tue, Dec 1, 2020 at 3:49 PM Kalle Happonen <kalle.happonen(a)csc.fi> wrote:
>>
>> Quick update, restarting OSDs is not enough for us to compact the db. So we
>> stop the osd
>> ceph-kvstore-tool bluestore-kv /var/lib/ceph/osd/ceph-$osd compact
>> start the osd
>>
>> It seems to fix the spillover. Until it grows again.
>>
>> Cheers,
>> Kalle
>>
>> ----- Original Message -----
>> > From: "Kalle Happonen" <kalle.happonen(a)csc.fi>
>> > To: "Dan van der Ster" <dan(a)vanderster.com>
>> > Cc: "ceph-users" <ceph-users(a)ceph.io>
>> > Sent: Tuesday, 1 December, 2020 15:09:37
>> > Subject: [ceph-users] Re: osd_pglog memory hoarding - another case
>>
>> > Hi All,
>> > back to this. Dan, it seems we're following exactly in your footsteps.
>> >
>> > We recovered from our large pg_log, and got the cluster running. A week
after
>> > our cluster was ok, we started seeing big memory increases again. I
don't know
>> > if we had buffer_anon issues before or if our big pg_logs were masking it.
But
>> > we started seeing bluefs spillover and buffer_anon growth.
>> >
>> > This led to whole other series of problems with OOM killing, which probably
>> > resulted in mon node db growth which filled the disk, which resulted in
all
>> > mons going down, and a bigger mess of bringing everything up.
>> >
>> > However. We're back. But I think we can confirm the buffer_anon growth,
and
>> > bluefs spillover.
>> >
>> > We now have a job that constatly writes 10k objects in a buckets and
deletes
>> > them.
>> >
>> > This may curb the memory growth, but I don't think it stops the problem.
We're
>> > just testing restarting OSDs and while it takes a while, it seems it may
help.
>> > Of course this is not the greatest fix in production.
>> >
>> > Has anybody gleaned any new information on this issue? Things to tweaks?
Fixes
>> > in the horizon? Other mitigations?
>> >
>> > Cheers,
>> > Kalle
>> >
>> >
>> > ----- Original Message -----
>> >> From: "Kalle Happonen" <kalle.happonen(a)csc.fi>
>> >> To: "Dan van der Ster" <dan(a)vanderster.com>
>> >> Cc: "ceph-users" <ceph-users(a)ceph.io>
>> >> Sent: Thursday, 19 November, 2020 13:56:37
>> >> Subject: [ceph-users] Re: osd_pglog memory hoarding - another case
>> >
>> >> Hello,
>> >> I thought I'd post an update.
>> >>
>> >> Setting the pg_log size to 500, and running the offline trim operation
>> >> sequentially on all OSDs seems to help. With our current setup, it takes
about
>> >> 12-48h per node, depending on the pgs per osd. The PG amounts per OSD we
have
>> >> are ~180-750, with a majority around 200, and some nodes consistently
have 500
>> >> per OSD. The limiting factor of the recovery time seems to be our nvme,
which
>> >> we use for rocksdb for the OSDs.
>> >>
>> >> We haven't fully recovered yet, we're working on it. Almost all
our PGs are back
>> >> up, we still have ~40/18000 PGs down, but I think we'll get there.
Currently
>> >> ~40 OSDs/1200 down.
>> >>
>> >> It seems like the previous mention of 32kB / pg_log entry seems in the
correct
>> >> magnitude for us too. If we count 32kB * 200 pgs * 3000 log entries,
we're
>> >> close to the 20 GB / OSD process.
>> >>
>> >> For the nodes that have been trimmed, we're hovering around 100
GB/node of
>> >> memory use, or ~4 GB per OSD, and so far seems stable, but we don't
have longer
>> >> term data on that, and we don't know exactly how it behaves when
load is
>> >> applied. However if we're currently at the pg_log limit of 500,
adding load
>> >> should hopefully not increase pg_log memory consumption.
>> >>
>> >> Cheers,
>> >> Kalle
>> >>
>> >> ----- Original Message -----
>> >>> From: "Kalle Happonen" <kalle.happonen(a)csc.fi>
>> >>> To: "Dan van der Ster" <dan(a)vanderster.com>
>> >>> Cc: "ceph-users" <ceph-users(a)ceph.io>
>> >>> Sent: Tuesday, 17 November, 2020 16:07:03
>> >>> Subject: [ceph-users] Re: osd_pglog memory hoarding - another case
>> >>
>> >>> Hi,
>> >>>
>> >>>> I don't think the default osd_min_pg_log_entries has changed
recently.
>> >>>> In
https://tracker.ceph.com/issues/47775 I proposed that we
limit the
>> >>>> pg log length by memory -- if it is indeed possible for log
entries to
>> >>>> get into several MB, then this would be necessary IMHO.
