finished and tested the initial version of smart parking based fog fu…

…nctions

application/fogfunction/javascript/build

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+npm install  
+docker build -t "fogflow/connectedcar"  .

application/fogfunction/javascript/dockerfile

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+FROM mhart/alpine-node
+
+WORKDIR /app
+ADD . /app
+ENTRYPOINT [ "node", "main.js" ]

application/fogfunction/javascript/function.js

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+//  define global variables or include third-party libraries (notice that the library must be specified in the package.json file as well)
+var speakerID = null;
+
+//
+//  contextEntity: the received entities
+//  publish, query, and subscribe are the callback functions for your own function to interact with the assigned nearby broker
+//      publish:    publish the generated entity, which could be a new entity or the update of an existing entity
+//      query:      query addtional information from the assigned nearby broker
+//      subscribe:  subscribe addtional infromation from the assigned nearby broker
+//
+exports.handler = function(contextEntity, publish, query, subscribe)
+{
+	console.log("enter into the user-defined fog function");
+
+	if (contextEntity == null) {
+		return;
+	} 	
+	if (contextEntity.attributes == null) {
+		return;
+	}
+
+    // ============================== publish ======================================================
+
+    // if you need to publish the generated result, please refer to the following example    
+
+    /*
+    var updateEntity = {};
+    updateEntity.entityId = {
+           id: "Twin.Home.0001",
+           type: 'Home',
+           isPattern: false
+    };	    	
+    updateEntity.attributes = {};	 
+    updateEntity.attributes.city = {type: 'string', value: 'Heidelberg'};                
+    
+    updateEntity.metadata = {};    
+    updateEntity.metadata.location = {
+        type: 'point',
+        value: {'latitude': 33.0, 'longitude': -1.0}
+    };        
+   	
+    publish(updateEntity);
+    console.log("publish: ", updateEntity);		                
+    */
+
+
+    // ============================== query ======================================================
+
+    // if you want to query addtional information from the assigned nearby broker, please refer to the following example
+
+    /*
+    var queryReq = {}
+    queryReq.entities = [{type:'PublicSite', isPattern: true}];    
+    var handleQueryResult = function(entityList) {
+        for(var i=0; i<entityList.length; i++) {
+            var entity = entityList[i];
+            console.log('===============' + i + '===================');
+            console.log(entity);   
+        }
+    }  
+    
+    query(queryReq, handleQueryResult);
+    */
+
+
+    // ============================== subscribe ======================================================
+
+    // if you want to subscribe addtional infromation from the assigned nearby broker, please refer to the following example
+
+    /*
+    var subscribeCtxReq = {};    
+    subscribeCtxReq.entities = [{type: 'Home', isPattern: true}];
+    subscribeCtxReq.attributes = ['alert'];        
+    //subscribeCtxReq.restriction = {scopes: [{scopeType: 'stringQuery', scopeValue: 'geohash='+contextEntity.attributes.geohash.value}]}        	
+    
+    subscribe(subscribeCtxReq);     
+    */
+
+};
+

