I have a NodeJS app running a websocket server using the ws npm package. In a callback from the message event ws.on("message", async (rawData, isBinary) => {}), I'm trying to update a document and then save it. The .find() method works fine, but the .save() method blocks execution completely.
const users = await Promise.all(
game.players.map((p) => User.findById(p.id)) // This works fine
);
// mess with users here
await Promise.all(users.map(u => u.save())) // <-- This doesn't work
await users[0].save() // <--- This doesn't work either
users[0].save((err, doc) => {
// This doesn't work either
})
users[0].save().then(doc => {
// console.log(doc) // <-- This doesn't work either
})
For starters, is this even possible ? Or am I thinking about it the wrong way and should I trigger some kind of POST request from the client to hit my http server instead to do the mongodb operations ? In any case, I'm struggling to understand why this is not possible.
Also something interesting is when I tried logging everything everywhere I tried to do the following
console.log(users[0].save())
users[0].save((err, doc) => {
if (err) console.log(err) // <-- no log here
console.log(doc) // <-- no log here
})
which threw mongoose's ParallelSaveError: Can't save() the same doc multiple times in parallel. So I'm guessing the action does take place but not entirely ?
Any insight on this is welcome.
I am currently working on a web app to manage an external database. I am not very familiar with express or NodeJS at this point so I wanted to ask how to send a JSON object to the client sides console without getting undefined?
I have this function to connect then select the what I need and afterwards I converted my JSON object to an array of JSON objects. It displays the data fine in the console as well.
async function connect() {
try {
await sequelize.authenticate();
console.log('Connection has been established successfully.');
} catch (err) {
console.error('Unable to connect to the database:', error);
}
info = await sequelize.query('select * from LeadsInformation', { type: QueryTypes.SELECT });
const details = JSON.stringify(info);
console.log(details);
detailsArray = JSON.parse(details);
console.log(detailsArray);
}
Everything works fine in here, I can get the data and display it in the terminal.
This is my GET route:
app.get("/list", (req, res) => {
connect();
res.json(detailsArray)
});
I have tried a couple of suggested ways based on other explanations and code snippets but none of them has worked so far so I left it like that. I thought foreaching through the data itself in the request would be a solution but it did not work. I also tried using the JSON itself and trying to display it and also tried using the body parser library. Though the library has not been updated for two years. Also I am using axios to fetch the data. It works fine when I try sending a simple string like "hello world" for example.
Is there anything that I'm missing or do you have any other solutions? I would also appreciate an explanation as well if possible.
Edit: It might also have to do something with how I am getting the response in the frontend. I'll look into that as well and will update this thread if I sort it out!
This is the way I get the response. I am currently trying to show in the console. I am using axios API.
Axios({
method: "GET",
url: "http://localhost:5000/list",
headers: {
"Content-Type": "application/json"
}
}).then(res => {
console.log(res.data.json);
});
Probably you have undefined in route because connect function doesn't return anything.
Also connect is an async function it means that it returns Promise and you have to call .then method or use await to get value from it.
Here is the code snippet with fixes that I described above.
async function connect() {
try {
await sequelize.authenticate();
console.log('Connection has been established successfully.');
} catch (err) {
console.error('Unable to connect to the database:', error);
}
info = await sequelize.query('select * from LeadsInformation', { type: QueryTypes.SELECT });
const details = JSON.stringify(info);
detailsArray = JSON.parse(details);
return detailsArray;
}
app.get("/list", async (req, res) => {
const result = await connect();
res.json(result)
});
Notice that in the router handler function I also use async and await because I call connect which is an asynchronous function.
The solution above did work and also another problem I had was that I wasn't getting the response correctly.
I ended up getting the response to the frontend after changing my code to the following from:
console.log(res.data.json);
To:
console.log(res.data[1]);
I've been having trouble with handling data from MongoDB using MongoJS where I have a promise that refuses to resolve. I am honestly confused why this does not work. It works completely fine on my local machine but once I move it to my server it breaks. Except it only breaks as a module. Is it because I'm using deasync? If it is, how do I fix it?
