storage: introduce box_cfg_mode

Part of #428

@TarantoolBot document
Title: vshard: `box_cfg_mode` cfg option

The option can be specified at the root level and regulates, whether
vshard calls box.cfg, when vshard.storage is invoked.

When specified to 'auto' (default), vshard configures box.cfg on its
own. When specified to 'manual', it's user's responsibility to call
box.cfg prior to vshard's configuration

Author: Serpentian

test/storage-luatest/box_cfg_mode_test.lua

@@ -0,0 +1,62 @@
+local t = require('luatest')
+local vtest = require('test.luatest_helpers.vtest')
+
+local test_group = t.group()
+
+local cfg_template = {
+    sharding = {
+        {
+            replicas = {
+                replica_1_a = {master = true},
+            },
+        },
+        {
+            replicas = {
+                replica_2_a = {master = true},
+            },
+        },
+    },
+    bucket_count = 20,
+    box_cfg_mode = 'manual',
+}
+
+local global_cfg
+
+test_group.before_all(function(g)
+    global_cfg = vtest.config_new(cfg_template)
+    vtest.cluster_new(g, global_cfg)
+    vtest.cluster_bootstrap(g, global_cfg)
+    vtest.cluster_wait_vclock_all(g)
+    vtest.cluster_rebalancer_disable(g)
+end)
+
+test_group.after_all(function(g)
+    g.cluster:stop()
+end)
+
+test_group.test_storage_disabled_error = function(g)
+    g.replica_1_a:exec(function(cfg)
+        local old_box = box.cfg
+        box.cfg = function() end
+        ilt.assert_error_msg_contains('Box must be configured', function()
+            ivshard.storage.cfg(cfg, box.info.uuid)
+        end)
+        box.cfg = old_box
+    end, {global_cfg})
+end
+
+--
+-- vtest.cluster_new does exactly, what user should do,
+-- when using 'manual' box_cfg_mode: call box.cfg prior
+-- to executing vshard.storage.cfg. So, just some basic test.
+--
+test_group.test_storage_basic = function(g)
+    t.assert(g.replica_1_a:grep_log('Box configuration was skipped'))
+    g.replica_1_a:exec(function(uuid)
+        local bid = _G.get_first_bucket()
+        local ok, err = ivshard.storage.bucket_send(bid, uuid)
+        ilt.assert_equals(err, nil)
+        ilt.assert(ok)
+        _G.bucket_gc_wait()
+    end, {g.replica_2_a:replicaset_uuid()})
+end

test/unit-luatest/config_test.lua

@@ -279,4 +279,15 @@ g.test_enum = function()
         "Discovery mode must be enum {'on', 'off', 'once', nil}",
         vcfg.check, config)
     config.discovery_mode = nil
+
+    config.box_cfg_mode = nil
+    for _, v in pairs({'auto', 'manual'}) do
+        config.box_cfg_mode = v
+        t.assert(vcfg.check(config))
+    end
+    config.box_cfg_mode = 'bad'
+    t.assert_error_msg_content_equals(
+        "Box.cfg mode must be enum {'auto', 'manual', nil}",
+        vcfg.check, config)
+    config.box_cfg_mode = nil
 end

vshard/cfg.lua

@@ -419,6 +419,10 @@ local cfg_template = {
         name = 'Scheduler bucket move quota', type = 'non-negative number',
         is_optional = true, default = consts.DEFAULT_SCHED_MOVE_QUOTA
     },
+    box_cfg_mode = {
+        name = 'Box.cfg mode', type = 'enum', is_optional = true,
+        default = 'auto', enum = {'auto', 'manual'},
+    }
 }
 
 --

vshard/storage/init.lua

@@ -3883,7 +3883,13 @@ local function storage_cfg_xc(cfgctx)
         error('Error injection: cfg')
     end
 
-    if not cfgctx.is_reload then
+    if cfgctx.new_cfg.box_cfg_mode == 'manual' then
+        if type(box.cfg) == 'function' then
+            local msg = "Box must be configured, when box_cfg_mode is 'manual'"
+            error(lerror.vshard(lerror.code.STORAGE_IS_DISABLED, msg))
+        end
+        log.info("Box configuration was skipped")
+    elseif not cfgctx.is_reload then
         storage_cfg_master_prepare(cfgctx)
         storage_cfg_build_local_box_cfg(cfgctx)