[demo_nodes_cpp] add_two_ints service is flakey

[jacobperron]

Bug report

Required Info:

• Operating System:
  • OSX High Sierra
• Installation type:
  • Binary
• Version or commit hash:
  • Crystal (pre-release)
• DDS implementation:
  • Fast-RTPS
• Client library (if applicable):
  • rclcpp

Steps to reproduce issue

In one terminal start the server:

ros2 run demo_nodes_cpp add_two_ints_server

In another terminal repeatedly run the client:

ros2 run demo_nodes_cpp add_two_ints_client

The same behavior also occurs for the async client:

ros2 run demo_nodes_cpp add_two_ints_client_async

Expected behavior

Server receives clients request and client gets the response.

Actual behavior

Sometimes (~%30 of the time) the server never gets the request and the client hangs (does not return).

Additional information

Cannot reproduce with OpenSplice and Connext, which leads me to believe that this is a Fast-RTPS issue.