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• How to handle shoot instructions, in a multiplayer TD

  - by Martin Elvar Jensen

  I'm currently working on a Multiplayer Tower Defense game, using ImpactJS & Node. I seek some clarification about how to handle projectiles from towers, let me explain. So the server is running the master game, and the clients just follow the instruction from the server. Lets say there is about 20 towers on the stage, all needs instructions for which creeps to shoot at. Now lets say each towers fires twice in a second, that's 40 shots each second, (worst case scenario) which is 40 request per second to each client, would't this casue alot of stress to the server, saying that we have 50 games running the same time. So what i am really asking, is this method inefficient, and is there a smarter way to handle all these instructions. Thank you.

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• Problem in calling a method recursively in nodejs mongodb [closed]

  - by Nilesh

  I am trying to create a tree using nodejs and mongodb.Wanted to show a path of a particulr node from the root.So I am finding the destination path and looping back to its parent iteratively until the root.So this is the snippet I am using which results in infinite looping articleProvider.finditsparent(t,function(error,tap){ if(tap[0].parent=='null') { t=(tap[0].parent); console.log(n); } else { n.push(tap[0].parent); console.log(tap[0].parent); t=(tap[0].parent); res.send(n); } }); res.send(n); }); How should I get rid of this problem?Is there any way to call it recursively?

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• Optimization of a Hybrid Pagination Scheme

  - by Kaustubh Karkare

  I'm working on a Web Application using node.js in which I'm building a partial copy of the database on the client-side to decrease the load on my server. Right now, I have a function like this (expressed as python-style pseudocode, but implemented in JavaScript): get(table_name,primary_key): if primary_key in cache[table_name]: return cache[table_name][primary_key] else: x = get_data_from_server(table_name,primary_key) # socket.io return cache[table_name][primary_key] = x While this scheme works perfectly well for caching individual rows, I'd like to extend it to support the creation of paginated tables ordered according to the primary_key, and loading additional data using the above function for only the current and possibly the adjacent pages. Now, I don't want to keep the list of primary keys on the server to be retrieved every time I need to change the page (which, for reasons beyond the scope here, will be very frequent), and keeping it on the client side, subject to real-time create/delete events from the server, doesn't seem that good an idea, even after compression (using ranges, instead of individual values). What is the best way to calculate which items are to be displayed on a random page, minimizing the space requirements & the need for communication with the server?

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• How to synchronise the acceleration, velocity and position of the monsters on the server with the players?

  - by Nick

  I'm building an MMO using Node.js, and there are monsters roaming around. I can make them move around on the server using vector variables acceleration, velocity and position. acceleration = steeringForce / mass; velocity += acceleration * dTime; position += velocity * dTime; Right now I just send the positions over, and tell the players these are the "target positions" of the monsters, and let the monsters move towards the target positions on the client with a speed dependant on the distance of the target position. It works but looks rather strange. How do I synchronise these properly with the players without looking funny to them, taking into account the server lag? The problem is that I don't know how to make use of the correct acceleration/velocity values here; right now they just move directly in a straight line to the target position instead of accelerating/braking there properly. How can I implement such behaviour?

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• What are deferred callbacks?

  - by tentimes

  I understand the idea of a callback, where I pass a function into another function and that function then uses the supplied function at will. I am struggling to understand deferred callbacks, even after googling it. Could someone provide a simple explanation please? I program in Ruby, but also know C/C++ a bit, but most of all I was a experienced assembly language programmer. So I am wondering is it a bit like a stack of callback addresses that get pop'd? I am hoping to learn jquery or node.js and these deferred callbacks seem integral to both. I understand basic threading principles (though mutex object makes my head hurt ;)

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• How to move linux executables to a ramdisk?