>> >>>
>> >>> I've had a surprising crash course on pg_log in the last 36
hours. But for the
>> >>> size of each entry, you're right. I counted pg log * ODS, and
did not take into
>> >>> factor pg log * OSDs * pgs on the OSD. Still the total memory use
that an OSD
>> >>> uses for pg_log was ~22GB / OSD process.
>> >>>
>> >>>
>> >>>> But you said you were trimming PG logs with the offline tool?
How long
>> >>>> were those logs that needed to be trimmed?
>> >>>
>> >>> The logs we are trimming were ~3000, we trimmed them to the new size
of 500.
>> >>> After restarting the OSDs, it dropped the pg_log memory usage from
~22GB, to
>> >>> what we guess is 2-3GB but with the cluster at this state, it's
hard to be
>> >>> specific.
>> >>>
>> >>> Cheers,
>> >>> Kalle
>> >>>
>> >>>
>> >>>
>> >>>> -- dan
>> >>>>
>> >>>>
>> >>>> On Tue, Nov 17, 2020 at 11:58 AM Kalle Happonen
<kalle.happonen(a)csc.fi> wrote:
>> >>>>>
>> >>>>> Another idea, which I don't know if has any merit.
>> >>>>>
>> >>>>> If 8 MB is a realistic log size (or has this grown for some
reason?), did the
>> >>>>> enforcement (or default) of the minimum value change lately
>> >>>>> (osd_min_pg_log_entries)?
>> >>>>>
>> >>>>> If the minimum amount would be set to 1000, at 8 MB per log,
we would have
>> >>>>> issues with memory.
>> >>>>>
>> >>>>> Cheers,
>> >>>>> Kalle
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>> ----- Original Message -----
>> >>>>> > From: "Kalle Happonen"
<kalle.happonen(a)csc.fi>
>> >>>>> > To: "Dan van der Ster"
<dan(a)vanderster.com>
>> >>>>> > Cc: "ceph-users" <ceph-users(a)ceph.io>
>> >>>>> > Sent: Tuesday, 17 November, 2020 12:45:25
>> >>>>> > Subject: [ceph-users] Re: osd_pglog memory hoarding -
another case
>> >>>>>
>> >>>>> > Hi Dan @ co.,
>> >>>>> > Thanks for the support (moral and technical).
>> >>>>> >
>> >>>>> > That sounds like a good guess, but it seems like there
is nothing alarming here.
>> >>>>> > In all our pools, some pgs are a bit over 3100, but not
at any exceptional
>> >>>>> > values.
>> >>>>> >
>> >>>>> > cat pgdumpfull.txt | jq '.pg_map.pg_stats[] |
>> >>>>> > select(.ondisk_log_size > 3100)' | egrep
"pgid|ondisk_log_size"
>> >>>>> > "pgid": "37.2b9",
>> >>>>> > "ondisk_log_size": 3103,
>> >>>>> > "pgid": "33.e",
>> >>>>> > "ondisk_log_size": 3229,
>> >>>>> > "pgid": "7.2",
>> >>>>> > "ondisk_log_size": 3111,
>> >>>>> > "pgid": "26.4",
>> >>>>> > "ondisk_log_size": 3185,
>> >>>>> > "pgid": "33.4",
>> >>>>> > "ondisk_log_size": 3311,
>> >>>>> > "pgid": "33.8",
>> >>>>> > "ondisk_log_size": 3278,
>> >>>>> >
>> >>>>> > I also have no idea what the average size of a pg log
entry should be, in our
>> >>>>> > case it seems it's around 8 MB (22GB/3000
entires).
>> >>>>> >
>> >>>>> > Cheers,
>> >>>>> > Kalle
>> >>>>> >
>> >>>>> > ----- Original Message -----
>> >>>>> >> From: "Dan van der Ster"
<dan(a)vanderster.com>
>> >>>>> >> To: "Kalle Happonen"
<kalle.happonen(a)csc.fi>
>> >>>>> >> Cc: "ceph-users"
<ceph-users(a)ceph.io>io>, "xie xingguo" <xie.xingguo(a)zte.com.cn>cn>,
>> >>>>> >> "Samuel Just" <sjust(a)redhat.com>
>> >>>>> >> Sent: Tuesday, 17 November, 2020 12:22:28
>> >>>>> >> Subject: Re: [ceph-users] osd_pglog memory hoarding
- another case
>> >>>>> >
>> >>>>> >> Hi Kalle,
>> >>>>> >>
>> >>>>> >> Do you have active PGs now with huge pglogs?
>> >>>>> >> You can do something like this to find them:
>> >>>>> >>
>> >>>>> >> ceph pg dump -f json | jq '.pg_map.pg_stats[]
|
>> >>>>> >> select(.ondisk_log_size > 3000)'
>> >>>>> >>
>> >>>>> >> If you find some, could you increase to debug_osd =
10 then share the osd log.
