I am trying to develop a MERN stack application, and I have done numerous attempts at this. So, what I am trying to achieve is have some data I am pulling from an api and dump it to a database, then query from the database to create a JSON file every 5 minutes(using jenkins and python, the best approach I can think of). Below is a method I am implementing and it does not work. If I remove the setInterval() function and un-comment the callback function, the code works but does not update the data.
const express = require('express');
const fs = require('fs');
const app = express();
// Read JSON File
function readJSON(callback) {
fs.readFile('./name.json', "utf8", function(err, result) {
if (err) callback (err);
callback(JSON.parse(result));
});
}
// Process JSON File during callback
// readJSON(function(res) {
// app.get('/api/customers', (request, response) => {
// response.json(res);
// });
// });
// Attempt to run every 5 minutes
setInterval(readJSON(function(res) {
app.get('/api/customers', (request, response) => {
response.json(res);
})}, 60000 * 5); // 5 Minutes
const port = 5000
app.listen(port, () => `Server running on port ${port}`);
I thought of using sockets, but I don't want it to be real-time, only live data on an interval. Restful API's I don't believe are a good fit here either, I don't want a 2-way communication to modify/update the data. If my approach is bad, please let me know why you'd pick another approach. I am just trying to establish a foundation in full-stack web dev. Thanks!
A logical code would be:
On server side:
function readJSON(callback) {
fs.readFile('./name.json', "utf8", function(err, result) {
if (err) callback(err);
callback(null, JSON.parse(result));
});
}
app.get('/api/customers', (request, response) => {
readJSON((err, nameContent) => {
if(err) {
response.status(500).send(err);
}
response.send(nameContent);
})
});
And in the client side ask for the data every 5 minutes:
someAjaxMethod('/api/customers', (err, nameContent) => console.log(err, nameContent));
Related
I was learning to build a weather app using Node (Express) + React. I successfully fetched weather data from open weather API.
However I was directly using the open weather API key in my React app like this const weatherURL = 'http://api.openweathermap.org/data/2.5/weather?q=london,uk&APPID=1234567qwerty';. Obviously this is not safe as it exposed the API key to the client. I thought about storing the API key in .env file, but according to [this answer][1], I should never store API key in .env file or .gitignore. The right way is to make a request to backend API and make an API call to backend and send the data back. I could not find out how to do it. Can anyone help?
Following is my node js code:
const express = require('express');
const cors = require('cors');
const app = express();
const SELECT_ALL_QUERY = 'SELECT * FROM `mySchema`.`myTable`;';
app.use(cors());
app.get('/', (req, res) => {
res.send('go to /myTable to see content')
});
const pool = require('./awsPool');
pool.getConnection((err, connection) => {
if (err) {
return console.log('ERROR! ', err);
}
if(!connection) {
return console.log('No connection was found');
}
app.get('/myTable', (req, res) => {
console.log(connection);
connection.query(SELECT_ALL_QUERY, (err, results) => {
if (err) {
return res.send(err)
}
else {
return res.json({
data: results
})
};
});
});
});
let port=process.env.PORT||4000;
app.listen(port, () => {
console.log(`App running on port ${port} `);
});```
[1]: https://stackoverflow.com/a/57103663/8720421
What the linked answer was suggesting is to create a route in your Node/Express backend API that will make the call to the weather API for you, instead of the front end. This way the request and your API key are not public-facing whenever your front end makes a call.
The method for doing this would essentially be the same as what you have done in React, making an HTTP request using a built-in or 3rd party library. This resource I just found has some information on how to do both.
The simplest pure http-request in node looks like this:
const http = require('http')
const url = 'http://api.openweathermap.org/data/'
http.request(url, callback).end()
function callback (weatherResponse) {
let jsonString = ''
weatherResponse.on('data', chunk => {
jsonString += chunk
})
weatherResponse.on('end', () => {
// Now you have the complete response and can do whatever you want with it
// like return it to your user `res.send(jsonString)`
console.log(jsonString)
})
}
Many people find it bulky to having to handle chunks and the whole asynchronous thing, so there are many popular npm modules, like: https://www.npmjs.com/package/axios. (And here's a list of other contenders https://github.com/request/request/issues/3143).
Also, it is normal to store API-keys in environment variables on the backend. It makes things easy if you ever try to dockerize your app, or just scale up to using two backend servers instead of one.
I found a solution based on #ippi answer, add the following part to the original code:
const request = require('request');
const url = 'http://api.openweathermap.org/data/2.5/weather?q=london,uk&APPID=1234567';
app.get('/weather', (req, res) => {
request(url, (error, response, body) => {
if (!error && response.statusCode == 200) {
var info = JSON.parse(body)
res.send(info);
}
})
})
The url can be stored in .env file and passed into the above code. The returned weather data can be viewed in JSON format at http://localhost:4000/weather. In React the weather data can be fetched via this localhost url.
