nodejs chat example does not work - mongodb

I've come across a node chat example on github, When I try to run it, I see the following error:
Error connecting to mongo perhaps it isn't running ?
I've installed mongo 0.9.2, nodejs 5.2 pre, npm 3.0 and other dependencies. The example can be found here: https://github.com/gregstewart/chat.io
I can not determine whether if the example not really works or I didn't run it right. Please help.

Did you install and start mongo-db on your system? This error is mostly because of a missing mongo instance running on the local machine.
Check out the follwing code excerpts from chat.io.
main.js:
/**
* Configure the user provider (mongodB connection for user data storage)
*/
var userProvider = new UserProvider('localhost', 27017);
Creates a new UserProvider object using host and port for database (localhost:27017, mongo-db default).
UserProvider.js:
UserProvider = function(host, port) {
this.db = new mongo.Db('node-mongo-chat', new Server(host, port, {auto_reconnect: true}, {}));
this.db.addListener('error', function(error) {
console.log('Error connecting to mongo -- perhaps it isn\'t running?');
});
this.db.open(function() {
});
};
Opening the connection to the server, printing out an error on failure (the error you mentioned above).
Consider reading up on the mongo-db docs concerning installation and setup here

Related

NextJs + Mongoose + Mongo Atlas multiple connections even with caching

I am using NextJS to build an app. I am using MongoDB via mongoosejs to connect to my database hosted in mongoAtlas.
My database connection file looks like below
import mongoose from "mongoose";
const MONGO_URI =
process.env.NODE_ENV === "development"
? process.env.MONGO_URI_DEVELOPMENT
: process.env.MONGO_URI_PRODUCTION;
console.log(`Connecting to ${MONGO_URI}`);
const database_connection = async () => {
if (global.connection?.isConnected) {
console.log("reusing database connection")
return;
}
const database = await mongoose.connect(MONGO_URI, {
authSource: "admin",
useNewUrlParser: true
});
global.connection = { isConnected: database.connections[0].readyState }
console.log("new database connection created")
};
export default database_connection;
I have seen this MongoDB developer community thread and this GitHub thread.
The problem seems to happen only in dev mode(when you run yarn run dev). In the production version hosted on Vercel there seems to be no issue. I understand that in dev mode the server is restarted every time a change is saved so to cache a connection you need to use as global variable. As you can see above, I have done exactly that. The server even logs: reusing database connection, then in mongoAtlas it shows like 10 more connections opened.
How can I solve this issue or what am I doing wrong?

connecting to mongodb replicaSet with nestjs and typeorm is not working

problem
I'm trying to connect to mongodb with nestjs(^8.2.3) and typeorm(^0.2.28)
In test environment, connecting to mongodb standalone server is working. For your information, node mongodb library version is ^3.6.2.
production sample code(nestjs server)
I referred the typeorm code to write mongodb options
import { TypeOrmModule } from '#nestjs/typeorm';
import { MongoConnectionOptions } from 'typeorm/driver/mongodb/MongoConnectionOptions';
export const configForOrmModule = TypeOrmModule.forRootAsync({
imports: [],
useFactory: async () => {
const mongodbConfig: MongoConnectionOptions = {
type: 'mongodb',
username,
// for replicaSet (production)
hostReplicaSet: 'server1.example.com:20723,server2.example.com:20723,server.example.com:20723',
replicaSet: 'replicaSetName'
port: Number(port),
password: encodeURIComponent(password),
database,
authSource,
synchronize: true,
useUnifiedTopology: true,
entities: [Something],
};
return mongodbConfig;
},
inject: [],
});
But in production environment, when nestjs server try to connect to mongodb replicaSet, the server get this server selection loop error message over and over again like below. Interesting thing was the domain that the server tried to connect was different from replicaSet hosts(ex. another-hostname not included in server1.example.com:20723,server2.example.com:20723,server.example.com:20723). (+ edited: the another hostname is actual physical server indicated by the dns(server.example.com))
[39m01/28/2022, 2:39:16 AM [31m ERROR[39m [38;5;3m[TypeOrmModule] [39m[31mUnable to connect to the database. Retrying (3)...[39m
MongoServerSelectionError: getaddrinfo ENOTFOUND <another-hostname>
at Timeout._onTimeout (/home/node/app/node_modules/mongodb/lib/core/sdam/topology.js:430:30)
at listOnTimeout (node:internal/timers:557:17)
at processTimers (node:internal/timers:500:7)
what I’ve tried but these not worked
remove useUnifiedTopology: true option
downgrade mongodb library version to 3.5.11 (I've read in mongodb community there are something bug with topology after 3.6 version)
use host option not the hostReplicaSet
if you need more information, please tell me. thank you for your helping.
It was kubernates DNS issue. The hostReplicaSet server1.example.com:20723,... is resolved to host1 (physical server name. without example.com) but, k8s doesn't know it. so connection was failed.
there are two options
update kubernates /etc/hosts setting to add host1 -> host1.example.com
or update mongodb hostname host1 -> host1.example.com

