[tarantool-patches] [PATCH 1/3] box: make replication_sync_lag option dynamic

[Olga Arkhangelskaia]

In gh-3427 replication_sync_lag should be taken into account during
replication reconfiguration. In order to configure replication properly
this parameter is made dynamical and can be changed on demand.

@TarantoolBot document
Title: recation_sync_lag option can be set dynamically
recation_sync_lag now can be set at any time.
---
 src/box/box.cc            |  8 +++++++-
 src/box/box.h             |  1 +
 src/box/lua/cfg.cc        | 12 ++++++++++++
 src/box/lua/load_cfg.lua  |  2 ++
 test/box-tap/cfg.test.lua |  7 ++++++-
 5 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/src/box/box.cc b/src/box/box.cc
index 8d7454d1f..7155ad085 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -656,6 +656,12 @@ box_set_replication_connect_quorum(void)
 		replicaset_check_quorum();
 }
 
+void
+box_set_replication_sync_lag(void)
+{
+	replication_sync_lag = box_check_replication_sync_lag();
+}
+
 void
 box_bind(void)
 {
@@ -1747,7 +1753,7 @@ box_cfg_xc(void)
 	box_set_replication_timeout();
 	box_set_replication_connect_timeout();
 	box_set_replication_connect_quorum();
-	replication_sync_lag = box_check_replication_sync_lag();
+	box_set_replication_sync_lag();
 	xstream_create(&join_stream, apply_initial_join_row);
 	xstream_create(&subscribe_stream, apply_row);
 
diff --git a/src/box/box.h b/src/box/box.h
index 9dfb3fd2a..3090fdcdb 100644
--- a/src/box/box.h
+++ b/src/box/box.h
@@ -176,6 +176,7 @@ void box_set_vinyl_timeout(void);
 void box_set_replication_timeout(void);
 void box_set_replication_connect_timeout(void);
 void box_set_replication_connect_quorum(void);
+void box_set_replication_sync_lag(void);
 
 extern "C" {
 #endif /* defined(__cplusplus) */
diff --git a/src/box/lua/cfg.cc b/src/box/lua/cfg.cc
index 0ca150877..5442723b5 100644
--- a/src/box/lua/cfg.cc
+++ b/src/box/lua/cfg.cc
@@ -262,6 +262,17 @@ lbox_cfg_set_replication_connect_quorum(struct lua_State *L)
 	return 0;
 }
 
+static int
+lbox_cfg_set_replication_sync_lag(struct lua_State *L)
+{
+	try {
+		box_set_replication_sync_lag();
+	} catch (Exception *) {
+		luaT_error(L);
+	}
+	return 0;
+}
+
 void
 box_lua_cfg_init(struct lua_State *L)
 {
@@ -286,6 +297,7 @@ box_lua_cfg_init(struct lua_State *L)
 		{"cfg_set_replication_timeout", lbox_cfg_set_replication_timeout},
 		{"cfg_set_replication_connect_timeout", lbox_cfg_set_replication_connect_timeout},
 		{"cfg_set_replication_connect_quorum", lbox_cfg_set_replication_connect_quorum},
+		{"cfg_set_replication_sync_lag", lbox_cfg_set_replication_sync_lag},
 		{NULL, NULL}
 	};
 
diff --git a/src/box/lua/load_cfg.lua b/src/box/lua/load_cfg.lua
index 2a7142de6..f803d8987 100644
--- a/src/box/lua/load_cfg.lua
+++ b/src/box/lua/load_cfg.lua
@@ -199,6 +199,7 @@ local dynamic_cfg = {
     replication_timeout     = private.cfg_set_replication_timeout,
     replication_connect_timeout = private.cfg_set_replication_connect_timeout,
     replication_connect_quorum = private.cfg_set_replication_connect_quorum,
+    replication_sync_lag    = private.cfg_set_replication_sync_lag,
     instance_uuid           = function()
         if box.cfg.instance_uuid ~= box.info.uuid then
             box.error(box.error.CFG, 'instance_uuid',
@@ -220,6 +221,7 @@ local dynamic_cfg_skip_at_load = {
     replication_timeout     = true,
     replication_connect_timeout = true,
     replication_connect_quorum = true,
+    replication_sync_lag    = true,
     wal_dir_rescan_delay    = true,
     custom_proc_title       = true,
     force_recovery          = true,
diff --git a/test/box-tap/cfg.test.lua b/test/box-tap/cfg.test.lua
index 5e72004ca..d315346de 100755
--- a/test/box-tap/cfg.test.lua
+++ b/test/box-tap/cfg.test.lua
@@ -6,7 +6,7 @@ local socket = require('socket')
 local fio = require('fio')
 local uuid = require('uuid')
 local msgpack = require('msgpack')
-test:plan(90)
+test:plan(91)
 
 --------------------------------------------------------------------------------
 -- Invalid values
@@ -95,6 +95,11 @@ test:ok(status and result == 'table', 'configured box')
 
 invalid('log_level', 'unknown')
 
+lag = box.cfg.replication_sync_lag
+status, result = pcall(box.cfg, {replication_sync_lag = 1})
+test:ok(status, "dynamic replication_sync_lag")
+pcall(box.cfg, {repliction_sync_lag = lag})
+
 --------------------------------------------------------------------------------
 -- gh-534: Segmentation fault after two bad wal_mode settings
 --------------------------------------------------------------------------------
-- 
2.14.3 (Apple Git-98)