Here's what I'm doing compressed down to what doesn't work for me
In the index:
const db = require('./db')
//Obviously this works I'm just showing what I mean by "module"
data = db.get('somedata') //Passthrough for getData
console.log(data)
//On local machine, console says: thedata
//On deb server, console says: Promise { 'thedata' }
//On deb server, console ALSO says: MongoDB request timed out: Promise { 'thedata' }
// ^ (this is from the timeout part I added because it froze)
In the DB module:
const db = mongojs(`connectionURIstring`, ['bot'])
const bdata = db.bot
function syncP(promise) {
var answer;
promise.then(value => {
//Runs every time on local machine but not on server as module
answer = value
})
//I also have .catch but it's not relevant
setTimeout(function () {
//Never runs on local machine but runs every time on server as module
if (answer) return;
answer = promise
console.error('MongoDB request timed out:', promise)
}, 2000)
require('deasync').loopWhile(function () { return !answer })
return answer
}
function getData(datapath) {
//Datapath processing here
var GDP = new Promise((resolve, reject) => {
bdata.findOne({
_id: primary
}, function (err, dataJ) {
//Stuff where I format data, comes out as variable data
resolve(data)
})
})
return syncP(GDP)
}
I genuinely don't know why this doesn't work. There's no reason it shouldn't work as a module if it works independently. It works on another computer. The only thing I can assume is that it's something to do with how deasync works, but even then, there's no reason why that would interfere with the promise, as it's separate from the promise itself.
This is driving me insane.
I want to test the saveRecords function for the failure and before that, I have to authenticate and connect the MongoDB. This is the code.
before(() => {
sinon.stub(Authentication, 'authenticate').returns(true);
sinon.stub(mongodb, 'connect').resolves("connected");
sinon.stub(models, 'saveRecords').throws(new Error("Error while saving record"));
});
it('Should error out if record is not inserted into the mongodb
collection', () => {
orderWebhook(req, res)
expect(res.result).to.contain("Error while saving record");
});
Here is the code I am testing.
exports.orderWebhook = async (req, res) => {
try {
const isAuthenticated = Authentication.authenticate(req);
if (isAuthenticated) {
await mongodb.connect();
await models.saveRecords(req.body");
res.status(200).send('Saved Successfully!');
} else {
res.status(403).send('Error! Auth failed!');
}
} catch (error) {
res.status(400).send(error.message);
}
}
I am assuming that this code will stub the authenticate then connect MongoDB and then try to insert the record and throw the error. But it is running two times when I debug with the VSCode debugger.
The first time it is returning true for the authenticate function and not resolving the MongoDB connect and return to expect immediately.
The second time it is running all three properly and throwing the expected error.
It is failing when I run the test in the terminal, What could be the issue?
Update: I noticed that the problem is related to the promise. Sinon is resolving the request and I am using await mongodb.connect(); but it is not working as expected, and if I remove await and return value instead of promise then it works.
My stack is node, express and the pg module. I really try to understand by the documentation and some outdated tutorials. I dont know when and how to disconnect and to end a client.
For some routes I decided to use a pool. This is my code
const pool = new pg.Pool({
user: 'pooluser',host: 'localhost',database: 'mydb',password: 'pooluser',port: 5432});
pool.on('error', (err, client) => {
console.log('error ', err); process.exit(-1);
});
app.get('/', (req, res)=>{
pool.connect()
.then(client => {
return client.query('select ....')
.then(resolved => {
client.release();
console.log(resolved.rows);
})
.catch(e => {
client.release();
console.log('error', e);
})
pool.end();
})
});
In the routes of the CMS, I use client instead of pool that has different db privileges than the pool.
const client = new pg.Client({
user: 'clientuser',host: 'localhost',database: 'mydb',password: 'clientuser',port: 5432});
client.connect();
const signup = (user) => {
return new Promise((resolved, rejeted)=>{
getUser(user.email)
.then(getUserRes => {
if (!getUserRes) {
return resolved(false);
}
client.query('insert into user(username, password) values ($1,$2)',[user.username,user.password])
.then(queryRes => {
client.end();
resolved(true);
})
.catch(queryError => {
client.end();
rejeted('username already used');
});
})
.catch(getUserError => {
return rejeted('error');
});
})
};
const getUser = (username) => {
return new Promise((resolved, rejeted)=>{
client.query('select username from user WHERE username= $1',[username])
.then(res => {
client.end();
if (res.rows.length == 0) {
return resolved(true);
}
resolved(false);
})
.catch(e => {
client.end();
console.error('error ', e);
});
})
}
In this case if I get a username already used and try to re-post with another username, the query of the getUser never starts and the page hangs. If I remove the client.end(); from both functions, it will work.
