feat: support single replica (#932)

XiaoMi · Oct 25, 2021 · 56d6144 · 56d6144
1 parent 4cce780
commit 56d6144
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Showing 3 changed files with 19 additions and 9 deletions.
diff --git a/src/client/replication_ddl_client.cpp b/src/client/replication_ddl_client.cpp
@@ -128,8 +128,8 @@ dsn::error_code replication_ddl_client::create_app(const std::string &app_name,
         return ERR_INVALID_PARAMETERS;
     }
 
-    if (replica_count < 2) {
-        std::cout << "create app " << app_name << " failed: replica_count should >= 2" << std::endl;
+    if (replica_count < 1) {
+        std::cout << "create app " << app_name << " failed: replica_count should >= 1" << std::endl;
         return ERR_INVALID_PARAMETERS;
     }
 

diff --git a/src/meta/greedy_load_balancer.cpp b/src/meta/greedy_load_balancer.cpp
@@ -47,6 +47,8 @@ DSN_DEFINE_uint32("meta_server",
                   "balance operation count per round for cluster balancer");
 DSN_TAG_VARIABLE(balance_op_count_per_round, FT_MUTABLE);
 
+DSN_DECLARE_uint64(min_live_node_count_for_unfreeze);
+
 uint32_t get_partition_count(const node_state &ns, cluster_balance_type type, int32_t app_id)
 {
     unsigned count = 0;
@@ -795,7 +797,8 @@ void greedy_load_balancer::shortest_path(std::vector<bool> &visit,
 bool greedy_load_balancer::primary_balancer_per_app(const std::shared_ptr<app_state> &app,
                                                     bool only_move_primary)
 {
-    dassert(t_alive_nodes > 2, "too few alive nodes will lead to freeze");
+    dassert(t_alive_nodes >= FLAGS_min_live_node_count_for_unfreeze,
+            "too few alive nodes will lead to freeze");
     ddebug("primary balancer for app(%s:%d)", app->app_name.c_str(), app->app_id);
 
     const node_mapper &nodes = *(t_global_view->nodes);
@@ -888,7 +891,8 @@ bool greedy_load_balancer::all_replica_infos_collected(const node_state &ns)
 
 void greedy_load_balancer::greedy_balancer(const bool balance_checker)
 {
-    dassert(t_alive_nodes > 2, "too few nodes will be freezed");
+    dassert(t_alive_nodes >= FLAGS_min_live_node_count_for_unfreeze,
+            "too few nodes will be freezed");
     number_nodes(*t_global_view->nodes);
 
     for (auto &kv : *(t_global_view->nodes)) {

diff --git a/src/meta/meta_options.cpp b/src/meta/meta_options.cpp
@@ -34,9 +34,19 @@
  */
 #include "meta_options.h"
 
+#include <dsn/utility/flags.h>
+
 namespace dsn {
 namespace replication {
 
+DSN_DEFINE_uint64("meta_server",
+                  min_live_node_count_for_unfreeze,
+                  3,
+                  "minimum live node count without which the state is freezed");
+DSN_TAG_VARIABLE(min_live_node_count_for_unfreeze, FT_MUTABLE);
+DSN_DEFINE_validator(min_live_node_count_for_unfreeze,
+                     [](uint64_t min_live_node_count) -> bool { return min_live_node_count > 0; });
+
 std::string meta_options::concat_path_unix_style(const std::string &prefix,
                                                  const std::string &postfix)
 {
@@ -72,11 +82,7 @@ void meta_options::initialize()
         "if live_node_count * 100 < total_node_count * node_live_percentage_threshold_for_update, "
         "then freeze the cluster; default is 65");
 
-    min_live_node_count_for_unfreeze =
-        dsn_config_get_value_uint64("meta_server",
-                                    "min_live_node_count_for_unfreeze",
-                                    3,
-                                    "minimum live node count without which the state is freezed");
+    min_live_node_count_for_unfreeze = FLAGS_min_live_node_count_for_unfreeze;
 
     meta_function_level_on_start = meta_function_level::fl_invalid;
     const char *level_str = dsn_config_get_value_string(