I use python script to do some calculations in the backend. The proccess works as follows:
I create a list of variables by clicking on some items in the app
That list is sent to the python script and it sends back a json back
Based on that json file i display a table
Then the list of variables is ereased and I can do this again
But here is the problem, when I run this locally on c9.io, lets say I give the address of that c9.io to someone, then when that person is clicking on variables to add to that list, he adds them to the same list as I do. There are no separate lists for other people when using the app from different ip or something and therefore it gets confusing because when I send to python script I get json file with results i didnt want, but someone else did.
But then Im planning on hosting it on heroku and I wonder if it will be working differently, so when someone is using the app from there he gets his own list of the variables and it wont be shared by everyone who is using this at the same time as someone. Or is there a some way to do this specifically?
Here is the backend code for the app:
First this is the code for adding items to the list and here is the problem since anyone if doing it at the same time will be adding to the same list
var jsondata = ""
var thelist =[]
app.get("/show/:id", function (req, res) {
var id = req.params.id;
thelist.push(id)
console.log(thelist);
res.redirect('/')
});
Then the rest (so running the script and emptying the list)
app.get("/run", function(req, res) {
var pyshell = new PythonShell('script.py');
pyshell.send(JSON.stringify(thelist))
pyshell.on('message', function (message) {
// received a message sent from the Python script (a simple "print" statement)
jsondata += message
});
// end the input stream and allow the process to exit
pyshell.end(function (err) {
if (err){
throw err;
};
console.log(jsondata);
});
thelist = []
});
app.get('/data', function(req, res) {
if (jsondata == "") {
res.redirect('/')
} else {
//viewname can include or omit the filename extension
res.render("data", {data: JSON.parse(jsondata)} )
jsondata = ""}
});
So I think i need those two variables jsondata and thelist need to be somehow coded in a way that they are seprate for every unique user (as in accessing the app from different place, so the app would be run as a separate session for each user that accesses it (but also no need for registration) )
Related
I have a Node.js server which queries MySQL database. It serves as an api end point where it returns JSON and also backend server for my Express application where it returns the retrieved list as an object to the view.
I am looking into implementing flat-cache for increasing the response time. Below is the code snippet.
const flatCache = require('flat-cache');
var cache = flatCache.load('productsCache');
//get all products for the given customer id
router.get('/all/:customer_id', flatCacheMiddleware, function(req, res){
var customerId = req.params.customer_id;
//implemented custom handler for querying
queryHandler.queryRecordsWithParam('select * from products where idCustomers = ? order by CreatedDateTime DESC', customerId, function(err, rows){
if(err) {
res.status(500).send(err.message);
return;
}
res.status(200).send(rows);
});
});
//caching middleware
function flatCacheMiddleware(req, res, next) {
var key = '__express__' + req.originalUrl || req.url;
var cacheContent = cache.getKey(key);
if(cacheContent){
res.send(cacheContent);
} else{
res.sendResponse = res.send;
res.send = (body) => {
cache.setKey(key,body);
cache.save();
res.sendResponse(body)
}
next();
}
}
I ran the node.js server locally and the caching has indeed greatly reduced the response time.
However there are two issues I am facing that I need your help with.
Before putting that flatCacheMiddleware middleware, I received the response in JSON, now when I test, it sends me an HTML. I am not too well versed with JS strict mode (planning to learn it soon), but I am sure the answer lies in the flatCacheMiddleware function.
So what do I modify in the flatCacheMiddleware function so it would send me JSON?
I manually added a new row to the products table for that customer and when I called the end point, it still showed me the old rows. So at what point do I clear the cache?
In a web app it would ideally be when the user logs out, but if I am using this as an api endpoint (or even on webapp there is no guarantee that the user will log out the traditional way), how do I determine if new records have been added and the cache needs to be cleared.
Appreciate the help. If there are any other node.js caching related suggestions you all can give, it would be truly helpful.
I found a solution to the issue by parsing the content to JSON format.
Change line:
res.send(cacheContent);
To:
res.send(JSON.parse(cacheContent));
I created cache 'brute force' invalidation method. Calling clear method will clear both cache file and data stored in memory. You have to call it after db change. You can also try delete specified key using cache.removeKey('key');.
function clear(req, res, next) {
try {
cache.destroy()
} catch (err) {
logger.error(`cache invalidation error ${JSON.stringify(err)}`);
res.status(500).json({
'message' : 'cache invalidation error',
'error' : JSON.stringify(err)
});
} finally {
res.status(200).json({'message' : 'cache invalidated'})
}
}
Notice, that calling the cache.save() function will remove other cached API function. Change it into cache.save(true) will 'prevent the removal of non visited keys' (like mentioned in comment in the flat-cache documentation.
I'm going to make web application (SPA) with:
Backend: Node.js (express)
Frontend: Jade + AngularJS
Database: Mongoose
I will send data (as a form) to backend in this way ExpressJS AngularJS POST (Check ANSWER)
It will be simple CRUD.