  - by alfa64

  i've made a ramdisk this way: mkdir -p /media/ramdisk mount -t tmpfs -o size=512M tmpfs /media/ramdisk/ The reason for this is because i run a lot of node.js scripts and their execution time is very small, but i suspect that the time overhead is because it reloads the node.js executable from disk and destroys it on each subsecuent run. So i think this might be the solution to gain a bit, if not much, performance. How can i move a program like node to the ramdisk and run it from there? The idea is to have a startup script that creates the ramdisk and puts the node files inside of it. Note that i'm currently using fedora 16 for what's it's worth. Thanks in advance.

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• Where does Rundesk execute local tasks from

  - by Leon Stafford

  I'm trying to interact with the nodejs Azure sdk from a CentOS installation of Rundeck. If I try from the "run" adhoc virtual shell, I am able to after running azure account import <mykey> and can then also execute other Azure commands inside of jobs if I set them as Rundeck node tasks and not selecting "dispatch to nodes" in the job settings. Trying to run the Azure sdk commands as commands to be dispatched to the node (local) fails with the error: localhost1-NodeDispatch-localexec 04:53:04 /usr/bin/env: node: No such file or directory 04:53:04 Failed: NonZeroResultCode: Result code was 127 I am not able to "jumpstart" the same environment by running azure account import <mykey> I am assuming this is a permissions/environmental issue, though not sure how to fix it. UPDATE: Executing whoami from the same job returns rundeck, so I assume I will need to either modify that to execute tasks as my system user or grant permissions to get the rundeck user into the node environment the Azure sdk is running in?

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• Best approach to limit users to a single node of a given content type in Drupal

  - by Chaulky

  I need to limit users to a single node of a given content type. So a user can only create one node of TypeX. I've come up with two approaches. Which would be better to use... 1) Edit the node/add/typex menu item to check the database to see if the user has already created a node of TypeX, as well as if they have permissions to create it. 2) When a user creates a node of TypeX, assign them to a different role that doesn't have permissions to create that type of node. In approach 1, I have to make an additional database call on every page load to see if they should be able to see the "Create TypeX" (node/add/typex). But in approach 2, I have to maintain two separate roles. Which approach would you use?

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• return a js file from asp.net mvc controller

  - by Erwin

  Hi all fellow programmer I'd like to have a separate js file for each MVC set I have in my application /Controllers/ -TestController.cs /Models/ /Views/ /Test/ -Index.aspx -script.js And I'd like to include the js in the Index.aspx by <script type="text/javascript" src="<%=UriHelper.GetBaseUrl()%>/Test/Js"></script> Or to put it easier, when I call http://localhost/Test/Js in the browser, it will show me the script.js file How to write the Action in the Controller? I know that this must be done with return File method, but I haven't successfully create the method :(

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• Fastest pathfinding for static node matrix