application/fogfunction/javascript/main.js

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+'use strict';
+
+const NGSIClient = require('./ngsi/ngsiclient.js');
+const NGSIAgent = require('./ngsi/ngsiagent.js');
+const fogfunction = require('./function.js');
+
+var ngsi10client = null;
+var brokerURL;
+var outputs = [];
+var threshold = 30;
+var myReferenceURL;
+var mySubscriptionId = null;
+var isConfigured = false;
+
+var buffer = [];
+
+function startApp() 
+{
+    console.log('start to receive input data streams via a listening port');
+}
+
+function stopApp() 
+{
+	console.log('clean up the app');
+}
+
+// handle the commands received from the engine
+function handleAdmin(req, commands, res) 
+{	
+    console.log('=============configuration commands=============');
+    console.log(commands);
+
+	handleCmds(commands);
+
+	isConfigured = true;
+
+	res.status(200).json({});
+}
+
+function handleCmds(commands) 
+{
+	for(var i = 0; i < commands.length; i++) {
+		var cmd = commands[i];
+        console.log(cmd);
+		handleCmd(cmd);
+        console.log("handle next command");
+	}	
+
+	// send the updates in the buffer
+	sendUpdateWithinBuffer();
+}
+
+function handleCmd(commandObj) 
+{
+    if (commandObj.command == 'CONNECT_BROKER') {        
+		connectBroker(commandObj);
+    } else if (commandObj.command == 'SET_OUTPUTS') {        
+		setOutputs(commandObj);
+    } else if (commandObj.command == 'SET_REFERENCE'){
+        setReferenceURL(commandObj);
+	}
+}
+
+// connect to the IoT Broker
+function connectBroker(cmd) 
+{
+    brokerURL = cmd.brokerURL;
+    ngsi10client = new NGSIClient.NGSI10Client(brokerURL);
+	console.log('connected to broker', cmd.brokerURL);
+}
+
+function setReferenceURL(cmd) 
+{
+    myReferenceURL = cmd.url   
+	console.log('your application can subscribe addtional inputs under the reference URL: ', myReferenceURL);
+}
+
+
+function setOutputs(cmd) 
+{
+	var outputStream = {};
+	outputStream.id = cmd.id;
+	outputStream.type = cmd.type;
+
+	outputs.push(outputStream);
+
+	console.log('output has been set: ', cmd);
+}
+
+function sendUpdateWithinBuffer()
+{
+	for(var i=0; i<buffer.length; i++){
+		var tmp = buffer[i];
+
+		if (tmp.outputIdx > 0) {
+			tmp.ctxObj.entityId.id = outputs[i].id;
+			tmp.ctxObj.entityId.type = outputs[i].type;
+		}
+
+    	ngsi10client.updateContext(tmp.ctxObj).then( function(data) {
+		console.log('======send update======');
+    	    console.log(data);
+    	}).catch(function(error) {
+		console.log(error);
+    	    console.log('failed to update context');
+    	});  		
+	}
+
+	buffer= [];
+}
+
+//
+// query results from the assigned nearby IoT broker
+//
+function query(queryCtxReq, f)
+{    
+	if (ngsi10client == null) {
+        console.log("=== broker is not configured for your query");
+		return
+	}
+
+    ngsi10client.queryContext(queryCtxReq).then(f).catch( function(error) {
+        console.log('failed to subscribe context');
+    });
+}
+
+//
+// send subscriptions to IoT broker
+//
+function subscribe(subscribeCtxReq)
+{
+	if (ngsi10client == null) {
+        console.log("=== broker is not configured for your subscription");
+		return
+	}    
+
+    subscribeCtxReq.reference =  myReferenceURL;
+
+	console.log("================trigger my own subscription===================");
+	console.log(subscribeCtxReq);
+
+    ngsi10client.subscribeContext(subscribeCtxReq).then( function(subscriptionId) {		
+        console.log("subscription id = " + subscriptionId);   
+		mySubscriptionId = subscriptionId;
+    }).catch(function(error) {
+        console.log('failed to subscribe context');
+    });
+}	
+
+//
+// publish context entities: 
+//
+function publish(ctxUpdate)
+{
+	buffer.push(ctxUpdate)
+
+	if (ngsi10client == null) {
+        console.log("=== broker is not configured for your update");
+		return
+	}
+
+	for(var i=0; i<buffer.length; i++){
+		var update = buffer[i];
+
+    	ngsi10client.updateContext(update).then( function(data) {
+		    console.log('======send update======');
+    	    console.log(data);
+    	}).catch(function(error) {
+		    console.log(error);
+    	    console.log('failed to update context');
+    	});  		
+	}
+
+	buffer= [];
+}
+
+// handle the received results
+function handleNotify(req, ctxObjects, res) 
+{	
+	console.log('============handle notify==========================');
+	for(var i = 0; i < ctxObjects.length; i++) {
+		console.log(ctxObjects[i]);
+        fogfunction.handler(ctxObjects[i], publish, query, subscribe);
+	}
+}
+
+// get the listening port number from the environment variables given by the FogFlow edge worker
+var myport = process.env.myport;
+
+// set up the NGSI agent to listen on 
+NGSIAgent.setNotifyHandler(handleNotify);
+NGSIAgent.setAdminHandler(handleAdmin);
+NGSIAgent.start(myport, startApp);
+
+process.on('SIGINT', function() {
+	NGSIAgent.stop();	
+	stopApp();
+
+	process.exit(0);
+});
+
+