From 3e3224f0a248da67250892df10f2f92251424cd6 Mon Sep 17 00:00:00 2001
From: Andi <andi8647@gmail.com>
Date: Fri, 16 Feb 2024 12:41:15 +0100
Subject: [PATCH] Forbid having multiple mains in the cluster (#1727)
---
src/coordination/coordinator_instance.cpp | 4 ++++
.../register_main_replica_coordinator_status.hpp | 1 +
src/query/interpreter.cpp | 2 ++
.../single_coordinator.py | 15 +++++++++++++++
4 files changed, 22 insertions(+)
diff --git a/src/coordination/coordinator_instance.cpp b/src/coordination/coordinator_instance.cpp
index b8afbb6a3..1bbcf4f8f 100644
--- a/src/coordination/coordinator_instance.cpp
+++ b/src/coordination/coordinator_instance.cpp
@@ -206,6 +206,10 @@ auto CoordinatorInstance::SetReplicationInstanceToMain(std::string instance_name
-> SetInstanceToMainCoordinatorStatus {
auto lock = std::lock_guard{coord_instance_lock_};
+ if (std::ranges::any_of(repl_instances_, &ReplicationInstance::IsMain)) {
+ return SetInstanceToMainCoordinatorStatus::MAIN_ALREADY_EXISTS;
+ }
+
auto const is_new_main = [&instance_name](ReplicationInstance const &instance) {
return instance.InstanceName() == instance_name;
};
diff --git a/src/coordination/include/coordination/register_main_replica_coordinator_status.hpp b/src/coordination/include/coordination/register_main_replica_coordinator_status.hpp
index 5fcb93921..3aa7e3ca1 100644
--- a/src/coordination/include/coordination/register_main_replica_coordinator_status.hpp
+++ b/src/coordination/include/coordination/register_main_replica_coordinator_status.hpp
@@ -39,6 +39,7 @@ enum class UnregisterInstanceCoordinatorStatus : uint8_t {
enum class SetInstanceToMainCoordinatorStatus : uint8_t {
NO_INSTANCE_WITH_NAME,
+ MAIN_ALREADY_EXISTS,
NOT_COORDINATOR,
SUCCESS,
COULD_NOT_PROMOTE_TO_MAIN,
diff --git a/src/query/interpreter.cpp b/src/query/interpreter.cpp
index f0fed2357..c7ccbb1ef 100644
--- a/src/query/interpreter.cpp
+++ b/src/query/interpreter.cpp
@@ -563,6 +563,8 @@ class CoordQueryHandler final : public query::CoordinatorQueryHandler {
using enum memgraph::coordination::SetInstanceToMainCoordinatorStatus;
case NO_INSTANCE_WITH_NAME:
throw QueryRuntimeException("No instance with such name!");
+ case MAIN_ALREADY_EXISTS:
+ throw QueryRuntimeException("Couldn't set instance to main since there is already a main instance in cluster!");
case NOT_COORDINATOR:
throw QueryRuntimeException("SET INSTANCE TO MAIN query can only be run on a coordinator!");
case COULD_NOT_PROMOTE_TO_MAIN:
diff --git a/tests/e2e/high_availability_experimental/single_coordinator.py b/tests/e2e/high_availability_experimental/single_coordinator.py
index d1df05b4f..8e620e7e4 100644
--- a/tests/e2e/high_availability_experimental/single_coordinator.py
+++ b/tests/e2e/high_availability_experimental/single_coordinator.py
@@ -515,5 +515,20 @@ def test_automatic_failover_main_back_as_main():
mg_sleep_and_assert([("main",)], retrieve_data_show_repl_role_instance3)
+def test_disable_multiple_mains():
+ safe_execute(shutil.rmtree, TEMP_DIR)
+ interactive_mg_runner.start_all(MEMGRAPH_INSTANCES_DESCRIPTION)
+
+ coord_cursor = connect(host="localhost", port=7690).cursor()
+
+ try:
+ execute_and_fetch_all(
+ coord_cursor,
+ "SET INSTANCE instance_1 TO MAIN;",
+ )
+ except Exception as e:
+ assert str(e) == "Couldn't set instance to main since there is already a main instance in cluster!"
+
+
if __name__ == "__main__":
sys.exit(pytest.main([__file__, "-rA"]))