test: wait until cluster leaders are rw

Tarantool 3.0 instances start in ro mode. It is possible that masters
are not available for write requests right after test case has been
started.

Cartridge servers run only on Tarantool 1.x and 2.x, so they are
expected to work fine without additional changes: Cartridge helpers
checks are sophisticated enough.

Part of #412
Part of #415

test/helper.lua

@@ -116,7 +116,13 @@ function helpers.get_results_list(results_map)
     return results_list
 end
 
-function helpers.box_cfg()
+function helpers.box_cfg(opts)
+    opts = opts or {}
+
+    if opts.wait_rw == nil then
+        opts.wait_rw = true
+    end
+
     if type(box.cfg) ~= 'function' then
         return
     end
@@ -127,6 +133,13 @@ function helpers.box_cfg()
         wal_mode = 'none',
     })
     fio.rmtree(tempdir)
+
+    if opts.wait_rw then
+        t.helpers.retrying(
+            {timeout = 3, delay = 0.1},
+            t.assert_equals, box.info.ro, false
+        )
+    end
 end
 
 function helpers.insert_objects(g, space_name, objects)

test/integration/select_readview_test.lua

@@ -2308,6 +2308,8 @@ pgroup.test_stop_select = function(g)
     g.cluster:server('s2-master'):start()
 
     if g.params.backend == helpers.backend.VSHARD then
+        g.cluster:server('s2-master'):wait_for_rw()
+
         local bootstrap_key
         if type(g.params.backend_cfg) == 'table'
         and g.params.backend_cfg.identification_mode == 'name_as_key' then

test/unit/sharding_metadata_test.lua

@@ -24,25 +24,25 @@ g.before_each(function()
         {name = 'sharding_func_body', type = 'string', is_nullable = true},
     }
 
-    if type(box.cfg) ~= 'table' then
-        helpers.box_cfg()
-    end
+    helpers.box_cfg()
 
     -- Create a space _ddl_sharding_key with a tuple that
     -- contains a space name and it's sharding key.
     box.schema.space.create('_ddl_sharding_key', {
         format = sharding_key_format,
+        if_not_exists = true,
     })
-    box.space._ddl_sharding_key:create_index('pk')
+    box.space._ddl_sharding_key:create_index('pk', {if_not_exists = true})
 
     -- Create a space _ddl_sharding_func with a tuple that
     -- contains a space name and it's sharding func name/body.
     box.schema.space.create('_ddl_sharding_func', {
         format = sharding_func_format,
+        if_not_exists = true,
     })
-    box.space._ddl_sharding_func:create_index('pk')
+    box.space._ddl_sharding_func:create_index('pk', {if_not_exists = true})
 
-    box.schema.space.create('fetch_on_storage')
+    box.schema.space.create('fetch_on_storage', {if_not_exists = true})
 end)
 
 -- Since Tarantool 3.0 triggers still live after a space drop. To properly

test/vshard_helpers/server.lua

@@ -114,6 +114,16 @@ function Server:wait_for_readiness()
     end)
 end
 
+function Server:wait_for_rw()
+    return wait_cond('rw', self, function()
+        local ok, is_ready = pcall(function()
+            self:connect_net_box()
+            return self.net_box:eval('return box.info.ro') == false
+        end)
+        return ok and is_ready
+    end)
+end
+
 function Server:wait_election_leader()
     -- Include read-only property too because if an instance is a leader, it
     -- does not mean it finished the synchro queue ownership transition. It is

test/vshard_helpers/vtest.lua

@@ -495,6 +495,7 @@ local function cluster_new(g, cfg)
 
     for _, master in pairs(masters) do
         master:wait_for_readiness()
+        master:wait_for_rw()
         master:exec(function(cfg)
             -- Logged in as guest with 'super' access rights. Yet 'super' is not
             -- enough to grant 'replication' privilege. The simplest way - login