subscriber_statistics_collectors_ should be protected by mutex. (#2592)

* subscriber_statistics_collectors_ should be protected by mutex.

Signed-off-by: Tomoya Fujita <Tomoya.Fujita@sony.com>

* reduce mutex lock scope.

Signed-off-by: Tomoya Fujita <Tomoya.Fujita@sony.com>

---------

Signed-off-by: Tomoya Fujita <Tomoya.Fujita@sony.com>

Author: fujitatomoya

rclcpp/include/rclcpp/topic_statistics/subscription_topic_statistics.hpp

@@ -172,12 +172,11 @@ class SubscriptionTopicStatistics
   {
     auto received_message_age = std::make_unique<ReceivedMessageAge>();
     received_message_age->Start();
-    subscriber_statistics_collectors_.emplace_back(std::move(received_message_age));
-
     auto received_message_period = std::make_unique<ReceivedMessagePeriod>();
     received_message_period->Start();
     {
       std::lock_guard<std::mutex> lock(mutex_);
+      subscriber_statistics_collectors_.emplace_back(std::move(received_message_age));
       subscriber_statistics_collectors_.emplace_back(std::move(received_message_period));
     }
 

rclcpp/test/rclcpp/topic_statistics/test_subscription_topic_statistics.cpp

@@ -343,7 +343,6 @@ TEST_F(TestSubscriptionTopicStatisticsFixture, test_receive_stats_for_message_no
   uint64_t message_age_count{0};
   uint64_t message_period_count{0};
 
-  std::set<std::string> received_metrics;
   for (const auto & msg : received_messages) {
     if (msg.metrics_source == kMessageAgeSourceLabel) {
       message_age_count++;