MongoDB

Scalable document-oriented storage. JSON-style documents with dynamic schemas offer simplicity and power.

MongoDB supports various connectors of different quality for C, C#, C++, Erlang, Haskell, JavaScript, Java, Perl, PHP, Python, Ruby, and Scala. The company behind it, which was called 10gen until half a year ago, offers a commercial version with support. In the approximately five years since its inception, the C++-based database has likely become the most widespread NoSQL database, used by organizations such as MTV, CERN, and The New York Times.

• http://www.mongodb.org/

• http://www.mongodb.org/display/DOCS/Tutorial

• http://www.mongodb.org/display/DOCS/Commands

• http://www.mongodb.org/display/DOCS/Trees+in+MongoDB (Trees)

Notes

Geo from Python

Very simple to execut near query with mongo for simple apps

Create an index

db.posts.createIndex({ location: "2dsphere" })

Then, ensure your data is stored in GeoJSON format, like this:

db.posts.insertOne({
    title: "A post near NYC",
    location: { type: "Point", coordinates: [-73.9000, 40.7000] }
})

Once the index is created, your original geoNear query should work:

db.runCommand({
    geoNear: "posts",                   // Specifies the collection to search in
    near: [-73.9000, 40.7000],           // The point (longitude, latitude) to search near
    spherical: true,                     // Indicates the coordinates are in a spherical system (WGS84)
    maxDistance: 10000,           // Maximum distance in meters
    distanceMultiplier: 6378137          // Converts results to meters (Earth’s radius in meters)
});

Equivalent Python Code (pymongo)

from pymongo import MongoClient
from bson.son import SON

# Connect to MongoDB
client = MongoClient("mongodb://localhost:27017/")
db = client["your_database"]

# Ensure a geospatial index (for GeoJSON, use '2dsphere')
db.places.create_index([("loc", "2dsphere")])

# Run the geoNear command
query = SON([
    ("geoNear", "places"),
    ("near", {"type": "Point", "coordinates": [37.617000, 55.755000]}),  # GeoJSON format
    ("spherical", True),
    ("maxDistance", 0.1)  # Distance in meters
])

result = db.command(query)

# Print results
for place in result["results"]:
    print(place)

Admin

mongocli drop db

use db
db.dropDatabase()

Mongo restore

mongorestore --drop --host 192.168.100.33 --port 27017 -u "user" -p "password" --authenticationDatabase "authdb" -d HOST FOLDER

Users

use mydbname;
db.getUsers()

db.createUser(
    {
        user: "imauser",
        pwd: "mypass",
        roles: []
    }
)

Grant role

db.grantRolesToUser("imauser", ["myrole"])

Backup mongo example

$ mongodump --port 27017 -u "myuser" -p "mypass" --authenticationDatabase "authdb" --db mydb --out /tmp/mo

Connect to Mongo with mongo-shell

$ mongo --port 27017 -u "myuser" -p "mypass" --authenticationDatabase "mydbname" somename
> show dbs

Mongo Docker Setup

Setup a replica set with Docker containers

# docker run -p 30001:30001 --name mongo1 --net my-mongo-cluster mongo mongod --replSet my-mongo-set --port 30001
# docker run -p 30002:30002 --name mongo2 --net my-mongo-cluster mongo mongod --replSet my-mongo-set --port 30002
# docker run -p 30003:30003 --name mongo3 --net my-mongo-cluster mongo mongod --replSet my-mongo-set --port 30003

Start containers

docker start mongo1[2,3]

Important:

• The port inside the container must be the same as the one mapped externally; otherwise, the driver may have issues connecting to the replica set.

• The client machine should be able to resolve mongo1, mongo2, etc., via DNS.

Cluster setup complete

Connect to a node for configuration

# docker exec -it mongo1 mongo --port 30001

Mongo shell

db = (new Mongo('localhost:30001')).getDB('test')
test
config = {"_id" : "my-mongo-set","members" : [{"_id" : 0,"host" : "mongo1:30001"},{"_id" : 1,"host" : "mongo2:30002"},{"_id" : 2,"host" : "mongo3:30003"}]}
rs.initiate(config)

Document is saved in the Mongo folder

Connect to Replica Set

mongo 'mongodb://$(basename $BASH_SOURCE):$(basename $BASH_SOURCE)@somename_mongo1_1:27001,somename_mongo2_1:27002,somename_mongo3_1:27003/somename?replicaSet=somename'  --authenticationDatabase 'somename'

Note: Different formats exist in different MongoDB versions. The following is for MongoDB 3.4.

my-mongo-set:SECONDARY> rs.slaveOk()  # Allows reading from the secondary replica
my-mongo-set:SECONDARY> show dbs

See also the Python implementation in the moqscripts project: [MongoTest](http://vertx.io/docs/vertx-mongo-client/java/).

Activate authentication in Mongo Replica Setup

For a replica set, it is important to provide a key for authentication between instances.

mongod --keyFile <path-to-keyfile> --replSet <replicaSetName> --bind_ip localhost,<ip address of the mongod host>

Copy the key file or certificate to the machine and start MongoDB as shown above.

References: - [Update an Existing MongoDB Replica Set to Use Key Authentication](http://pe-kay.blogspot.de/2016/02/update-existing-mongodb-replica-set-to.html) - [MongoDB Internal Authentication Documentation](https://docs.mongodb.com/manual/core/security-internal-authentication/)

Example setup:

mkdir -p /etc/moq/mongo/
echo "qwerty" > /etc/moq/mongo/key
chmod 600 /etc/moq/mongo/key
chown 999:999  /etc/moq/mongo/key

Use the key file in the MongoDB startup command:

--keyFile /etc/moq/mongo/key

Docker restore database

Copy an example to the container

docker cp /somepath mongo1:/tmp/

Restore database

docker exec -it mongo1 mongorestore --port 30001 --drop -d /somepath /tmp/somepath/