rgw: Adding data cache and CDN capabilities

rgw: Adding data cache and CDN capabilities

This feature is meant to add data cache feature to the RGW.
It is using Nginx as a cache server.
This feature adds 2 new apis, Auth api and Cache api.

Some Performance tests using hsbench:
16K objs:

RGW direct access:
Mode: GET, Ops: 3001, MB/s: 46.89, Lat(ms): [ min: 30.4, avg: 33.2, 99%: 34.7, max: 35.2 ]
Nginx access (objs have not been cached)
Mode: GET, Ops: 1363, MB/s: 21.30, Lat(ms): [ min: 63.8, avg: 73.8, 99%: 78.1, max: 86.6 ]
Nginx access (objs have been cached)
Mode: GET, Ops: 2446, MB/s: 38.22, Lat(ms): [ min: 36.9, avg: 41.0, 99%: 43.9, max: 45.9 ]

512K objs:
RGW direct access:
Mode: GET, Ops: 1492, MB/s: 746.00 Lat(ms): [ min: 60.4, avg: 66.7, 99%: 73.5, max: 75.9 ]

Nginx access (objs have not been cached)
Mode: GET, Ops: 1382, MB/s: 691.00, Lat(ms): [ min: 64.5, avg: 72.1, 99%: 77.9, max: 82.8 ]

Nginx access (objs have been cached)
Mode: GET, Ops: 2947, MB/s: 1473.50, Lat(ms): [ min: 3.3, avg: 32.7, 99%: 62.2, max: 72.1 ]

2M objs:
RGW direct access:
Mode: GET, Ops: 613, MB/s: 1226.00, Lat(ms): [ min: 143.6, avg: 162.0, 99%: 180.2, max: 190.1 ]

Nginx access (objs have not been cached)
Mode: GET, Ops: 462, MB/s: 924.00, Lat(ms): [ min: 180.2, avg: 215.0, 99%: 243.2, max: 248.3 ]

Nginx access (objs have been cached)
Mode: GET, Ops: 1392, MB/s: 2784.00, Lat(ms): [ min: 3.0, avg: 5.3, 99%: 18.8, max: 30.2 ]

10M objs:
RGW direct access:
Mode: GET, Ops: 135, MB/s: 1350.00, Lat(ms): [ min: 191.1, avg: 265.8, 99%: 373.1, max: 382.8 ]

Nginx access (objs have not been cached)
Mode: GET, Ops: 120, MB/s: 1200.00, Lat(ms): [ min: 302.1, avg: 428.8, 99%: 561.2, max: 583.7 ]

Nginx access (objs have been cached)
Mode: GET, Ops: 281, MB/s: 2810.00, Lat(ms): [ min: 3.2, avg: 8.3, 99%: 16.9, max: 25.6 ]

gdal_translate 4GiB image gdal_translate -co NUM_THREADS=ALL_CPUS /vsis3/hello/sat.tif

Nginx (have not cached):
real 0m24.714s
user 0m8.692s
sys 0m10.360s

Nginx (have been cached):
real 0m21.070s
user 0m9.140s
sys 0m10.316s

RGW:
real 0m21.859s
user 0m8.850s
sys 0m10.386s

The results are showing that for objects larger than 512K the cache will increase the performance by twice or more.

For small objs, the overhead of sending the auth request will make the cache less efficient

The result for cached objects in the 10MB test can be explained by net limit of 25 Gb/s(it could reach more)

In Gdal (image decoder/encoder over s3 using range requests) the results were not that different because of Gdal single cpu encoding/decoding.
Gdal have been chosen because of the ability to check the smart cache of the nginx.
https://www.nginx.com/blog/smart-efficient-byte-range-caching-nginx/

Signed-off-by: Or Friedmann <ofriedma@redhat.com>
(cherry picked from commit 1bcd212fd260e8436a2fe8858068c3613b30caed)