  - by Sean Martin

  I'm programming a route finding routine in VB.NET for an online game I play, and I'm searching for the fastest route finding algorithm for my map type. The game takes place in space, with thousands of solar systems connected by jump gates. The game devs have provided a DB dump containing a list of every system and the systems it can jump to. The map isn't quite a node tree, since some branches can jump to other branches - more of a matrix. What I need is a fast pathfinding algorithm. I have already implemented an A* routine and a Dijkstra's, both find the best path but are too slow for my purposes - a search that considers about 5000 nodes takes over 20 seconds to compute. A similar program on a website can do the same search in less than a second. This website claims to use D*, which I have looked into. That algorithm seems more appropriate for dynamic maps rather than one that does not change - unless I misunderstand it's premise. So is there something faster I can use for a map that is not your typical tile/polygon base? GBFS? Perhaps a DFS? Or have I likely got some problem with my A* - maybe poorly chosen heuristics or movement cost? Currently my movement cost is the length of the jump (the DB dump has solar system coordinates as well), and the heuristic is a quick euclidean calculation from the node to the goal. In case anyone has some optimizations for my A*, here is the routine that consumes about 60% of my processing time, according to my profiler. The coordinateData table contains a list of every system's coordinates, and neighborNode.distance is the distance of the jump. Private Function findDistance(ByVal startSystem As Integer, ByVal endSystem As Integer) As Integer 'hCount += 1 'If hCount Mod 0 = 0 Then 'Return hCache 'End If 'Initialize variables to be filled Dim x1, x2, y1, y2, z1, z2 As Integer 'LINQ queries for solar system data Dim systemFromData = From result In jumpDataDB.coordinateDatas Where result.systemId = startSystem Select result.x, result.y, result.z Dim systemToData = From result In jumpDataDB.coordinateDatas Where result.systemId = endSystem Select result.x, result.y, result.z 'LINQ execute 'Fill variables with solar system data for from and to system For Each solarSystem In systemFromData x1 = (solarSystem.x) y1 = (solarSystem.y) z1 = (solarSystem.z) Next For Each solarSystem In systemToData x2 = (solarSystem.x) y2 = (solarSystem.y) z2 = (solarSystem.z) Next Dim x3 = Math.Abs(x1 - x2) Dim y3 = Math.Abs(y1 - y2) Dim z3 = Math.Abs(z1 - z2) 'Calculate distance and round 'Dim distance = Math.Round(Math.Sqrt(Math.Abs((x1 - x2) ^ 2) + Math.Abs((y1 - y2) ^ 2) + Math.Abs((z1 - z2) ^ 2))) Dim distance = firstConstant * Math.Min(secondConstant * (x3 + y3 + z3), Math.Max(x3, Math.Max(y3, z3))) 'Dim distance = Math.Abs(x1 - x2) + Math.Abs(z1 - z2) + Math.Abs(y1 - y2) 'hCache = distance Return distance End Function And the main loop, the other 30% 'Begin search While openList.Count() != 0 'Set current system and move node to closed currentNode = lowestF() move(currentNode.id) For Each neighborNode In neighborNodes If Not onList(neighborNode.toSystem, 0) Then If Not onList(neighborNode.toSystem, 1) Then Dim newNode As New nodeData() newNode.id = neighborNode.toSystem newNode.parent = currentNode.id newNode.g = currentNode.g + neighborNode.distance newNode.h = findDistance(newNode.id, endSystem) newNode.f = newNode.g + newNode.h newNode.security = neighborNode.security openList.Add(newNode) shortOpenList(OLindex) = newNode.id OLindex += 1 Else Dim proposedG As Integer = currentNode.g + neighborNode.distance If proposedG < gValue(neighborNode.toSystem) Then changeParent(neighborNode.toSystem, currentNode.id, proposedG) End If End If End If Next 'Check to see if done If currentNode.id = endSystem Then Exit While End If End While If clarification is needed on my spaghetti code, I'll try to explain.

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• Reduce HTTP Requests method for js and css

  - by Giberno

  Is these way can Reduce HTTP Requests? multiple javascript files with & symbol <script type="text/javascript" src="http://yui.yahooapis.com/combo?2.5.2/build/yahoo-dom-event/yahoo-dom-event.js &http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"> </script> multiple css files with @ import <style type="text/css"> @import url(css/style.css); @import url(css/custom.css); </style>

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• Are there any alternative JS ports of Box2D?

  - by Petteri Hietavirta

  I have been thinking about creating a top down 2D car game for HTML5. For my first game I wrote the physics and collisions my self but for this one I would like to use some ready made library. I found out Box2D and its JS port. http://box2d-js.sourceforge.net It seems to be quite old port, made in 2008. Is it lacking many features of current Box2D or does it have major issues with it? And are there any alternatives for it?

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• Are there any alternative JS ports of Box2D?

  - by Petteri Hietavirta

  I have been thinking about creating a top down 2D car game for HTML5. For my first game I wrote the physics and collisions my self but for this one I would like to use some ready made library. I found out Box2D and its JS port. http://box2d-js.sourceforge.net It seems to be quite old port, made in 2008. Is it lacking many features of current Box2D or does it have major issues with it? And are there any alternatives for it?

