Change default to synchronous (#571)

* Change default to synchronous

Signed-off-by: Audrow Nash <[email protected]>

README.md

@@ -55,7 +55,7 @@ This entails that any blocking call occurring during the write operation would b
 It is important to note that this mode typically yields higher throughput rates at lower latencies, since the notification and context switching between threads is not present.
 * `AUTO`: let Fast DDS select the publication mode. This implies using the publication mode set in the XML file or, failing that, the default value set in Fast DDS (which currently is set to `SYNCHRONOUS`).
 
-If `RMW_FASTRTPS_PUBLICATION_MODE` is not set, then both `rmw_fastrtps_cpp` and `rmw_fastrtps_dynamic_cpp` behave as if it were set to `ASYNCHRONOUS`.
+If `RMW_FASTRTPS_PUBLICATION_MODE` is not set, then both `rmw_fastrtps_cpp` and `rmw_fastrtps_dynamic_cpp` behave as if it were set to `SYNCHRONOUS`.
 
 ### Full QoS configuration
 

rmw_fastrtps_shared_cpp/src/participant.cpp

@@ -189,7 +189,7 @@ rmw_fastrtps_shared_cpp::create_participant(
   domainParticipantQos.name(enclave);
 
   bool leave_middleware_default_qos = false;
-  publishing_mode_t publishing_mode = publishing_mode_t::ASYNCHRONOUS;
+  publishing_mode_t publishing_mode = publishing_mode_t::SYNCHRONOUS;
   const char * env_value;
   const char * error_str;
   error_str = rcutils_get_env("RMW_FASTRTPS_USE_QOS_FROM_XML", &env_value);
@@ -207,16 +207,17 @@ rmw_fastrtps_shared_cpp::create_participant(
       return nullptr;
     }
     if (env_value != nullptr) {
-      // Synchronous publishing
       if (strcmp(env_value, "SYNCHRONOUS") == 0) {
         publishing_mode = publishing_mode_t::SYNCHRONOUS;
+      } else if (strcmp(env_value, "ASYNCHRONOUS") == 0) {
+        publishing_mode = publishing_mode_t::ASYNCHRONOUS;
       } else if (strcmp(env_value, "AUTO") == 0) {
         publishing_mode = publishing_mode_t::AUTO;
-      } else if (strcmp(env_value, "ASYNCHRONOUS") != 0 && strcmp(env_value, "") != 0) {
+      } else if (strcmp(env_value, "") != 0) {
         RCUTILS_LOG_WARN_NAMED(
           "rmw_fastrtps_shared_cpp",
           "Value %s unknown for environment variable RMW_FASTRTPS_PUBLICATION_MODE"
-          ". Using default ASYNCHRONOUS publishing mode.", env_value);
+          ". Using default SYNCHRONOUS publishing mode.", env_value);
       }
     }
   }