Hi,
Having spent some time on the below issue, here are the steps I took to resolve the "Large omap objects" warning. Hopefully this will help others who find themselves in this situation.
I got the object ID and OSD ID implicated from the ceph cluster logfile on the mon. I then proceeded to the implicated host containing the OSD, and extracted the implicated PG by running the following, and looking at which PG had started and completed a deep-scrub around the warning being logged:
grep -C 200 Large /var/log/ceph/ceph-osd.*.log | egrep '(Large omap|deep-scrub)'
If the bucket had not been sharded sufficiently (IE the cluster log showed a "Key Count" or "Size" over the thresholds), I ran through the manual sharding procedure (shown here: https://tracker.ceph.com/issues/24457#note-5)
Once this was successfully sharded, or if the bucket was previously sufficiently sharded by Ceph prior to disabling the functionality I was able to use the following command (seemingly undocumented for Luminous http://docs.ceph.com/docs/mimic/man/8/radosgw-admin/#commands):
radosgw-admin bi purge --bucket ${bucketname} --bucket-id ${old_bucket_id}
I then issued a ceph pg deep-scrub against the PG that had contained the Large omap object.
Once I had completed this procedure, my Large omap object warnings went away and the cluster returned to HEALTH_OK.
However our radosgw bucket indexes pool now seems to be using substantially more space than previously. Having looked initially at this bug, and in particular the first comment:
I was able to extract a number of bucket indexes that had apparently been resharded, and removed the legacy index using the radosgw-admin bi purge --bucket ${bucket} ${marker}. I am still able to perform a radosgw-admin metadata get bucket.instance:${bucket}:${marker} successfully, however now when I run rados -p .rgw.buckets.index ls | grep ${marker} nothing is returned. Even after this, we were still seeing extremely high disk usage of our OSDs containing the bucket indexes (we have a dedicated pool for this). I then modified the one liner referenced in the previous link as follows:
grep -E '"bucket"|"id"|"marker"' bucket-stats.out | awk -F ":" '{print $2}' | tr -d '",' | while read -r bucket; do read -r id; read -r marker; [ "$id" == "$marker" ] && true || NEWID=`radosgw-admin --id rgw.ceph-rgw-1 metadata get bucket.instance:${bucket}:${marker} | python -c 'import sys, json; print json.load(sys.stdin)["data"]["bucket_info"]["new_bucket_instance_id"]'`; while [ ${NEWID} ]; do if [ "${NEWID}" != "${marker}" ] && [ ${NEWID} != ${bucket} ] ; then echo "$bucket $NEWID"; fi; NEWID=`radosgw-admin --id rgw.ceph-rgw-1 metadata get bucket.instance:${bucket}:${NEWID} | python -c 'import sys, json; print json.load(sys.stdin)["data"]["bucket_info"]["new_bucket_instance_id"]'`; done; done > buckets_with_multiple_reindexes2.txt
This loops through the buckets that have a different marker/bucket_id, and looks to see if a new_bucket_instance_id is there, and if so will loop through until there is no longer a "new_bucket_instance_id". After letting this complete, this suggests that I have over 5000 indexes for 74 buckets, some of these buckets have > 100 indexes apparently.
:~# awk '{print $1}' buckets_with_multiple_reindexes2.txt | uniq | wc -l
74
~# wc -l buckets_with_multiple_reindexes2.txt
5813 buckets_with_multiple_reindexes2.txt
This is running a single realm, multiple zone configuration, and no multi site sync, but the closest I can find to this issue is this bug https://tracker.ceph.com/issues/24603
Should I be OK to loop through these indexes and remove any with a reshard_status of 2, a new_bucket_instance_id that does not match the bucket_instance_id returned by the command:
radosgw-admin bucket stats --bucket ${bucket}
I'd ideally like to get to a point where I can turn dynamic sharding back on safely for this cluster.