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• Can various browsers be assumed to maintain predictible state accurately in multiplayer online gaming?

  - by Nikos

  With many games it is said that server will assume that clients keep track of the world accurately. Assuming this is true, for a browser based multiplier space invaders game you would only tell the client when new bullets or the players ship moves and everything that behaves in a predetermined manner in the js client. It would be expected that positions would be the same in the browsers. Do you think you could trust browsers to do this? I feel that timings could differ between rendering loops and cause positions to get out of sync and might just get the server to maintain all the positions to make sure.

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• JS.everywhere(2012) : deux jours autour de JavaScript pour les applications professionnelles, mi-novembre à Paris

  JS.everywhere(2012) : l'évènement autour de JavaScript pour les applications professionnelles Se tiendra mi-novembre, réduction spéciale pour les membre de Développez.com JS.everywhere(2012) est un événement européen qui se tiendra à Paris les 16 et 17 novembre prochains. Le thème de cette réunion, "JavaScript pour les applications professionnelles", fera écho à son édition américaine qui se tient un mois plus tôt dans la Silicon Valley. Comme le titre de la conférence l'indique, JavaScript est désormais partout. Il intéresse de plus en plus de développeurs d'applications métiers depuis qu'il est reconnu comme un des langages majeurs capables de gérer au...

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• Looking for a way to draw a line between two points on a sphere in Three.js

  - by speedwell

  My app (a flight tracker) needs to draw a line between two points (cities say) on a sphere (earth) along the surface (i.e. the great circle route) using Three.js. I can think of 2 ways - (a) creating Three.js 'Line' with a set of (enough) points that I calculate manually and (b) writing the lines into the texture I use for the sphere after it's loaded but before I apply it as a texture. I can see problems with both (not even sure if (b) is possible in Three.js yet) - anyone think of a better way or have an opinion? Thanks in advance.

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• HTML, JS, CSS Engines

  - by Pius

  I am just messing around, trying to figure out how stuff works and right now I have a couple questions about HTML, JS and CSS engines. I know there are two major JavaScript engines out there - V8 and JavaScriptCore (WebKit's JS engine as far as I know). Is that correct? And what are the main HTML + CSS renderers out there? Let's say I want to build a web browser using V8 (I saw it has some documentation and stuff + I like the way it works), what are the best options for me? Partially another question. Is there any bare browser that uses V8 and runs on Ubuntu at least? P.S. I am a Ubuntu user and prefer C++.

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• Is the Observer pattern adequate for this kind of scenario?

  - by Omega

  I'm creating a simple game development framework with Ruby. There is a node system. A node is a game entity, and it has position. It can have children nodes (and one parent node). Children are always drawn relatively to their parent. Nodes have a @position field. Anyone can modify it. When such position is modified, the node must update its children accordingly to properly draw them relatively to it. @position contains a Point instance (a class with x and y properties, plus some other useful methods). I need to know when a node's @position's state changes, so I can tell the node to update its children. This is easy if the programmer does something like this: @node.position = Point.new(300,300) Because it is equivalent to calling this: # Code in the Node class def position=(newValue) @position = newValue update_my_children # <--- I know that the position changed end But, I'm lost when this happens: @node.position.x = 300 The only one that knows that the position changed is the Point instance stored in the @position property of the node. But I need the node to be notified! It was at this point that I considered the Observer pattern. Basically, Point is now observable. When a node's position property is given a new Point instance (through the assignment operator), it will stop observing the previous Point it had (if any), and start observing the new one. When a Point instance gets a state change, all observers (the node owning it) will be notified, so now my node can update its children when the position changes. A problem is when this happens: @someNode.position = @anotherNode.position This means that two nodes are observing the same point. If I change one of the node's position, the other would change as well. To fix this, when a position is assigned, I plan to create a new Point instance, copy the passed argument's x and y, and store my newly created point instead of storing the passed one. Another problem I fear is this: somePoint = @node.position somePoint.x = 500 This would, technically, modify @node's position. I'm not sure if anyone would be expecting that behavior. I'm under the impression that people see Point as some kind of primitive rather than an actual object. Is this approach even reasonable? Reasons I'm feeling skeptical: I've heard that the Observer pattern should be used with, well, many observers. Technically, in this scenario there is only one observer at a time. When assigning a node's position as another's (@someNode.position = @anotherNode.position), where I create a whole new instance rather than storing the passed point, it feels hackish, or even inefficient.

