Rework MQTTPushers halt() method: now supports timeout

dcdbpusher/MQTTPusher.cpp

@@ -242,6 +242,23 @@ bool MQTTPusher::sendMappings() {
 	return true;
 }
 
+bool MQTTPusher::halt(unsigned short timeout) {
+    _doHalt = true;
+
+    for (unsigned short i = 1; i <= timeout; i++) {
+        if (_halted) {
+            return true;
+        } else {
+            LOGM(info) << "Waiting for push cycle to pause... (" << i << "/" << timeout << ")";
+            sleep(1);
+        }
+    }
+
+    cont();
+    LOGM(info) << "Timeout: push cycle did not pause. Continuing...";
+    return false;
+}
+
 void MQTTPusher::computeMsgRate() {
 	// Computing number of sent MQTT messages per second
 	float msgRate = 0;

dcdbpusher/MQTTPusher.h

@@ -28,30 +28,59 @@ public:
 			   pluginVector_t& plugins, an_pluginVector_t& aPlugins, int maxNumberOfMessages, unsigned int maxInflightMsgNum, unsigned int maxQueuedMsgNum);
 	virtual ~MQTTPusher();
 
+	/**
+	 * @brief MQTTPusher's main execution loop.
+	 *
+	 * @details If MQTTPusher is started this function runs indefinitely until
+	 *          a call to stop(). Execution of the main loop can be halted and
+	 *          continued with halt() and cont() respectively.
+	 */
 	void push();
+
+	/**
+	 * @brief
+	 *
+	 * @return
+	 */
 	bool sendMappings();
 
+	/**
+	 * @brief Start MQTTPusher's push loop.
+	 */
 	void start() {
 		_keepRunning = true;
 	}
 
+	/**
+	 * @brief Stop MQTTPusher's push loop and terminate its execution.
+	 */
 	void stop() {
 		_keepRunning = false;
 	}
 
-	void halt() {
-		_doHalt = true;
-	}
+	/**
+	 * @brief Blocking call to pause MQTTPusher's push loop.
+	 *
+	 * @details Instructs MQTTPusher to pause its push loop and blocks until
+	 *          MQTTPusher is actually paused or a timeout occurred. On a
+	 *          timeout execution of MQTTPusher is continued.
+	 *
+	 * @param timeout Time in seconds to wait for MQTTPusher to finish its
+	 *                current push cycle.
+	 *
+	 * @return True if MQTTPusher was succesfully paused, false if a timeout
+	 *         occurred and MQTTPusher still runs.
+	 */
+	bool halt(unsigned short timeout = 5);
 
+	/**
+	 * @brief Continue MQTTPusher's push loop.
+	 */
 	void cont() {
 		computeMsgRate();
 		_doHalt = false;
 	}
 
-	bool isHalted() const {
-		return _halted;
-	}
-
 private:
 	int sendReadings(SensorBase& s, reading_t* reads, std::size_t& totalCount);
 	void computeMsgRate();

dcdbpusher/RestAPI.cpp

@@ -228,11 +228,12 @@ void RestAPI::PUT_reload(endpointArgs) {
         if (p.id == plugin) {
             //before modifying the plugin we need to ensure that we have exclusive access
             //therefore pause the only other concurrent user (MQTTPusher)
-            _mqttPusher->halt();
-            //wait until MQTTPusher is paused
-            while (!_mqttPusher->isHalted()) {
-                sleep(1);
+            if (!_mqttPusher->halt()) {
+                res.body() = "Could not reload plugin (Timeout while waiting).\n";
+                res.result(http::status::internal_server_error);
+                return;
             }
+
             // Removing obsolete MQTT topics
             removeTopics(p);
             if (p.configurator->reReadConfig()) {
@@ -313,35 +314,21 @@ void RestAPI::PUT_analytics_reload(endpointArgs) {
 
     const std::string plugin   = getQuery("plugin", queries);
 
-    //Pause mqttPusherin order to reload plugins
-    _mqttPusher->halt();
-    unsigned short retryWait = 0;
-
     // Wait until MQTTPusher is paused in order to reload plugins
-    //do not wait longer than 10 seconds for mqttPusher to halt
-    //TODO implement timeout query
-    for (unsigned short i = 1; i < 6; i++) {
-        if (_mqttPusher->isHalted()) {
-            if (!_manager->reload(_io, plugin)) {
-                res.body() = "Plugin not found or reload failed, please check the config files and MQTT topics!\n";
-                res.result(http::status::not_found);
-            } else if (!_manager->start(plugin)){
-                res.body() = "Plugin cannot be restarted!\n";
-                res.result(http::status::internal_server_error);
-            } else {
-                res.body() = "Plugin " + plugin + ": Sensors reloaded\n";
-                res.result(http::status::ok);
-            }
-            _mqttPusher->cont();
-            return;
+    if (_mqttPusher->halt()) {
+        if (!_manager->reload(_io, plugin)) {
+            res.body() = "Plugin not found or reload failed, please check the config files and MQTT topics!\n";
+            res.result(http::status::not_found);
+        } else if (!_manager->start(plugin)){
+            res.body() = "Plugin cannot be restarted!\n";
+            res.result(http::status::internal_server_error);
         } else {
-            ServerLOG(info) << "Waiting for MQTTPusher to halt ...(" << i << "/" << "5)";
-            sleep(1);
+            res.body() = "Plugin " + plugin + ": Sensors reloaded\n";
+            res.result(http::status::ok);
         }
+        _mqttPusher->cont();
+    } else {
+        res.body() = "Could not reload plugins (Timeout while waiting).\n";
+        res.result(http::status::internal_server_error);
     }
-
-    _mqttPusher->cont();
-    ServerLOG(info) << "Not waiting any longer for MQTTPusher";
-    res.body() = "Could not reload plugins (Timeout while waiting).\n";
-    res.result(http::status::internal_server_error);
 }