Add heart beat check to an asynchronous callback.

coupler/opc-ua-server/coupler1.sh

 #!/bin/bash
-./server -m 1 -b 1 -i 1 -l 2,3 -t 100
+./server -m 1 -b 1 -i 1 -l 2,3 -t 500

coupler/opc-ua-server/coupler2.sh

 #!/bin/bash
-./server -p 4841 -m 1 -b 1 -i 2 -l 1,3 -t 100
+./server -p 4841 -m 1 -b 1 -i 2 -l 1,3 -t 500

coupler/opc-ua-server/coupler3.sh

 #!/bin/bash
-./server -p 4842 -m 1 -b 1 -i 3 -l 1,2 -t 100
+./server -p 4842 -m 1 -b 1 -i 3 -l 1,2 -t 500

coupler/opc-ua-server/keep_alive_subscriber.h

@@ -41,26 +41,6 @@ static void dataChangeNotificationCallback(UA_Server *server, UA_UInt32 monitore
           // convert micro seconds to str
           char* micro_seconds_str = convertLongInt2Str(micro_seconds);
 
-          // XXX: implement check for dead couplers using asynchronous callbacks from open62541
-          int i, id;
-          size_t n = sizeof(HEART_BEAT_ID_LIST)/sizeof(HEART_BEAT_ID_LIST[0]);
-          for (int i = 0; i < n; i++) {
-            id = HEART_BEAT_ID_LIST[i];
-            if (id > 0) {
-              // convert to str as this is the hash key
-              char* id_str = convertInt2Str(id);
-              char *last_seen_timestamp = getItem(SUBSCRIBER_DICT, id_str);
-              UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "\tcheck ID=%s, last_seen=%s", id_str, last_seen_timestamp);
-              if (last_seen_timestamp!=NULL){
-                // we do have timestamp for this coupler ID
-                int last_seen_timestamp_int = atoi(last_seen_timestamp);
-                int timestamp_delta = micro_seconds - last_seen_timestamp_int;
-                bool is_down = (timestamp_delta > 1000);
-                UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "\t\tdelta=%d, is_down=%d", timestamp_delta, is_down);
-              }
-            }
-          }
-
           // Add to our local linked list
           addItem(&SUBSCRIBER_DICT, coupler_id_str, micro_seconds_str);
 
@@ -275,6 +255,30 @@ static void fillTestDataSetMetaData(UA_DataSetMetaDataType *pMetaData) {
     pMetaData->fields[1].valueRank = -1; /* scalar */
 }
 
+
+void callbackCheckHeartBeat() {
+  int i, coupler_id;
+  long int micro_seconds = getMicroSeconds();
+  size_t n = sizeof(HEART_BEAT_ID_LIST)/sizeof(HEART_BEAT_ID_LIST[0]);
+  for (int i = 0; i < n; i++) {
+    coupler_id = HEART_BEAT_ID_LIST[i];
+    if (coupler_id > 0) {
+      // convert to str as this is the hash key
+      char* coupler_id_str = convertInt2Str(coupler_id);
+      char *last_seen_timestamp = getItem(SUBSCRIBER_DICT, coupler_id_str);
+      UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "Check ID=%s, last_seen=%s", coupler_id_str, last_seen_timestamp);
+      if (last_seen_timestamp != NULL){
+        // we do have timestamp for this coupler ID
+        int last_seen_timestamp_int = atoi(last_seen_timestamp);
+        int timestamp_delta = micro_seconds - last_seen_timestamp_int;
+        bool is_down = (timestamp_delta > 1000);
+        UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "\tdelta=%d, is_down=%d", timestamp_delta, is_down);
+      }
+    }
+  }
+}
+
+
 static int enableSubscribeToHeartBeat(UA_Server *server, UA_ServerConfig *config){
     // enable subscribe to keep-alive messages
     UA_String transportProfile = UA_STRING(DEFAULT_TRANSPORT_PROFILE);
@@ -289,4 +293,8 @@ static int enableSubscribeToHeartBeat(UA_Server *server, UA_ServerConfig *config
 
     /* Add SubscribedVariables to the created DataSetReader */
     addSubscribedVariables(server, readerIdentifier);
+
+   // add a callback which will check related coupler's heart beats
+   UA_UInt64 callbackId = 2;
+   UA_Server_addRepeatedCallback(server, callbackCheckHeartBeat, NULL, HEART_BEAT_INTERVAL, &callbackId);
 }