Debugging connection PostgreSQL Loopback 4

Im on a mac(OS 10.14) using nodejs 14 and PostgresSQL 12.
I just installed Loopback4 and after following this tutorial Im not able to use any of the enpoints that use Models, ie that connect to Postgres, I constantly get a timeout.
It seems like its not even reaching the Postgres Server, but the error gives no information, just that the request times out.
There are no issues with the Postgres server since I can connect and request information with other nodejs applications to the same database.
I also tried to set this as the host host: '/var/run/postgresql/', same result.
I now tried the approach with a Docker container, setting the datasource files as follows:
import {inject, lifeCycleObserver, LifeCycleObserver} from '#loopback/core';
import {juggler} from '#loopback/repository';
const config = {
name: 'mydb',
connector: 'postgresql',
url: 'postgres://postgres:mysecretpassword#localhost:5434/test',
ssl: false,
};
// Observe application's life cycle to disconnect the datasource when
// application is stopped. This allows the application to be shut down
// gracefully. The `stop()` method is inherited from `juggler.DataSource`.
// Learn more at https://loopback.io/doc/en/lb4/Life-cycle.html
#lifeCycleObserver('datasource')
export class PostgresSqlDataSource extends juggler.DataSource
implements LifeCycleObserver {
static dataSourceName = 'PostgresSQL';
static readonly defaultConfig = config;
constructor(
#inject('datasources.config.PostgresSQL', {optional: true})
dsConfig: object = config,
) {
super(dsConfig);
}
}
With that same url I can log on my command line from my mac.
Is there a way to add logging and print any connection error? Other ways to debug it?
[UPDATE]
As of today Loopback4 Postgres connector does not work properly with Nodejs 14.
When starting the application, instead of running
npm start, you can set the debug string by running:
DEBUG=loopback:connector:postgresql npm start
If you want it to be more generic, you can use:
DEBUG=loopback:* npm start

Can not connect Azure Functions to MongoDB (created in azure)

I have a MongoDB setup on azure, and I am tring to connect to it via azure function.
These are the steps I took:
Creating a Simple Azure Function
Installed the MongoDB Driver on Azure, To install the MongoDB Node.js driver, I went go to .scm.azurewebsites.net, and clicked on 'Debug Console' -> 'PowerShell'.
I Navigated to the D:\home\site\wwwroot directory and clicked on the plus icon to create a new file called package.json.
I Created and saved the below package.json file.
{
"name": "nameofunction",
"dependencies": {
"mongodb": "3.x"
}
}
Next, I ran npm install from the shell.
From the Azure Function I should be able to connect to MongoDB and execute a query using the below code.
const mongodb = require('mongodb');
const url = "mongodb://cosmod: <PASSWORD>==#cosmodb.documents.azure.com:10255/?ssl=true&replicaSet=globaldb";
module.exports = async function (context, req) {
mongodb.connect(url, function(error, client) {
if (error) throw error;
var dbo = client.db("mydb");
dbo.createCollection("customers", function(err, res) {
if (err) throw err;
context.log("Collection created!");
db.close();
});
});
};
My code is throwing up a Status: 500 Internal Server Error
The more I look at the code, the more i can not understand why this should not work.
The package-lock.jsonhas all the dependencies loaded after I ran npm install in the shell.
I appreciate any help in resolving this.
This seems weired, I also followed same and was able to connect to my db.
Can you please check your cosmos connectiondb, mongo compatible connection string? Are you able to connect that from other mongo clients
Status: 500 Internal Server Error
I assume that it dues to the code mongodb.connect(url, function(error, client)
please change the code to
mongodb.MongoClient.connect(uri, function(error, client)
A review of the Azure Cosmos DB account- Quick start documentation accessible via the Azure Cosmos DB account menu side blade; connecting the MongoDB app is among others via:
the Node.js 2.2 driver and
the Node.js 3.0 driver
I was using the Node.js 2.2 driver connection string in the azure function which is not compatible with the Node.js 3+ driver dependency in my app. Using the Node.js 3.0 driver connection string, I was able to connect the MongoDB app, without the error. The double equality sign in the password string is url encoded in the 3+ driver.
Node.js 3+ driver connection string
var mongoClient = require("mongodb").MongoClient;
mongoClient.connect("mongodb://cosmodb:<PWD>%3D%3D#cosmodb.documents.azure.com:10255/?ssl=true", function (err, client) {
client.close();
});
Node.js 2.2 driver connection string
var mongoClient = require("mongodb").MongoClient;
mongoClient.connect("mongodb://cosmodb:<PWD>==#cosmodb.documents.azure.com:10255/?ssl=true", function (err, db) {
db.close();
});

nodejs/mongoose: connect to db that's using replica sets

i have installed mongodb (1.8.3) on two seperate servers and set them up to use "replica sets" as found here: http://www.mongodb.org/display/DOCS/Replica+Set+Tutorial
everything looks good so far: one server is recognized as primary, one as secondary (when i access them via commandline).
the problem is that i can't connect to the DB using node.js (0.4.10) and mongoose (2.1.0) like this:
var mongo = require('mongoose');
mongo.connectSet('mongodb://host/dbname,mongodb://host2/dbname');
i always get the following error message:
TypeError: Cannot read property 'reconnectWait' of undefined
at new <anonymous> (/var/www/node/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connections/repl_set_servers.js:23:31)
at NativeConnection.doOpenSet (/var/www/node/node_modules/mongoose/lib/drivers/node-mongodb-native/connection.js:80:18)
at NativeConnection.openSet (/var/www/node/node_modules/mongoose/lib/connection.js:252:8)
at Mongoose.connectSet (/var/www/node/node_modules/mongoose/lib/index.js:116:27)
...
searched around a bit and found a post somewhere saying that i also have to supply the name of the replica set - so i tried this instead:
mongo.connectSet('mongodb://host/dbname,mongodb://host2/dbname', rs_name:"name_replicaset"});
what am i doing wrong here ...?!
ok, there was an error in the https://github.com/christkv/node-mongodb-native module. it's fixed now but not yet pushed to NPM. so for all you guys getting the same error, here is the fix:
https://github.com/christkv/node-mongodb-native/pull/340
after that, you can just say
var mongo = require('mongoose');
mongo.connectSet('mongodb://host:27018/testdb, host2:27017/testdb, host3:27019/testdb', function (err) {
if (err) {
console.log("could not connect to DB: " + err);
}
});
mongo.connection.on('open', function () {
console.log("mongodb connection open");
}