However i wondering how should I display data from backend?
For example:
I'll run application
var Partner = require('../model/partners');
router.get('/', function (req, res) {
Partner.find({}, function (err, partnerList) {
if (err) throw err;
res.render('campaign', {
partnerList: partnerList
});
});
});
And how should i display data (partnerList). Maybe in this way?
- each item in partnerList
= item.name
Or maybe there is another better way with angular to display data at view? I'm asking because later i'd like remove or update items from partnerList (CRUD operation). And it may be a problem because i will have to send item._id as a parameter to angular function?
For example if i will add button to remove record:
- each item in partnerList
= item.name
button(type='remove' ng-click="sub('#{item._id}')")
script.
app.controller('view1Ctrl', function($scope, $http) {
$scope.sub = function(id) {
$http.post('/',id).
success(function(data) {
console.log("posted successfully");
}).error(function(data) {
console.error("error in posting");
})
}
});
Probably it won't work correct
As said in previous coment, from my point of view I prefere to send the minimum required data from the backend to the client, but it depends of you infrastructure and you concurrent users.
Example 1:
You have a web app with +5K concurrent users, in this case is better handle all the huge stuff at frondend side or you will need to spend a lot of money in your backend hardware.
Practical case:
Users POST a new comment in a blog page. You sanitize the text string at the backend and put it at you preferred datastore... But JUST respond with a simple json like {"status": "ok"}. If the frond end recive this, modify the DOM with the text string that the client sent to the backend in the POST stage, but not send again all the HTML with this (for example) 500 characters comment.
If server responds with {"status":"error"}, modify the DOM to let the user know what's the problem about his comment (more specified json message {"status":"error", "data":"you comment is bigger than 500 chars"})
Problems:
You need extra frontend code to handle these situations in the client side. So this "maybe" will inpact on the user the 1st time that it visits your page.
Pros:
Less hardware costs
Overall less server response times.
More user interactive website modeling only certain parts of the DOM at any moment.
...
Example 2:
You have a simple page with low concurrent users. Then you choose. Let you backend to handle everything? Or keep working with json responses?
I always use the 1st example. Hope this helps in your question.
I think the preferred method would be to set up a second route from express to specifically render JSON, then use angular's $http method to get that data and use it in your controller. If you want to do it with a single route, you can pass the JSON data as a string to your view on the server-side, but it might get a little unruly.
// app.js
...
partnerList: JSON.stringify(partnerList);
...
// index.jade
div(ng-repeat="item in partnerList")
p {{ item.name }}
button(type='remove', ng-click="sub(item._id)")
...
script.
app.controller('view1Ctrl', function($scope, $http) {
$scope.partnerList = JSON.parse(#{partnerList});
...
EDIT To use the JSON string example, you would have to render using the Unbuffered Code syntax. But I'm not sure how you would do that inside a script. block. To instead go the route of serving JSON separately, change your server routes to this:
var Partner = require('../model/partners');
router.get('/', function (req, res) {
res.render('campaign');
});
router.get("/partner-list", function(req, res) {
Partner.find({}, function (err, partnerList) {
if (err) throw err;
res.json({ partnerList: partnerList });
});
});
Then your angular code will query that /partner-list path with $http.get().
script.
app.controller('view1Ctrl', function($scope, $http) {
$http.get("/partner-list").then(function(result) {
$scope.partnerList = result.data.partnerList;
});
...
});
I've got some data from a JSON file, which I use in my HTML getting it first from AngularJS like this:
$http.get('js/data.json').success(function(data) {
$scope.data = data;
});
And I want to update this JSON file after clicking a button in the HTML:
<button ng-click="postData(id)">Post</button>
You cannot write on files via JavaScript only (AngularJS).
You are to go via server side and point your "post" request to a server side script (i.e: PHP) and make that script do the job.
This sort of thing won't work. The file you are trying to write to would be on a server; and as it is right now, it would be a static resource. I'd suggest reading up on Angular resources, here. You can set up your server-side code to perform CRUD operations on the json file, but an actually database would be best. If you prefer to use a json format, Mongodb is your best choice; here is a link to Mongodb University, which offers free courses. I've done it in the past, and it's been great.
Now, for some actually help in your situation:
You can perform a GET request on your json file because it's seen as a static resource. The POST request, however, needs server-side scripting to do anything.
