Mongodb Connections

MongoDB Connection

Introduction

In this tutorial, we will discuss various ways to connect to MongoDB.

Starting the MongoDB Service

In previous tutorials, we have discussed how to start the MongoDB service. You just need to execute **mongod** in the bin directory of your MongoDB installation folder. After executing the startup command, MongoDB will output some necessary information and then stop showing any further output. It will then wait for incoming connections. Once a connection is established, it will begin printing log information. You can use the MongoDB shell to connect to the MongoDB server. You can also connect using PHP. In this tutorial, we will use the MongoDB shell to connect to the MongoDB service. In subsequent chapters, we will cover how to connect to MongoDB using PHP, Python, and Node.js.

Standard URI Connection Syntax:

mongodb://[username:password@]host1[:port1][,...hostN[:portN]][/[?options]]

mongodb://: Protocol header indicating MongoDB usage.
[username:password@]: (Optional) Authentication credentials including username and password.
host1[:port1][,...hostN[:portN]]: Server address and port(s), which can be one or multiple MongoDB server addresses and ports.
: (Optional) Default authentication database.
[?options]: (Optional) Connection options.

The standard connection format includes several options, as shown below:

authSource: Specifies the authentication database.
replicaSet: Specifies the replica set name.
ssl: Enables SSL connection (true or false).
readPreference: Specifies read preference, such as primary, primaryPreferred, secondary, secondaryPreferred, nearest.
connectTimeoutMS: Specifies connection timeout in milliseconds.
socketTimeoutMS: Specifies socket timeout in milliseconds.

Connecting to a Local MongoDB Instance (Default Port 27017)

mongodb://localhost

Connecting to a Local MongoDB Instance with Database Specified

mongodb://localhost/mydatabase

Connecting to a Local MongoDB Instance Using Username and Password

mongodb://username:password@localhost/mydatabase

Connecting to a Remote MongoDB Instance

mongodb://remotehost:27017

Connecting to a Replica Set

mongodb://host1:27017,host2:27017,host3:27017/mydatabase?replicaSet=myReplicaSet

Connecting to MongoDB Using SSL

mongodb://username:password@localhost:27017/mydatabase?ssl=true

Connecting with Multiple Options

mongodb://username:password@localhost:27017/mydatabase?authSource=admin&ssl=true

Python (PyMongo)

Example

from pymongo import MongoClient

client = MongoClient('mongodb://user:password@localhost:27017/mydatabase?authSource=admin')

db = client['mydatabase']

Node.js (Mongoose)

Example

const mongoose = require('mongoose');

mongoose.connect('mongodb://user:password@localhost:27017/mydatabase?authSource=admin', {
  useNewUrlParser: true,
  useUnifiedTopology: true
});

const db = mongoose.connection;

db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function () {
  console.log('Connected to MongoDB');
});

PHP (MongoDB Driver)

Example

<?php

require 'vendor/autoload.php'; // Include Composer autoloader file

$client = new MongoDBClient("mongodb://localhost:27017"); // Connect to local MongoDB instance

$database = $client->selectDatabase('mydatabase'); // Select database

$collection = $database->selectCollection('mycollection'); // Select collection

// Insert document
$result = $collection->insertOne(['name' => 'Alice', 'age' => 30]);

echo "Inserted with Object ID '{$result->getInsertedId()}'";

// Query document
$document = $collection->findOne(['name' => 'Alice']);

echo "Found document: " . json_encode($document);

?>

Java

Example

import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoDatabase;

public class MongoDBConnection {

    public static void main(String[] args) {
        String uri = "mongodb://user:password@localhost:27017/mydatabase?authSource=admin";
        try (MongoClient mongoClient = MongoClients.create(uri)) {
            MongoDatabase database = mongoClient.getDatabase("mydatabase");
            System.out.println("Connected to MongoDB");
        }
    }
}

Examples

Connect to the MongoDB service using the default port.

mongodb://localhost

Connect to the MongoDB service via shell:

./mongosh Current Mongosh Log ID:66792d6b87657ebec9ed70f1Connecting to: mongodb://127.0.0.1:27017/?directConnection=true&serverSelectionTimeoutMS=2000&appName=mongosh+2.2.9Using MongoDB:7.0.11Using Mongosh:2.2.9

Now check the window where you ran the ./mongod command. You will see information about the connection source to the MongoDB server. You should see something like:

... omitted information ...2015-09-25T17:22:27.336+0800 I CONTROL  allocator: tcmalloc 2015-09-25T17:22:27.336+0800 I CONTROL  options: { storage: { dbPath: "/data/db" } }2015-09-25T17:22:27.350+0800 I NETWORK  waiting for connections on port 270172015-09-25T17:22:36.012+0800 I NETWORK  connection accepted from 127.0.0.1:37310 #1 (1 connection now open) # This line indicates a connection from localhost ... omitted information ...

MongoDB Connection Command Format

To connect to a MongoDB server using username and password, you must use the format 'username:password@hostname/dbname', where 'username' is the username and 'password' is the password.

Connecting to the default database using username and password:

$ ./mongosh MongoDB shell version: 4.0.9 connecting to: test

Connecting to the local MongoDB service using user admin with password 123456. The output is as follows:

> mongodb://admin:123456@localhost/...

Connecting to a specified database using username and password:

mongodb://admin:123456@localhost/test

More Connection Examples

Connect to a local database server using the default port.

mongodb://localhost

mongodb://fred:foobar@localhost

mongodb://fred:foobar@localhost/baz

Connect to a replica pair: server1 is example1.com, server2 is example2.com.

mongodb://example1.com:27017,example2.com:27017

Connect to a replica set with three servers (ports 27017, 27018, and 27019):

mongodb://localhost,localhost:27018,localhost:27019

Connect to a replica set with three servers, write operations applied to the primary server, and queries distributed to secondary servers.

mongodb://host1,host2,host3/?slaveOk=true

Directly connect to the first server, whether it is part of a replica set or primary/secondary server.

mongodb://host1,host2,host3/?connect=direct;slaveOk=true

If your connection has priority and requires listing all servers, you can use the above connection method.

Connect to localhost in safe mode.

mongodb://localhost/?safe=true

Connect to a replica set in safe mode and wait for at least two replica servers to successfully write, with a timeout set to 2 seconds.

mongodb://host1,host2,host3/?safe=true;w=2;wtimeoutMS=2000

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