[foxy backport] fix test_info_by_topic flaky (#859)

rcl/test/CMakeLists.txt

@@ -129,7 +129,7 @@ function(test_target_function)
     set(AMENT_GTEST_ARGS TIMEOUT 120)
   endif()
   rcl_add_custom_gtest(test_info_by_topic${target_suffix}
-    SRCS rcl/test_info_by_topic.cpp
+    SRCS rcl/test_info_by_topic.cpp rcl/wait_for_entity_helpers.cpp
     ENV ${rmw_implementation_env_var}
     APPEND_LIBRARY_DIRS ${extra_lib_dirs}
     LIBRARIES ${PROJECT_NAME}

rcl/test/rcl/test_info_by_topic.cpp

@@ -27,6 +27,7 @@
 
 #include "rmw/topic_endpoint_info_array.h"
 #include "rmw/error_handling.h"
+#include "wait_for_entity_helpers.hpp"
 
 #include "test_msgs/msg/strings.h"
 #include "rosidl_runtime_c/string_functions.h"
@@ -357,6 +358,8 @@ TEST_F(
     &subscription_options);
   ASSERT_EQ(ret, RCL_RET_OK) << rcl_get_error_string().str;
   const std::string fqdn = std::string("/") + this->topic_name;
+  // Wait until GraphCache publishers are updated
+  ASSERT_TRUE(wait_for_graph_publication(&this->node, fqdn.c_str(), 1u, 10, 100));
   // Get publishers info by topic
   rmw_topic_endpoint_info_array_t topic_endpoint_info_array_pub =
     rmw_get_zero_initialized_topic_endpoint_info_array();
@@ -371,6 +374,9 @@ TEST_F(
   EXPECT_STREQ(topic_endpoint_info_pub.topic_type, "test_msgs/msg/Strings");
   assert_qos_equality(topic_endpoint_info_pub.qos_profile, default_qos_profile, true);
 
+  // Wait until GraphCache subcribers are updated
+  ASSERT_TRUE(wait_for_graph_subscription(&this->node, fqdn.c_str(), 1u, 10, 100));
+  // Get subscribers info by topic
   rmw_topic_endpoint_info_array_t topic_endpoint_info_array_sub =
     rmw_get_zero_initialized_topic_endpoint_info_array();
   ret = rcl_get_subscriptions_info_by_topic(

rcl/test/rcl/wait_for_entity_helpers.cpp

@@ -236,3 +236,63 @@ wait_for_subscription_to_be_ready(
   }
   return false;
 }
+
+bool
+wait_for_graph_publication(
+  const rcl_node_t * node,
+  const char * topic_name,
+  size_t count_to_wait,
+  size_t max_tries,
+  int64_t period_ms)
+{
+  if (count_to_wait == 0) {
+    return true;  // Nothing to wait
+  }
+  size_t iteration = 0;
+  while (iteration < max_tries) {
+    ++iteration;
+    size_t count;
+    rcl_ret_t ret = rcl_count_publishers(node, topic_name, &count);
+    if (ret != RCL_RET_OK) {
+      RCUTILS_LOG_ERROR_NAMED(
+        ROS_PACKAGE_NAME,
+        "Error in rcl_count_publishers: %s", rcl_get_error_string().str);
+      return false;
+    }
+    if (count == count_to_wait) {
+      return true;
+    }
+    std::this_thread::sleep_for(std::chrono::milliseconds(period_ms));
+  }
+  return false;
+}
+
+bool
+wait_for_graph_subscription(
+  const rcl_node_t * node,
+  const char * topic_name,
+  size_t count_to_wait,
+  size_t max_tries,
+  int64_t period_ms)
+{
+  if (count_to_wait == 0) {
+    return true;  // Nothing to wait
+  }
+  size_t iteration = 0;
+  while (iteration < max_tries) {
+    ++iteration;
+    size_t count;
+    rcl_ret_t ret = rcl_count_subscribers(node, topic_name, &count);
+    if (ret != RCL_RET_OK) {
+      RCUTILS_LOG_ERROR_NAMED(
+        ROS_PACKAGE_NAME,
+        "Error in rcl_count_subscribers: %s", rcl_get_error_string().str);
+      return false;
+    }
+    if (count == count_to_wait) {
+      return true;
+    }
+    std::this_thread::sleep_for(std::chrono::milliseconds(period_ms));
+  }
+  return false;
+}

rcl/test/rcl/wait_for_entity_helpers.hpp

@@ -63,4 +63,24 @@ wait_for_subscription_to_be_ready(
   size_t max_tries,
   int64_t period_ms);
 
+/// Wait for specified number of publication in GraphCache
+/// by trying at most `max_tries` times with a `period_ms` period.
+bool
+wait_for_graph_publication(
+  const rcl_node_t * node,
+  const char * topic_name,
+  size_t count_to_wait,
+  size_t max_tries,
+  int64_t period_ms);
+
+/// Wait for specified number of subcription in GraphCache
+/// by trying at most `max_tries` times with a `period_ms` period.
+bool
+wait_for_graph_subscription(
+  const rcl_node_t * node,
+  const char * topic_name,
+  size_t count_to_wait,
+  size_t max_tries,
+  int64_t period_ms);
+
 #endif  // RCL__WAIT_FOR_ENTITY_HELPERS_HPP_