[TNTP-2109] Simplify rebalance metrics

Author: ita-sammann

crud.lua

@@ -175,7 +175,6 @@ crud.rebalance.router_cache_last_clear_ts = rebalance.router_api.cache_last_clea
 
 function crud.init_router()
     rawset(_G, 'crud', crud)
-    rebalance.metrics.enable_router_metrics()
 end
 
 function crud.stop_router()

crud/common/rebalance.lua

@@ -105,8 +105,6 @@ local function create_trigger()
 end
 
 function rebalance.init()
-    rebalance.metrics.enable_storage_metrics()
-
     local stored_safe_mode
     if not box.info.ro then
         if box.space[SAFE_MODE_SPACE] == nil then
@@ -142,7 +140,6 @@ function rebalance.safe_mode_disable()
 end
 
 --- Rebalance storage API
-
 rebalance.storage_api = {
     rebalance_safe_mode_status = rebalance.safe_mode_status,
     rebalance_safe_mode_enable = rebalance.safe_mode_enable,
@@ -153,41 +150,34 @@ rebalance.storage_api = {
 rebalance.router_api = {}
 
 function rebalance.router_api.cache_clear()
+    local router = utils.get_vshard_router_instance()
+    if router == nil then
+        log.warn("Router is not initialized yet")
+        return
+    end
     rebalance._router_cache_last_clear_ts = fiber.time()
-    return utils.get_vshard_router_instance():_route_map_clear()
+    return router:_route_map_clear()
 end
 
 function rebalance.router_api.cache_length()
-    return utils.get_vshard_router_instance().known_bucket_count
+    local router = utils.get_vshard_router_instance()
+    if router == nil then
+        log.warn("Router is not initialized yet")
+        return
+    end
+    return router.known_bucket_count
 end
 
 function rebalance.router_api.cache_last_clear_ts()
     return rebalance._router_cache_last_clear_ts
 end
 
 --- Rebalance related metrics
-rebalance.metrics = {}
-
-function rebalance.metrics.enable_storage_metrics()
-    if not has_metrics_module then
-        return
-    end
-
+if has_metrics_module then
     local safe_mode_enabled_gauge = metrics.gauge(
             'tnt_crud_storage_safe_mode_enabled',
             "is safe mode enabled on this storage instance"
     )
-
-    metrics.register_callback(function()
-        safe_mode_enabled_gauge:set(rebalance.safe_mode_status() and 1 or 0)
-    end)
-end
-
-function rebalance.metrics.enable_router_metrics()
-    if not has_metrics_module then
-        return
-    end
-
     local router_cache_length_gauge = metrics.gauge(
             'tnt_crud_router_cache_length',
             "number of bucket routes in vshard router cache"
@@ -198,6 +188,7 @@ function rebalance.metrics.enable_router_metrics()
     )
 
     metrics.register_callback(function()
+        safe_mode_enabled_gauge:set(rebalance.safe_mode_status() and 1 or 0)
         router_cache_length_gauge:set(rebalance.router_api.cache_length())
         router_cache_last_clear_ts_gauge:set(rebalance.router_api.cache_last_clear_ts())
     end)