router: allow calling info when disabled

A router may be marked as disabled, which previously made it difficult
to obtain status information from the component.

This patch allows calling vshard.router.info even when the component
is disabled. The function now also returns a new boolean field
is_enabled indicating whether the component is currently enabled.

Follow-up #565

@TarantoolBot document
Title: vshard: router.info behavior change

vshard.router.info()

This function can now be called even when the router is disabled.

It now also returns a new boolean field is_enabled indicating
whether the component is currently enabled.

Author: kamenkremen

test/failover/cluster_changes.result

@@ -127,6 +127,7 @@ info
     available_rw: 0
   identification_mode: uuid_as_key
   status: 1
+  is_enabled: true
   alerts:
   - ['UNKNOWN_BUCKETS', '3000 buckets are not discovered']
 ...
@@ -278,6 +279,7 @@ info
     available_rw: 0
   identification_mode: uuid_as_key
   status: 3
+  is_enabled: true
   alerts:
   - ['MISSING_MASTER', 'Master is not configured for replicaset 739fe4fb-2850-4cde-9637-10150724c5eb']
   - ['MISSING_MASTER', 'Master is not configured for replicaset 832bbba0-9699-4aa1-907d-c7c7af61f5c9']
@@ -384,6 +386,7 @@ info
     available_rw: 0
   identification_mode: uuid_as_key
   status: 1
+  is_enabled: true
   alerts:
   - ['UNKNOWN_BUCKETS', '3000 buckets are not discovered']
 ...

test/rebalancer/restart_during_rebalancing.result

@@ -285,6 +285,7 @@ info
     available_rw: 200
   identification_mode: uuid_as_key
   status: 0
+  is_enabled: true
   alerts: []
 ...
 util.stop_loading()

test/router-luatest/router_2_2_test.lua

@@ -1265,3 +1265,37 @@ g.test_log_ratelimiter_is_dropped_on_disable_of_the_service = function(g)
         _G.ratelimit = nil
     end, {name})
 end
+
+g.test_info_disable_consistency = function(g)
+    local router = vtest.router_new(g, 'router_1')
+    router:exec(function(cfg)
+        ivtest.clear_test_cfg_options(cfg)
+        -- Do not allow router's configuration to complete.
+        _G.ivshard.router.internal.errinj.ERRINJ_CFG_DELAY = true
+        local fiber_cfg = ifiber.create(ivshard.router.cfg, cfg)
+        fiber_cfg:set_joinable(true)
+        local routers = ivshard.router.internal.routers
+        local _, err = pcall(routers._static_router.info,
+                             routers._static_router)
+        ilt.assert_not_equals(err, nil)
+        ilt.assert_str_contains(err.message, 'router is not configured')
+
+        -- Unblock router's configuration and wait until it's finished.
+        _G.ivshard.router.internal.errinj.ERRINJ_CFG_DELAY = false
+        fiber_cfg:join()
+        local res = ivshard.router:info()
+        ilt.assert_not_equals(res, nil)
+        ilt.assert(res.is_enabled)
+
+        ivshard.router:disable()
+        res = ivshard.router:info()
+        ilt.assert_not_equals(res, nil)
+        ilt.assert_not(res.is_enabled)
+
+        ivshard.router:enable()
+        res = ivshard.router:info()
+        t.assert_not_equals(res, nil)
+        t.assert(res.is_enabled)
+    end, {global_cfg})
+    vtest.drop_instance(g, router)
+end

test/router/reconnect_to_master.result

@@ -149,6 +149,7 @@ vshard.router.info()
     available_rw: 0
   identification_mode: uuid_as_key
   status: 2
+  is_enabled: true
   alerts:
   - ['UNREACHABLE_MASTER', 'Master of replicaset cbf06940-0790-498b-948d-042b62cf3d29
       is unreachable: disconnected']

test/router/router.result

@@ -220,6 +220,7 @@ vshard.router.info()
     available_rw: 1
   identification_mode: uuid_as_key
   status: 1
+  is_enabled: true
   alerts:
   - ['UNKNOWN_BUCKETS', '2999 buckets are not discovered']
 ...
@@ -1076,6 +1077,7 @@ info
     available_rw: 3000
   identification_mode: uuid_as_key
   status: 0
+  is_enabled: true
   alerts: []
 ...
 -- Remove replica and master connections to trigger alert

vshard/router/init.lua

@@ -1546,6 +1546,7 @@ local function router_info(router, opts)
                 router.discovery_service:info(),
         }
     end
+    state.is_enabled = router.is_enabled
     return state
 end
 
@@ -1661,31 +1662,32 @@ end
 -- Public API protection
 --------------------------------------------------------------------------------
 
-local function router_api_call_safe(func, router, ...)
+local function router_api_call_safe(func, router, _opts, ...)
     return func(router, ...)
 end
 
 --
 -- Unsafe proxy is loaded with protections. But it is used rarely and only in
 -- the beginning of instance's lifetime.
 --
-local function router_api_call_unsafe(func, router, ...)
+local function router_api_call_unsafe(func, router, opts, ...)
     -- Router can be started on instance with unconfigured box.cfg.
     if not router.is_configured then
         local msg = 'router is not configured'
         return error(lerror.vshard(lerror.code.ROUTER_IS_DISABLED, msg))
     end
-    if not router.is_enabled then
+    local is_disabled_skip = opts and opts.is_disabled_skip
+    if not router.is_enabled and not is_disabled_skip then
         local msg = 'router is disabled explicitly'
         return error(lerror.vshard(lerror.code.ROUTER_IS_DISABLED, msg))
     end
     router.api_call_cache = router_api_call_safe
     return func(router, ...)
 end
 
-local function router_make_api(func)
+local function router_make_api(func, opts)
     return function(router, ...)
-        return router.api_call_cache(func, router, ...)
+        return router.api_call_cache(func, router, opts, ...)
     end
 end
 
@@ -1709,7 +1711,7 @@ end
 local router_mt = {
     __index = {
         cfg = function(router, cfg) return router_cfg_fiber_safe(router, cfg, false) end,
-        info = router_make_api(router_info),
+        info = router_make_api(router_info, {is_disabled_skip = true}),
         buckets_info = router_make_api(router_buckets_info),
         call = router_make_api(router_call),
         callro = router_make_api(router_callro),