$http.get('api/YOUR_RESOURCE').success(function(data) {
$scope.database = data;
});
$http.post('api/YOUR_RESOURCE', {
data_key: data_value,
data_key2: data_value2
}).success(function(data) {
data[id].available = false;
});
This may be further ahead on your path to learning Angular, but here is a snippet of Node.js server code, with a Mongo database and Mongoose to handle the 'Schema', to help you get an idea of how this works:
var mongoose = require('mongoose'),
YOUR_RESOURCE = mongoose.model('YOUR_RESOURCE');
app.route('/api/YOUR_RESOURCE')
// This should be your GET request; 'api/
.get(
// Get all docs in resource
YOUR_RESOURCE.find().exec(function (err, data) {
if (err) {
return res.status(400).send({
message: SOME_ERROR_HANDLER
});
} else {
res.json(data); // return list of all docs found
}
});)
// Add new doc to database
.post(function (req, res) {
// The keys of the object sent from your Angular app should match
// those of the model
var your_resource = new YOUR_RESOURCE(req.body);
your_resource.save(function (err) {
if (err) {
return res.status(400).send({
message: SOME_ERROR_HANDLER
});
} else {
// returns newly created doc to Angular after successful save
res.json(your_resource);
}
});
);
Here is an SO page with a list of resources on getting started with Node; I recommend Node because of it's ease of use and the fact that it is written in JS. The Mongo University lessons also go through setting up you server for use with the database; you can choose between several flavors, such as Java, .NET, Python or Node.
There is a bit left out in the examples above, such as the Mongoose model and Node setup, but those will be covered in the resources I've linked to on the page, if you choose to read them. Hope this helps :)
Short here's the purpose of my application.
I have a PHP file reading data through an ODBC connection and writing them to a local database.
This PHP file needs to be run LOCAL ON THE SERVER each time a loop is processed in my node.js, socket.io server.
My setup is Apache, PHP 5.5.12 and node.js.
I was pretty convinced there was a simple way to this but I haven't had any luck getting Ajax or similar to work inside node.js by following other guides.
The code where the file should be processed inside looks like this.
var pollingLoop = function () {
// Update the local database
// HERE I WANT THE PHP FILE TO EXECUTE
// Make the database query
var query = connection.query('SOME LONG SQL QUERY IN HERE'),
status = []; // this array will contain the result of our db query
// set up the query listeners
query
.on('error', function(err) {
// Handle error, and 'end' event will be emitted after this as well
console.log( err );
updateSockets( err );
})
.on('result', function( runningstatus ) {
// it fills our array looping on each runningstatus row inside the db
status.push( runningstatus );
})
.on('end',function(){
// loop on itself only if there are sockets still connected
if(connectionsArray.length) {
pollingTimer = setTimeout(pollingLoop, POLLING_INTERVAL);
updateSockets({status:status});
}
});
};
Am I totally of track by trying to do that?
Try invoking php through the shell interface:
var exec = require("child_process").exec;
app.get('/', function(req, res){exec("php index.php", function (error, stdout, stderr) {res.send(stdout);});});
OR this link
I am developing a web application where the user can type in a "device id" on the web page (we have 100's of devices out on the field in production use each with a unique ID), that result entered by the user will be sent to the Node.js server that in return will store it into a variable and use it in a SQL Query to retrieve results about that particular device from the database server and then display the results back to the client web page.
Currently the form input feature has not been implemented yet even though I've already coded the form code in html.
The program works fine as it is if I were to manually change the DEVICE_ID to the device I wish to retrieve data from in the code but of course I want to be able to enter this on the client page instead of me having to change it in the server-side source code manually.
"use strict";
var pg = require('pg').native;
var http = require('http');
var $ = require('cheerio');
var fs = require('fs');
var url = require('url');
var htmlString = fs.readFileSync('index.html').toString();
var parsedHTML = $.load(htmlString);
var dbUrl = "tcp://URL HERE/";
// The Sign-ID
var DEVICE_ID = '2001202';
// Create the http server
http.createServer(function (request, response) {
var request = url.parse(request.url, true);
var action = request.pathname;
// Connect and query the database
pg.connect(dbUrl, function(err, client) {
// The complete sql query for everything that's needed for the app!
client.query("SQL QUERY IS HERE" + DEVICE_ID + "etc..",
function (err, result) {
// Remaining program code is here that performs DOM based
// manipulation to display results returned from the server
// to the client side page.
// Time to Render the document and output to the console
console.log(parsedHTML.html());
// Render the document and project onto browser
response.end(parsedHTML.html());
}
); // End client.query
}); // End pg.connect
}).listen(8080); // End http.CreateServer
pg.end();
I've considered the following:
1) Use An OnClick() function from within the HTML code, like this:
onclick="lookupSignID()
Then include an external JS file from within the HTML that includes the lookupSignID() function however I soon found out this is only performing client-side function and is not what I want.
2) AJAX is only good for if the server is generating new information by itself, therefore I can't use AJAX since the user is entering the device ID to get information from it.
3) Possibly using POST/ GET
Can anyone please advise on what course of action I should take? If solution (3) is the best way how would I go about doing this? Can it be integrated into my existed code (shown above) without many changes?
Thanks!
If you used jQuery on the client side with an AJAX POST function, and then on the server side, you have express.js, you could do this:
app.post('/deviceid', function(req, res) {
var deviceid = req.param('deviceid')
console.log(deviceid)
...
})