Thanks for any assistance, let me know if there's any more information I should provide
Chris
On Thu, 4 Oct 2018 at 18:22 Chris Sarginson <csargiso@xxxxxxxxx> wrote:
Hi,Thanks for the response - I am still unsure as to what will happen to the "marker" reference in the bucket metadata, as this is the object that is being detected as Large. Will the bucket generate a new "marker" reference in the bucket metadata?I've been reading this page to try and get a better understanding of thisHowever I'm no clearer on this (and what the "marker" is used for), or why there are multiple separate "bucket_id" values (with different mtime stamps) that all show as having the same number of shards.If I were to remove the old bucket would I just be looking to executerados - p .rgw.buckets.index rm .dir.default.5689810.107Is the differing marker/bucket_id in the other buckets that was found also an indicator? As I say, there's a good number of these, here's some additional examples, though these aren't necessarily reporting as large omap objects:"BUCKET1", "default.281853840.479", "default.105206134.5","BUCKET2", "default.364663174.1", "default.349712129.3674",Checking these other buckets, they are exhibiting the same sort of symptoms as the first (multiple instances of radosgw-admin metadata get showing what seem to be multiple resharding processes being run, with different mtimes recorded).ThanksChrisOn Thu, 4 Oct 2018 at 16:21 Konstantin Shalygin <k0ste@xxxxxxxx> wrote:
Hi, Ceph version: Luminous 12.2.7 Following upgrading to Luminous from Jewel we have been stuck with a cluster in HEALTH_WARN state that is complaining about large omap objects. These all seem to be located in our .rgw.buckets.index pool. We've disabled auto resharding on bucket indexes due to seeming looping issues after our upgrade. We've reduced the number reported of reported large omap objects by initially increasing the following value: ~# ceph daemon mon.ceph-mon-1 config get osd_deep_scrub_large_omap_object_value_sum_threshold { "osd_deep_scrub_large_omap_object_value_sum_threshold": "2147483648" } However we're still getting a warning about a single large OMAP object, however I don't believe this is related to an unsharded index - here's the log entry: 2018-10-01 13:46:24.427213 osd.477 osd.477 172.26.216.6:6804/2311858 8482 : cluster [WRN] Large omap object found. Object: 15:333d5ad7:::.dir.default.5689810.107:head Key count: 17467251 Size (bytes): 4458647149 The object in the logs is the "marker" object, rather than the bucket_id - I've put some details regarding the bucket here: https://pastebin.com/hW53kTxL The bucket limit check shows that the index is sharded, so I think this might be related to versioning, although I was unable to get confirmation that the bucket in question has versioning enabled through the aws cli(snipped debug output below) 2018-10-02 15:11:17,530 - MainThread - botocore.parsers - DEBUG - Response headers: {'date': 'Tue, 02 Oct 2018 14:11:17 GMT', 'content-length': '137', 'x-amz-request-id': 'tx0000000000000020e3b15-005bb37c85-15870fe0-default', 'content-type': 'application/xml'} 2018-10-02 15:11:17,530 - MainThread - botocore.parsers - DEBUG - Response body: <?xml version="1.0" encoding="UTF-8"?><VersioningConfiguration xmlns=" http://s3.amazonaws.com/doc/2006-03-01/"></VersioningConfiguration> After dumping the contents of large omap object mentioned above into a file it does seem to be a simple listing of the bucket contents, potentially an old index: ~# wc -l omap_keys 17467251 omap_keys This is approximately 5 million below the currently reported number of objects in the bucket. When running the commands listed here: http://tracker.ceph.com/issues/34307#note-1 The problematic bucket is listed in the output (along with 72 other buckets): "CLIENTBUCKET", "default.294495648.690", "default.5689810.107" As this tests for bucket_id and marker fields not matching to print out the information, is the implication here that both of these should match in order to fully migrate to the new sharded index? I was able to do a "metadata get" using what appears to be the old index object ID, which seems to support this (there's a "new_bucket_instance_id" field, containing a newer "bucket_id" and reshard_status is 2, which seems to suggest it has completed). I am able to take the "new_bucket_instance_id" and get additional metadata about the bucket, each time I do this I get a slightly newer "new_bucket_instance_id", until it stops suggesting updated indexes. It's probably worth pointing out that when going through this process the final "bucket_id" doesn't match the one that I currently get when running 'radosgw-admin bucket stats --bucket "CLIENTBUCKET"', even though it also suggests that no further resharding has been done as "reshard_status" = 0 and "new_bucket_instance_id" is blank. The output is available to view here: https://pastebin.com/g1TJfKLU It would be useful if anyone can offer some clarification on how to proceed from this situation, identifying and removing any old/stale indexes from the index pool (if that is the case), as I've not been able to spot anything in the archives. If there's any further information that is needed for additional context please let me know.
Usually, when you bucket is automatically resharded in some case old big index is not deleted - this is your large omap object.
This index is safe to delete. Also look at [1].
k
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