fix(test): fix flaky test on cluster with replication

tarantool uses async replication by default, and it is possible to try selecting from a replica that does not have the space or the data yet, which can cause flaky tests
now, we configure storage replicaset and enable sync replication for spaces to work with
Closes #369

sbroad-cartridge/test_app/test/helper/cluster_async_replication.lua → sbroad-cartridge/test_app/test/helper/cluster_sync_replication.lua

@@ -2,6 +2,7 @@
 -- Add common configuration here.
 
 local fio = require('fio')
+local fiber = require("fiber")
 local t = require('luatest')
 local cartridge_helpers = require('cartridge.test-helpers')
 local config_handler = require('test.helper.config_handler')
@@ -56,6 +57,39 @@ helper.start_test_cluster = function (cfg)
     })
 
     helper.cluster:start()
+
+    local storage11 = helper.cluster:server("storage-1-1").net_box
+    local storage12 = helper.cluster:server("storage-1-2").net_box
+
+    -- storage master
+    storage11:eval("box.cfg{election_mode='candidate'}")
+    -- storage replica
+    storage12:eval("box.cfg{election_mode='voter'}")
+
+    local WAITING_TIMEOUT = 20
+    local fiber_sleep = 0.01
+    local wait_start = fiber.clock()
+
+    local s11_ro = storage11:eval("return box.info.ro")
+    local s12_ro = storage12:eval("return box.info.ro")
+
+    -- wait until new replicaset configuration finishes
+    -- when it happens, master will be readable/writable while replica will be only readable
+    while s11_ro do
+        fiber.sleep(fiber_sleep)
+        s11_ro = storage11:eval("return box.info.ro")
+        s12_ro = storage12:eval("return box.info.ro")
+
+        local current_time = fiber.clock()
+        if current_time > wait_start + WAITING_TIMEOUT then
+            t.fail("timeout exceed waiting replication")
+        end
+    end
+    t.assert_equals({s11_ro, s12_ro}, {false, true})
+
+    -- replicaset has master and one replica
+    storage11:eval("box.cfg{replication_synchro_quorum=2}")
+
     helper.cluster:upload_config(cfg)
 end
 

sbroad-cartridge/test_app/test/integration/sql_cache_test.lua

 local t = require('luatest')
 local g = t.group('configuration.sql_cache')
 
-local helper = require('test.helper.cluster_async_replication')
+local helper = require('test.helper.cluster_sync_replication')
 local cluster = nil
 
 g.before_all(
@@ -10,9 +10,10 @@ g.before_all(
         cluster = helper.cluster
 
         local storage1 = cluster:server("storage-1-1").net_box
-        storage1:call("box.execute", { [[truncate table "space_for_breake_cache"]] })
-
         local storage2 = cluster:server("storage-2-1").net_box
+
+        storage1:call("box.space.space_for_breake_cache:alter", { {is_sync = true}})
+        storage1:call("box.execute", { [[truncate table "space_for_breake_cache"]] })
         storage2:call("box.execute", { [[truncate table "space_for_breake_cache"]] })
     end
 )