Task persistence after shutdown

index.js

@@ -10,8 +10,7 @@ let addRequestId = require('./libs/expressRequestId')();
 let multer = require('multer');
 let bodyParser = require('body-parser');
 let morgan = require('morgan');
-
-let taskManager = new (require('./libs/taskManager'))();
+let TaskManager = require('./libs/taskManager');
 let Task = require('./libs/Task');
 
 app.use(morgan('tiny'));
@@ -112,6 +111,35 @@ app.post('/task/restart', uuidCheck, (req, res) => {
 	taskManager.restart(req.body.uuid, successHandler(res));
 });
 
-app.listen(3000, () => {
-  console.log('Server has started on port 3000');
-});
+let gracefulShutdown = done => {
+	async.series([
+		cb => { taskManager.dumpTaskList(cb) },
+		cb => { 
+			console.log("Closing server");
+			server.close();
+			console.log("Exiting...");
+			process.exit(0);
+		}
+	], done);
+};
+
+// listen for TERM signal .e.g. kill 
+process.on ('SIGTERM', gracefulShutdown);
+
+// listen for INT signal e.g. Ctrl-C
+process.on ('SIGINT', gracefulShutdown);
+
+// Startup
+let taskManager;
+let server;
+
+async.series([
+	cb => { taskManager = new TaskManager(cb); },
+	cb => { server = app.listen(3000, err => {
+			if (!err) console.log('Server has started on port 3000');
+			cb(err);
+		});
+	}
+], err => {
+	if (err) console.log("Error during startup: " + err.message);
+});

libs/Task.js

@@ -7,9 +7,9 @@ let odmRunner = require('./odmRunner');
 let statusCodes = require('./statusCodes');
 
 module.exports = class Task{
-	constructor(uuid, name, readyCb){
+	constructor(uuid, name, done){
 		assert(uuid !== undefined, "uuid must be set");
-		assert(readyCb !== undefined, "ready must be set");
+		assert(done !== undefined, "ready must be set");
 
 		this.uuid = uuid;
 		this.name = name != "" ? name : "Task of " + (new Date()).toISOString();
@@ -22,14 +22,33 @@ module.exports = class Task{
 
 		// Read images info
 		fs.readdir(this.getImagesFolderPath(), (err, files) => {
-			if (err) readyCb(err);
+			if (err) done(err);
 			else{
 				this.images = files;
-				readyCb(null, this);
+				done(null, this);
 			}
 		});
 	}
 
+	static CreateFromSerialized(taskJson, done){
+		new Task(taskJson.uuid, taskJson.name, (err, task) => {
+			if (err) done(err);
+			else{
+				// Override default values with those
+				// provided in the taskJson
+				for (let k in taskJson){
+					task[k] = taskJson[k];
+				}
+				
+				// Tasks that were running should be put back to QUEUED state
+				if (task.status.code === statusCodes.RUNNING){
+					task.status.code = statusCodes.QUEUED;
+				}
+				done(null, task);
+			}
+		})
+	}
+
 	// Get path where images are stored for this task
 	// (relative to nodejs process CWD)
 	getImagesFolderPath(){
@@ -176,4 +195,16 @@ module.exports = class Task{
 	getOutput(startFromLine = 0){
 		return this.output.slice(startFromLine, this.output.length);
 	}
+
+	// Returns the data necessary to serialize this
+	// task to restore it later.
+	serialize(){
+		return {
+			uuid: this.uuid,
+			name: this.name,
+			dateCreated: this.dateCreated,
+			status: this.status,
+			options: this.options
+		}
+	}
 };

libs/TaskManager.js

@@ -1,14 +1,51 @@
 "use strict";
 let assert = require('assert');
+let fs = require('fs');
 let Task = require('./Task');
 let statusCodes = require('./statusCodes');
+let async = require('async');
 
-let PARALLEL_QUEUE_PROCESS_LIMIT = 2;
+const PARALLEL_QUEUE_PROCESS_LIMIT = 2;
+const TASKS_DUMP_FILE = "data/tasks.json";
 
 module.exports = class TaskManager{
-	constructor(){
+	constructor(done){
 		this.tasks = {};
 		this.runningQueue = [];
+
+		async.series([
+			cb => { this.restoreTaskListFromDump(cb); },
+			cb => {
+				this.processNextTask();
+				cb();
+			}
+		], done);
+		
+	}
+
+	// Load tasks that already exists (if any)
+	restoreTaskListFromDump(done){
+		fs.readFile(TASKS_DUMP_FILE, (err, data) => {
+			if (!err){
+				let tasks = JSON.parse(data.toString());
+
+				async.each(tasks, (taskJson, done) => {
+					Task.CreateFromSerialized(taskJson, (err, task) => {
+						if (err) done(err);
+						else{
+							this.tasks[task.uuid] = task;
+							done();
+						}
+					});
+				}, err => {
+					console.log(`Initialized ${tasks.length} tasks`);
+					if (done !== undefined) done();
+				});				
+			}else{
+				console.log("No tasks dump found");
+				if (done !== undefined) done();
+			}
+		});
 	}
 
 	// Finds the first QUEUED task.
@@ -113,4 +150,20 @@ module.exports = class TaskManager{
 		if (!task && cb) cb(new Error(`${uuid} not found`));
 		return task;
 	}
+
+	// Serializes the list of tasks and saves it
+	// to disk
+	dumpTaskList(done){
+		var output = [];
+
+		for (let uuid in this.tasks){
+			output.push(this.tasks[uuid].serialize());
+		}
+
+		fs.writeFile(TASKS_DUMP_FILE, JSON.stringify(output), err => {
+			if (err) console.log(`Could not dump tasks: ${err.message}`);
+			else console.log("Dumped tasks list.");
+			if (done !== undefined) done();
+		})
+	}
 };