I am confused, so please advice on how and when to disconnect and to completely end a pool or a client. Any hint or explanation or tutorial will be appreciated.
Thank you
First, from the pg documentation*:
const { Pool } = require('pg')
const pool = new Pool()
// the pool with emit an error on behalf of any idle clients
// it contains if a backend error or network partition happens
pool.on('error', (err, client) => {
console.error('Unexpected error on idle client', err) // your callback here
process.exit(-1)
})
// promise - checkout a client
pool.connect()
.then(client => {
return client.query('SELECT * FROM users WHERE id = $1', [1]) // your query string here
.then(res => {
client.release()
console.log(res.rows[0]) // your callback here
})
.catch(e => {
client.release()
console.log(err.stack) // your callback here
})
})
This code/construct is suficient/made to get your pool working, providing the your thing here things. If you shut down your application, the connection will hang normaly, since the pool is created well, exactly not to hang, even if it does provides a manual way of hanging,
see last section of the article.
Also look at the previous red section which says "You must always return the client..." to accept
the mandatory client.release() instruction
before accesing argument.
you scope/closure client within your callbacks.
Then, from the pg.client documentation*:
Plain text query with a promise
const { Client } = require('pg').Client
const client = new Client()
client.connect()
client.query('SELECT NOW()') // your query string here
.then(result => console.log(result)) // your callback here
.catch(e => console.error(e.stack)) // your callback here
.then(() => client.end())
seems to me the clearest syntax:
you end the client whatever the results.
you access the result before ending the client.
you don´t scope/closure the client within your callbacks
It is this sort of oposition between the two syntaxes that may be confusing at first sight, but there is no magic in there, it is implementation construction syntax.
Focus on your callbacks and queries, not on those constructs, just pick up the most elegant for your eyes and feed it with your code.
*I added the comments // your xxx here for clarity
You shouldn't disconnect the pool on every query, connection pool is supposed to be used to have "hot" connections.
I usually have a global connection on startup and the pool connection close on (if) application stop; you just have to release the connection from pool every time the query ends, as you already do, and use the same pool also in the signup function.
Sometimes I need to preserve connections, I use a wrapper to the query function that checks if the connection is active or not before perform the query, but it's just an optimization.
In case you don't want to manage open/close connections/pool or release, you could try https://github.com/vitaly-t/pg-promise, it manage all that stuff silently and it works well.
The documentation over node-postgres's github says:
pro tip: unless you need to run a transaction (which requires a single client for multiple queries) or you have some other edge case like streaming rows or using a cursor you should almost always just use pool.query. Its easy, it does the right thing ™️, and wont ever forget to return clients back to the pool after the query is done.
So for non-transactional query, calling below code is enough.
var pool = new Pool()
pool.query('select username from user WHERE username= $1',[username], function(err, res) {
console.log(res.rows[0].username)
})
By using pool.query, the library will take care of releasing the client after the query is done.
Its quite simple, a client-connection (single connection) opens up, query with it, once you are done you end it.
The pool concept is different, in the case of mysql : you have to .release() the connection back to the pool once you are done with it, but it seems that with pg is a different story:
From an issue on the github repo : Cannot use a pool after calling end on the pool #1635
"Cannot use a pool after calling end on the pool"
You can't reuse a pool after it has been closed (i.e. after calling
the .end() function). You would need to recreate the pool and discard
the old one.
The simplest way to deal with pooling in a Lambda is to not do it at
all. Have your database interactions create their own connections and
close them when they're done. You can't maintain a pool across
freeze/thaw cycles anyway as the underlying TCP sockets would be
closed.
If opening/closing the connections becomes a performance issue then
look into setting up an external pool like pgbouncer.
So I would say that your best option is to not end the pool, unless you are shutting down the server