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• Loading Nested JS Files on the Page

  - by Aidin

  Hi, I have a JS file that is dependent to another Js file. this Js file is something like this (Common.js) //Some codes here window.onload = PageLoad; //some codes here and then I implement PageLoad function in another Js file. ( I do this because every page has its own PageLoad implementation) and I Load these files like this on my Main.aspx : `<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">` `<\script language="javascript" type="text/javascript" src="PagesJS/pgeMain.js"></script>` `<\script language="javascript" type="text/javascript" src="JS/Common.js"></script>` ... ... `</asp:Content>` Every thing works fine on local but when I deploy it, sometimes I get PageLoad undefined Error! Can any one tells me what is wrong with this? Thanks. Aidin

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• How to store session values with Node.js and mongodb?

  - by Tirithen

  How do I get sessions working with Node.js, [email protected] and mongodb? I'm now trying to use connect-mongo like this: var config = require('../config'), express = require('express'), MongoStore = require('connect-mongo'), server = express.createServer(); server.configure(function() { server.use(express.logger()); server.use(express.methodOverride()); server.use(express.static(config.staticPath)); server.use(express.bodyParser()); server.use(express.cookieParser()); server.use(express.session({ store: new MongoStore({ db: config.db }), secret: config.salt })); }); server.configure('development', function() { server.use(express.errorHandler({ dumpExceptions: true, showStack: true })); }); server.configure('production', function() { server.use(express.errorHandler()); }); server.set('views', __dirname + '/../views'); server.set('view engine', 'jade'); server.listen(config.port); I'm then, in a server.get callback trying to use req.session.test = 'hello'; to store that value in the session, but it's not stored between the requests. It probobly takes something more that this to store session values, how? Is there a better documented module than connect-mongo?

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• node.js: looping, email each matching row from query but it it emails the same user by # number of matches?

  - by udonsoup16

  I have a node.js email server that works fine however I noticed a problem. If the query string found 4 rows, it would send four emails but only to the first result instead of to each found email address. var querystring1 = 'SELECT `date_created`,`first_name`,`last_name`,`email` FROM `users` WHERE TIMESTAMPDIFF(SECOND,date_created, NOW()) <=298 AND `email`!="" LIMIT 0,5'; connection.query(querystring1, function (err, row) { if (err) throw err; for (var i in row) { // Email content; change text to html to have html emails. row[i].column name will pull relevant database info var sendit = { to: row[i].email, from: '******@******', subject: 'Hi ' + row[i].first_name + ', Thanks for joining ******!', html: {path:__dirname + '/templates/welcome.html'} }; // Send emails transporter.sendMail(sendit,function(error,response){ if (error) { console.log(error); }else{ console.log("Message sent1: " + row[i].first_name);} transporter.close();} ) }}); .... How do I have it loop through each found row and send a custom email using row data individual row data?

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• How much overhead is there in persistent connections?

  - by nynex

  Ok so I'm musing over a little side project I want to start. Essentially its a multi-session web based FTP client. Multi-session in that you can log into several FTP servers at the same time and perform operations like moving a file from one FTP server to another. I'm doing this mainly to brush up on the new webdev technologies, particularly websockets. I'm using node.js + socket.io to keep a persistent bi-directional connection between the web browser and the web server. The web server will also have persistent connections to each FTP server the user has logged into. So if there are 100 concurrent users each logged into 5 ftp accounts, the web server will have 100 websocket connections + 500 ftp connections. Is servicing 600 connections a lot? I know it depends on the hardware resources of the server but is something like this doable on a budget? Are there more efficient means of doing something like this? I know its unlikely that this project will really get popular but I want it to scale well regardless. Thanks for any help, I've still got a lot to learn.