EDIT: request is deprecated, so here is a solution using axios
app.get('/weather', (req, res) => {
axios.get(url)
.then(response => {res.json(response.data)})
.catch(error => {
console.log(error);
});
})
User Passport middleware for nodeJs/Express. They provide passport-headerapikey strategy using which you can create and authorize apiKeys. http://www.passportjs.org/packages/passport-headerapikey/
I'm using the request library in Node.js to do a https request to get data from another service. This is called asynchronously, right? So my code keeps running before all of the data is there, correct?
My problem is that the data is needed right afterwards to calculate some things. My code throws an error during that calculation because the data from the service is undefined...
Could it be possible that the data is just not there yet? And if so, what do you do against that?
Here is a copy of the request:
const request = require('request');
request(someUrl, {"Accept": "application/json"}, (err, res, body) => {
if (err)
handleError(err);
body = JSON.parse(body);
return body;
});
This kind of situation is pretty common in react/angular/vue kinda web apps, sometimes you need the data right away. But it is not available then, after a Rest call or something it becomes available.
So, the simplest solution?
Just add a check, for example:
const calculate = (someVal)=>{
if(!someVal) return ;
//otherwise do the calculation
}
There are plenty of other ways, by mostly making the calculation async. For your function, you can do this
const promOp = function(){
return new Promise((resolve, reject) => {
request(someUrl, {"Accept": "application/json"}, (err, res, body) => {
if (err) reject(err);
body = JSON.parse(body);
resolve(body);
});
}
}
//then
promOp()
.then((body)=>{
//calculate here
})
//or can use the `Async/Await` syntax instead of then
const op = async () => {
const body = await promOp;
//calculate here
}
I'm trying to set up HTTP2 for an Express app I've built. As I understand, Express does not support the NPM http2 module, so I'm using SPDY. Here's how I'm thinking to go about it-I'd appreciate advice from people who've implemented something similar.
1) Server setup-I want to wrap my existing app with SPDY, to keep existing routes. Options are just an object with a key and a cert for SSL.
const app = express();
...all existing Express stuff, followed by:
spdy
.createServer(options, app)
.listen(CONFIG.port, (error) => {
if (error) {
console.error(error);
return process.exit(1)
} else {
console.log('Listening on port: ' + port + '.')
}
});
2) At this point, I want to enhance some of my existing routes with a conditional PUSH response. I want to check to see if there are any updates for the client making a request to the route (the client is called an endpoint, and the updates are an array of JSON objects called endpoint changes,) and if so, push to the client.
My idea is that I will write a function which takes res as one of its parameters, save the endpoint changes as a file (I haven't found a way to push non-file data,) and then add them to a push stream, then delete the file. Is this the right approach? I also notice that there is a second parameter that the stream takes, which is a req/res object-am I formatting it properly here?
const checkUpdates = async (obj, res) => {
if(res.push){
const endpointChanges = await updateEndpoint(obj).endpointChanges;
if (endpointChanges) {
const changePath = `../../cache/endpoint-updates${new Date().toISOString()}.json`;
const savedChanges = await jsonfile(changePath, endpointChanges);
if (savedChanges) {
let stream = res.push(changePath, {req: {'accept': '**/*'}, res: {'content-type': 'application/json'}});
stream.on('error', function (err) {
console.log(err);
});
stream.end();
res.end();
fs.unlinkSync(changePath);
}
}
}
};
3) Then, within my routes, I want to call the checkUpdates method with the relevant parameters, like this:
router.get('/somePath', async (req, res) => {
await checkUpdates({someInfo}, res);
ReS(res, {
message: 'keepalive succeeded'
}, 200);
}
);
Is this the right way to implement HTTP2?
First of all, this is one of my first projects in Node.js so I'm very new to it.
I have a project I want to make that is a SOAP (I know, SOAP... backwards compatibility, huh?) interface that connects to an Oracle database.
So I have a WSDL describing what these functions look like (validation for addresses and stuff) and I have a connection to the database.
Now when using the SOAP npm module, you need to create a server and listen using a service that allows you to respond to requests. I have a separate file that contains my SOAP service but this service should do queries on the database to get its results.
How would I go about sort of 'injecting' my database service into my SOAP service so that whenever a SOAP call is done, it orchestrates this to the correct method in my database service?
