storage: fix assertion failure in conn_manager

conn_manager_collect_idle_conns is used in order to close connections,
which have not been used by a storage for a period of time. Currently,
it has an assertion, which checks, that node never connects to self.

However, storage establishes connection to self, e.g. during
downloading of bucket states for rebalancer. As this is expected
behavior, this commit deletes this assertion.

Closes #446

NO_DOC=bugfix

test/storage-luatest/auto_master_2_2_2_test.lua

@@ -287,3 +287,36 @@ test_group.test_noactivity_timeout_for_auto_master = function(g)
         _G.bucket_gc_wait()
     end, {g.replica_1_a:replicaset_uuid(), bid1, bid2})
 end
+
+test_group.test_conn_manager_connect_self = function(g)
+    vtest.cluster_rebalancer_enable(g)
+    t.assert_equals(vtest.cluster_rebalancer_find(g), 'replica_1_a')
+
+    g.replica_1_a:exec(function(uuid)
+        -- Create connections using rebalancer
+        local rebalancer = ivshard.storage.internal.rebalancer_service
+        ivtest.service_wait_for_new_ok(rebalancer,
+            {on_yield = ivshard.storage.rebalancer_wakeup})
+
+        -- Assert, that connection to self is created.
+        local replicaset = ivshard.storage.internal.replicasets[uuid]
+        ilt.assert_not_equals(replicaset.master, nil)
+
+        local old_timeout = ivconst.REPLICA_NOACTIVITY_TIMEOUT
+        ivconst.REPLICA_NOACTIVITY_TIMEOUT = 0.01
+        ifiber.sleep(ivconst.REPLICA_NOACTIVITY_TIMEOUT)
+        local conn_manager = ivshard.storage.internal.conn_manager_service
+        ivtest.service_wait_for_new_ok(conn_manager, {on_yield = function()
+            ivshard.storage.internal.conn_manager_fiber:wakeup()
+        end})
+        ilt.assert_equals(replicaset.master, nil)
+        ivconst.REPLICA_NOACTIVITY_TIMEOUT = old_timeout
+    end, {g.replica_1_a:replicaset_uuid()})
+
+    -- Check, that assert not fails
+    local err_msg = 'conn_manager_f has been failed'
+    t.assert_equals(g.replica_1_a:grep_log(err_msg), nil)
+
+    -- Cleanup
+    vtest.cluster_rebalancer_disable(g)
+end

vshard/storage/init.lua

@@ -3659,7 +3659,6 @@ local function conn_manager_collect_idle_conns()
             if c and replica.activity_ts and
                replica.activity_ts + consts.REPLICA_NOACTIVITY_TIMEOUT < ts then
                 if replica == rs.master and rs.is_master_auto then
-                    assert(rs ~= M.this_replicaset)
                     rs.master = nil
                 end
                 replica.conn = nil