rgw: Add option to configure backend store

Signed-off-by: Soumya Koduri <skoduri@redhat.com>

src/common/options/rgw.yaml.in

@@ -3229,3 +3229,11 @@ options:
   - rgw
   flags:
   - startup
+- name: rgw_backend_store
+  type: str
+  level: advanced
+  desc: Experimental Option to set backend store type
+  long_desc: defaults to rados. Other valid values are dbstore(experimental).
+  default: rados
+  services:
+  - rgw

src/rgw/rgw_main.cc

@@ -346,9 +346,18 @@ int radosgw_Main(int argc, const char **argv)
   }
   lsubdout(cct, rgw, 1) << "D3N datacache enabled: " << rgw_d3n_datacache_enabled << dendl;
 
+  std::string rgw_store = (!rgw_d3n_datacache_enabled) ? "rados" : "d3n";
+
+  const auto& config_store = g_conf().get_val<std::string>("rgw_backend_store");
+#ifdef WITH_RADOSGW_DBSTORE
+  if (config_store == "dbstore") {
+    rgw_store = "dbstore";
+  }
+#endif
+
   rgw::sal::Store* store =
     StoreManager::get_storage(&dp, g_ceph_context,
-				 (!rgw_d3n_datacache_enabled) ? "rados" : "d3n",
+				 rgw_store,
 				 g_conf()->rgw_enable_gc_threads,
 				 g_conf()->rgw_enable_lc_threads,
 				 g_conf()->rgw_enable_quota_threads,