rgw: move compression config into zone placement

[cbodley]

This replaces the rgw_compression_type config option with an entry in the zone configuration, which can be set with the --compression= option to radosgw-admin zone create or zone modify.

Also adds some new documentation.

[cbodley]

the new doc can be viewed here: http://docs.ceph.com/docs/wip-rgw-zone-compression/radosgw/compression/

[cbodley]

@oritwas could you help review please?

[cbodley]

adding @yehudasa

[yehudasa]

lgtm

[yehudasa]

@cbodley actually, maybe we want to have this as part of the specific placement target config, and not globally per zone?

open question

[oritwas]

@cbodley , I think making it part of specific placement target config sounds useful.

[cbodley]

@cbodley actually, maybe we want to have this as part of the specific placement target config, and not globally per zone?

adding it to placement targets does make sense

i'd prefer not to require admins to edit their zone json to set these, so new radosgw-admin commands to add/remove/edit placement targets would be nice. and the placement target stuff is only documented under Regions: Set a Region in config-ref.rst - that stuff really needs to be updated to reflect the new multisite terminology (and probably moved into multisite.rst)

are these changes in scope for the kraken rc? or should the compression doc just say radosgw-admin zone get -> [edit json] -> zone set for now?

[cbodley]

• moved the compression_type field into RGWZonePlacementInfo
• added the --compression option to the radosgw-admin zone placement commands
• moved documentation into a separate pr at doc: add docs for rgw compression #12244
• marked [DNM] because this includes unmerged commits from radosgw-admin: more on placement configuration #12242

tested with a custom multisite cluster, with compression enabled thusly:

radosgw-admin zone placement modify --rgw-zone na-1 --placement-id=default-placement --compression=random

[cbodley]

rebased after merge of #12242 and removed [DNM] tag

[yehudasa]

lgtm