Ceph: After upgrade to RHCS 5.3, bucket listings do not work and bucket stats have gone to zero, bucket_index_max_shards = 0

Issue

After upgrading to RHCS 5.3, bucket listings do not work and bucket stats have gone to zero, bucket_index_max_shards = 0

For a correct understanding, the variable bucket_index_max_shards does not indicate the maximum number of shards for the bucket index. It actually indicates the beginning (initial) number of shards a new bucket's index will receive.

Check the value of bucket_index_max_shards:

# radosgw-admin zonegroup get | grep bucket_index_max_shards
            "bucket_index_max_shards": 0,

To check multiple zones, run command multiple times, specifying each zone:

# radosgw-admin zonegroup get --rgw-zone={name of zone} | grep bucket_index_max_shards
            "bucket_index_max_shards": 0,

Beginning with RHCS 5.3, resharding a bucket when bucket_index_max_shards is 0 will result in the bucket's metadata being lost. Despite losing the bucket's metadata, the actual data is intact.