>> >>>>> >> I am interested in the debug lines from
calc_trim_to_aggressively (or
>> >>>>> >> calc_trim_to if you didn't enable
pglog_hardlimit), but the whole log
>> >>>>> >> might show other issues.
>> >>>>> >>
>> >>>>> >> Cheers, dan
>> >>>>> >>
>> >>>>> >>
>> >>>>> >> On Tue, Nov 17, 2020 at 9:55 AM Dan van der Ster
<dan(a)vanderster.com> wrote:
>> >>>>> >>>
>> >>>>> >>> Hi Kalle,
>> >>>>> >>>
>> >>>>> >>> Strangely and luckily, in our case the memory
explosion didn't reoccur
>> >>>>> >>> after that incident. So I can mostly only offer
moral support.
>> >>>>> >>>
>> >>>>> >>> But if this bug indeed appeared between 14.2.8
and 14.2.13, then I
>> >>>>> >>> think this is suspicious:
>> >>>>> >>>
>> >>>>> >>> b670715eb4 osd/PeeringState: do not trim pg
log past last_update_ondisk
>> >>>>> >>>
>> >>>>> >>>
https://github.com/ceph/ceph/commit/b670715eb4
>> >>>>> >>>
>> >>>>> >>> Given that it adds a case where the pg_log is
not trimmed, I wonder if
>> >>>>> >>> there could be an unforeseen condition where
`last_update_ondisk`
>> >>>>> >>> isn't being updated correctly, and
therefore the osd stops trimming
>> >>>>> >>> the pg_log altogether.
>> >>>>> >>>
>> >>>>> >>> Xie or Samuel: does that sound possible?
>> >>>>> >>>
>> >>>>> >>> Cheers, Dan
>> >>>>> >>>
>> >>>>> >>> On Tue, Nov 17, 2020 at 9:35 AM Kalle Happonen
<kalle.happonen(a)csc.fi> wrote:
>> >>>>> >>> >
>> >>>>> >>> > Hello all,
>> >>>>> >>> > wrt:
>> >>>>> >>> >
https://lists.ceph.io/hyperkitty/list/ceph-users@ceph.io/thread/7IMIWCKIHXN…
>> >>>>> >>> >
>> >>>>> >>> > Yesterday we hit a problem with osd_pglog
memory, similar to the thread above.
>> >>>>> >>> >
>> >>>>> >>> > We have a 56 node object storage
(S3+SWIFT) cluster with 25 OSD disk per node.
>> >>>>> >>> > We run 8+3 EC for the data pool (metadata
is on replicated nvme pool).
>> >>>>> >>> >
>> >>>>> >>> > The cluster has been running fine, and (as
relevant to the post) the memory
>> >>>>> >>> > usage has been stable at 100 GB / node.
We've had the default pg_log of 3000.
>> >>>>> >>> > The user traffic doesn't seem to have
been exceptional lately.
>> >>>>> >>> >
>> >>>>> >>> > Last Thursday we updated the OSDs from
14.2.8 -> 14.2.13. On Friday the memory
>> >>>>> >>> > usage on OSD nodes started to grow. On
each node it grew steadily about 30
>> >>>>> >>> > GB/day, until the servers started OOM
killing OSD processes.
>> >>>>> >>> >
>> >>>>> >>> > After a lot of debugging we found that the
pg_logs were huge. Each OSD process
>> >>>>> >>> > pg_log had grown to ~22GB, which we
naturally didn't have memory for, and then
>> >>>>> >>> > the cluster was in an unstable situation.
This is significantly more than the
>> >>>>> >>> > 1,5 GB in the post above. We do have ~20k
pgs, which may directly affect the
>> >>>>> >>> > size.
>> >>>>> >>> >
>> >>>>> >>> > We've reduced the pg_log to 500, and
started offline trimming it where we can,
>> >>>>> >>> > and also just waited. The pg_log size
dropped to ~1,2 GB on at least some
>> >>>>> >>> > nodes, but we're still recovering,
and have a lot of ODSs down and out still.
>> >>>>> >>> >
>> >>>>> >>> > We're unsure if version 14.2.13
triggered this, or if the osd restarts triggered
>> >>>>> >>> > this (or something unrelated we don't
see).
>> >>>>> >>> >
>> >>>>> >>> > This mail is mostly to figure out if there
are good guesses why the pg_log size
>> >>>>> >>> > per OSD process exploded? Any technical
(and moral) support is appreciated.
>> >>>>> >>> > Also, currently we're not sure if
14.2.13 triggered this, so this is also to
>> >>>>> >>> > put a data point out there for other
debuggers.
>> >>>>> >>> >
>> >>>>> >>> > Cheers,
>> >>>>> >>> > Kalle Happonen
>> >>>>> >>> >
_______________________________________________
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