raft: make replicate_sync truly blocking

Signed-off-by: Michael Maurer <[email protected]>

Author: maurermi

src/util/raft/node.cpp

@@ -5,6 +5,8 @@
 
 #include "node.hpp"
 
+#include <future>
+
 namespace cbdc::raft {
     node::node(int node_id,
                std::vector<network::endpoint_t> raft_endpoints,
@@ -99,11 +101,26 @@ namespace cbdc::raft {
     auto node::replicate_sync(const nuraft::ptr<nuraft::buffer>& new_log) const
         -> std::optional<nuraft::ptr<nuraft::buffer>> {
         auto ret = m_raft_instance->append_entries({new_log});
-        if(!ret->get_accepted()
-           || ret->get_result_code() != nuraft::cmd_result_code::OK) {
+        if(!ret->get_accepted()) {
+            return std::nullopt;
+        }
+        auto result_code = nuraft::cmd_result_code::RESULT_NOT_EXIST_YET;
+        auto blocking_promise = std::promise<void>();
+        auto blocking_future = blocking_promise.get_future();
+        ret->when_ready([&result_code,
+                         &blocking_promise](raft::result_type& r,
+                                            nuraft::ptr<std::exception>& err) {
+            if(err) {
+                result_code = nuraft::cmd_result_code::FAILED;
+            } else {
+                result_code = r.get_result_code();
+            }
+            blocking_promise.set_value();
+        });
+        blocking_future.wait();
+        if(result_code != nuraft::cmd_result_code::OK) {
             return std::nullopt;
         }
-
         return ret->get();
     }
 

tests/unit/raft_test.cpp

@@ -173,6 +173,10 @@ class raft_test : public ::testing::Test {
         auto new_log
             = cbdc::make_buffer<uint64_t, nuraft::ptr<nuraft::buffer>>(1);
 
+        auto res = nodes[0]->replicate_sync(new_log);
+        ASSERT_TRUE(res.has_value());
+        ASSERT_EQ(nodes[0]->last_log_idx(), 2UL);
+
         cbdc::raft::callback_type result_fn = nullptr;
         auto result_done = std::atomic<bool>(false);
         if(!blocking) {
@@ -190,14 +194,7 @@ class raft_test : public ::testing::Test {
         while(!result_done) {
             std::this_thread::sleep_for(std::chrono::milliseconds(250));
         }
-        ASSERT_EQ(nodes[0]->last_log_idx(), 2UL);
-
-        if(blocking) {
-            // Replicate sync will only return a value in the blocking context
-            auto res = nodes[0]->replicate_sync(new_log);
-            ASSERT_TRUE(res.has_value());
-            ASSERT_EQ(nodes[0]->last_log_idx(), 3UL);
-        }
+        ASSERT_EQ(nodes[0]->last_log_idx(), 3UL);
 
         for(size_t i{0}; i < nodes.size(); i++) {
             ASSERT_EQ(nodes[i]->get_sm(), sms[i].get());