This is what my code looks like:
databaseconnection.js
var oracledb = require('oracledb');
var dbConfig = require('../../config/development');
var setup = exports.setup = (callback) => {
oracledb.createPool (
{
user : dbConfig.user,
password : dbConfig.password,
connectString : dbConfig.connectString
},
function(err, pool)
{
if (err) { console.error(err.message); return; }
pool.getConnection (
function(err, connection)
{
if (err) {
console.error(err.message);
return callback(null);
}
return callback(connection);
}
);
}
);
};
databaseservice.js
var DatabaseService = function (connection) {
this.database = connection;
};
function doSomething(callback) {
if (!this.database) { console.log('Database not available.'); return; }
this.database.execute('SELECT * FROM HELP', function(err, result) {
callback(result);
});
};
module.exports = {
DatabaseService: DatabaseService,
doSomething: doSomething
};
soapservice.js
var myService = {
CVService: {
CVServicePort: {
countryvalidation: function (args, cb, soapHeader) {
console.log('Validating Country');
cb({
name: args
});
}
}
}
};
server.js
app.use(bodyParser.raw({type: function(){return true;}, limit: '5mb'}));
app.listen(8001, function(){
databaseconnection.setup((callback) => {
var temp = databaseservice.DatabaseService(callback);
soapservice.Init(temp);
var server = soap.listen(app, '/soapapi/*', soapservice.myService, xml);
databaseservice.doSomething((result) => {
console.log(result.rows.length, ' results.');
});
});
console.log('Server started');
});
How would I go about adding the databaseservice.doSomething() to the countryvalidation soap method instead of 'name: args'?
Also: I feel like the structure of my code is very, very messy. I tried finding some good examples on how to structure the code online but as for services and database connections + combining them, I didn't find much. Any comments on this structure are very welcome. I'm here to learn, after all.
Thank you
Dieter
The first thing I see that looks a little off is the databaseconnection.js. It should be creating the pool, but that's it. Generally speaking, a connection should be obtained from the pool when a request comes in and release when you're done using it to service that request.
Have a look at this post: https://jsao.io/2015/02/real-time-data-with-node-js-socket-io-and-oracle-database/ There are some sample apps you could have a look at that might help. Between the two demos, the "employees-cqn-demo" app is better organized.
Keep in mind that the post is a little dated now, we've made enhancements to the driver that make it easier to use now. It's on my list to do a post on how to build a RESTful API with Node.js and Oracle Database but I haven't had a chance to do it yet.
I'm trying to create a basic app in node.js that a) tracks a keyword in twitter and temporarily stores messages relating to that keyword, b) after enough messages have been accumulated, return it to the user. I'm using the ntwitter library.
I've a basic long polling system implemented on my client and server side, but I'm having some trouble on verification. The way I set it up currently, it verifies the user each time /api/streamfeed is called, so potentially every 30sec (since I have a 30s timeout schedule) before checking the stream. I'm thinking this will get me into trouble since I believe verification is rate-limited? Is there a way to check whether I'm verified without having to ping Twitter's API (perhaps store a boolean after the first attempt)?
Client side:
//upon receiving a response, poll again
function getStreamFeed() {
console.log('calling getStreamFeed');
$http.get('/api/streamfeed').success(function(data) {
console.log(data)
getStreamFeed();
});
};
setTimeout(getStreamFeed, 1000);
Server side:
app.get('/api/streamfeed', function(req, res) {
/*
...
polling code
...
*/
twit.verifyCredentials(function(err, data) {
if (err) res.send(404);
twit.stream('statuses/filter', {
track: 'justin bieber'
}, function(stream) {
stream.on('data', function(data) {
console.log(data.text)
messages.push(data.text);
});
})
});
});
I'd send the credentials back and resend them again... this could be a bool, or actual credentials to use. these aren't your private keys or anything, only the user's.
could also be sent in headers and cookies and properly hashed etc.
this just simply shows a pattern that should work.
client side:
function getStreamFeed(credentials) {
//upon receiving a response, poll again
console.log('calling getStreamFeed');
var url = '/api/streamfeed';
if (credentials) {
url += '&credentials=' + credentials;
}
$http
.get(url)
.success(function(data) {
console.log(data)
getStreamFeed(true);
});
};
setTimeout(getStreamFeed, 1000);
Server side:
app.get('/api/streamfeed', function(req, res) {
function twitStream () {
twit.stream('statuses/filter', {track: 'justin bieber'}, function(stream) {
stream.on('data', function(data) {
console.log(data.text)
messages.push(data.text);
});
}
}
var credentials = req.query.credentials;
if (credentials) {
twitStream()
}
twit.verifyCredentials(function(err, data) {
if (err) res.send(404);
twitStream()
});
});