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• How to unit test models in MVC / MVR app?

  - by BBnyc

  I'm building a node.js web app and am trying to do so for the first time in a test driven fashion. I'm using nodeunit for testing, which I find allows me to write tests quickly and painlessly. In this particular app, the heavy lifting primarily involves translating SQL data into complex Javascript object and serving them to the front-end via json. Likewise, the app also spends a great deal of code validating and translating complex, multidimensional Javascript objects it receives from the front-end into SQL rows. Hence I have used a fat model design for the app -- most of the real code resides in the models, where the data translation happens. What's the best approach to test such models with unit tests? I mean in particular the methods that have create javascript objects from the SQL rows and serve them to the front-end. Right now what I'm doing is making particular requests of my models with the unit tests and checking the returned data for all of the fields that should be there. However I have a suspicion that this is not the most robust kind of testing I could be doing. My current testing design also means I have to package my app code with some dummy data so that my tests can anticipate the kind of data that the app should be returning when tests run.

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• why are transaction monitors on decline? or are they?

  - by mrkafk

  http://www.itjobswatch.co.uk/jobs/uk/cics.do http://www.itjobswatch.co.uk/jobs/uk/tuxedo.do Look at the demand for programmers (% of job ads that the keyword appears), first graph under the table. It seems like demand for CICS, Tuxedo has fallen from 2.5%/1% respectively to almost zero. To me, it seems bizarre: now we have more networked and internet enabled machines than ever before. And most of them are talking to some kind of database. So it would seem that use of products whose developers spent last 20-30 years working on distributing and coordinating and optimizing transactions should be on the rise. And it appears they're not. I can see a few causes but can't tell whether they are true: we forgot that concurrency and distribution are really hard, and redoing it all by ourselves, in Java, badly. Erlang killed them all. Projects nowadays have changed character, like most business software has already been built and we're all doing internet services, using stuff like Node.js, Erlang, Haskell. (I've used RabbitMQ which is written in Erlang, "but it was small specialized side project" kind of thing). BigData is the emphasis now and BigData doesn't need transactions very much (?). None of those explanations seem particularly convincing to me, which is why I'm looking for better one. Anyone?

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• How to build an API on top of an existing Rails app with NodeJs and what architecture to use?

  - by javiayala

  The explanation I was recently hired by a company that has an old RoR 2.3 application with more than 100k users, a strong SEO strategy with more than 170k indexed urls, native android and ios applications and other custom-made mobile and web applications that rely on a not so good API from the same RoR app. They recently merged with a company from another country as an strategy to grow the business and the profit. They have almost the same stats, a similar strategy and mobile apps. We have just decided that we need to merge the data from both companies and to start a new app from scratch since the RoR app is to old and heavily patched and the app from the other company was built with a custom PHP framework without any documentation. The only good news is that both databases are in MySQL and have a similar structure. The challenge I need to build a new version that: can handle a lot of traffic, preserves the SEO strategies of both companies, serve 2 different domains, and have a strong API that can support legacy mobile apps from both companies and be ready for a new set of native apps. I want to use RoR 3.2 for the main web apps and NodeJs with a Restful API. I know that I need to be very careful with the mobile apps and handle multiple versions of the API. I also think that I need to create a service that can handle a lot IO request since the apps is heavily used to create orders for restaurants at a certain time of the day. The questions With all this in mind: What type of architecture do you recommend me to follow? What gems or node packages do you think will work the best? How do I build a new rails app and keep using the same database structure? Should I use NodeJS to build an API or just build a new service with Ruby? I know that I'm asking to much from you guys, but please help me by answering any topic that you can or by pointing me on the right direction. All your comments and feedback will be extremely appreciated! Thanks!

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