Exposing Leader to upper layer

SM needs to return leader in both response of some API call
as well as PGStat report.

This helps client(of SM)  to know up-to-date leader and send
requests to leader.

Signed-off-by: Xiaoxi Chen <[email protected]>

conanfile.py

@@ -8,7 +8,7 @@
 
 class NuRaftMesgConan(ConanFile):
     name = "nuraft_mesg"
-    version = "2.1.2"
+    version = "2.2.2"
 
     homepage = "https://github.com/eBay/nuraft_mesg"
     description = "A gRPC service for NuRAFT"

include/nuraft_mesg/mesg_state_mgr.hpp

@@ -36,6 +36,7 @@ class repl_service_ctx {
     // we do not own this pointer. Use this only if the life cycle of the pointer is well known
     nuraft::raft_server* _server;
     bool is_raft_leader() const;
+    const std::string& raft_leader_id() const;
 
     // return a list of replica configs for the peers of the raft group
     void get_cluster_config(std::list< replica_config >& cluster_config) const;

src/lib/repl_service_ctx.cpp

@@ -64,6 +64,18 @@ repl_service_ctx::repl_service_ctx(nuraft::raft_server* server) : _server(server
 
 bool repl_service_ctx::is_raft_leader() const { return _server->is_leader(); }
 
+const std::string& repl_service_ctx::raft_leader_id() const {
+    // when adding member to raft,  the id recorded in raft is a hash
+    // of passed-in id (new_id in add_member()), the new_id was stored
+    // in endpoint field.
+    static std::string const empty;
+    if (!_server) return empty;
+    auto const leader = _server->get_leader();
+    if (leader == -1) return empty;
+    auto const& srv_config = _server->get_srv_config(leader);
+    return (srv_config) ? srv_config->get_endpoint() : empty;
+}
+
 void repl_service_ctx::get_cluster_config(std::list< replica_config >& cluster_config) const {
     auto const& srv_configs = _server->get_config()->get_servers();
     for (auto const& srv_config : srv_configs) {

src/tests/test_fixture.ipp

@@ -198,6 +198,10 @@ protected:
         auto const dest_cfg = nuraft::srv_config(to_server_id(app_1_->id_), to_string(app_1_->id_));
         EXPECT_TRUE(factory->add_server(to_server_id(app_3_->id_), app_3_->id_, dest_cfg).get());
         std::this_thread::sleep_for(std::chrono::seconds(1));
+
+        // Check leader
+        EXPECT_TRUE(app_1_->state_mgr_map_[group_id_]->get_repl_context()->is_raft_leader());
+        EXPECT_TRUE(app_1_->state_mgr_map_[group_id_]->get_repl_context()->raft_leader_id() == app_1_->id_);
     }
 };