Hey all,
I've just recently upgraded some of my larger rgw clusters to latest luminous and now I'm getting a lot of warnings about large omap objects. Most of them were on the indices and I've taken care of them by sharding where appropriate. However on two of my clusters I have a large object in the rgw log pool.
ceph health detail
HEALTH_WARN 1 large omap objects
LARGE_OMAP_OBJECTS 1 large omap objects
1 large objects found in pool '.us-phx2.log'
Search the cluster log for 'Large omap object found' for more details.
2019-06-11 10:50:04.583354 7f8d2b737700 0 log_channel(cluster) log [WRN] : Large omap object found. Object: 51:b9a904f6:::data_log.27:head Key count: 15903755 Size (bytes): 2305116273
I'm not sure what to make of this. I don't see much chatter on the mailing lists about the log pool, other than a thread about swift lifecycles, which I dont use. The log pool is pretty large, making it difficult to poke around in there:
.us-phx2.log 51 118GiB 0.03 384TiB 12782413
That said i did a little poking around and it looks like a mix of these data_log object and some delete hints, but mostly a lot of objects starting with dates that point to different s3 pools. The object referenced in the osd log has 15912300 omap keys, and spot checking it, it looks like it's mostly referencing a pool we use with out dns resolver. We have a dns service that checks rgw endpoint health by uploading and deleting an object every few minutes to check health, and adds/removes endpoints from the A record as indicated.
So I guess I've got a few questions:
1) what is the nature of the data in the data_log.* objects in the log pool? Is it safe to remove or is it more like a binlog that needs to be intact from the beginning of time?
2) with the log pool in general, beyond the individual objects omap sizes, is there any concern about size? If so, is there a way to force it to truncate? I see some log commands in radosgw-admin, but documentation is light.
Thanks,
Aaron
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