stats: warn for using id with custom router

CRUD stats are separated by space name. If space id is passed instead of
name (only `crud.len` allows this), space name is resolved with net_box
schema. Since, after resolving #44, non-default vshard routers and
Cartridge vshard groups are supported, to resolve the name we must know
what vshard router should be used. Since using space id for `crud.len`
is deprecated now, we won't support name resolve for operations with
custom router statistics. Instead of this, a warning will be logged.
`crud.len` statistics will be signed by space name or space id casted to
string depending on is there a default router with space schema or not.

Follows up #44, part of #255

crud/len.lua

@@ -52,6 +52,11 @@ function len.call(space_name, opts)
     if type(space_name) == 'number' then
         log.warn('Using space id in crud.len is deprecated and will be removed in future releases.' ..
                  'Please, use space name instead.')
+
+        if opts.vshard_router ~= nil then
+            log.warn('Using space id in crud.len and custom vshard_router is not supported by statistics.' ..
+                     'Space labels may be inconsistent.')
+        end
     end
 
     local vshard_router, err = utils.get_vshard_router_instance(opts.vshard_router)

crud/stats/init.lua

@@ -250,6 +250,7 @@ function stats.get(space_name)
 end
 
 local function resolve_space_name(space_id)
+    -- Resolving name with custom vshard router is not supported.
     local vshard_router = vshard.router.static
 
     if vshard_router == nil then

test/entrypoint/srv_vshard_custom.lua

@@ -24,6 +24,7 @@ package.preload['customers-storage'] = function()
                     },
                     if_not_exists = true,
                     engine = engine,
+                    id = 542,
                 })
 
                 customers_space:create_index('pk', {

test/integration/vshard_custom_test.lua

@@ -1,6 +1,7 @@
 local fio = require('fio')
 
 local t = require('luatest')
+local luatest_capture = require('luatest.capture')
 
 local helpers = require('test.helper')
 
@@ -1629,3 +1630,31 @@ pgroup.test_call_upsert_object_many_wrong_option = function(g)
     t.assert_str_contains(errs[1].err,
                           "Invalid opts.vshard_router table value, a vshard router instance has been expected")
 end
+
+pgroup.before_test('test_call_len_by_space_id_with_stats', function(g)
+    g.router:eval('crud.cfg{stats = true}')
+end)
+
+pgroup.test_call_len_by_space_id_with_stats = function(g)
+    local capture = luatest_capture:new()
+    capture:enable()
+
+    local result, err = g:call_router_opts2('len', 542, {vshard_router = 'customers'})
+    t.assert_equals(err, nil)
+    t.assert_equals(result, 2)
+
+    local captured = helpers.fflush_main_server_stdout(g.cluster, capture)
+    capture:disable()
+
+    t.assert_str_contains(captured,
+                          "Using space id in crud.len and custom vshard_router is not supported by statistics.")
+
+    local result, err = g.router:call('crud.stats')
+    t.assert_equals(err, nil)
+    t.assert_type(result.spaces["542"], 'table')
+    t.assert_equals(result.spaces["542"]["len"]["ok"]["count"], 1)
+end
+
+pgroup.after_test('test_call_len_by_space_id_with_stats', function(g)
+    g.router:eval('crud.cfg{stats = false}')
+end)