Mongodb

Gagan | Rohith | Sunil

“MongoDB (from "humongous") is a scalable, high-performance, open source, schema-free, document-oriented database.”

- mongodb.org

Created by 10gen

Features

• Document Oriented Storage• Querying• Auto Sharding• Replication Set

Document oriented storageDocument 1: FirstName=“raj", Address=“bogadi", Hobby=“stamp collection"

Document 2: FirstName=“raghu", Address=“25, kuvempu nagar", Children=(“ram,10", “hari,8", “ramya,5”)

• BSON• JSON

• JSON Notation• db.people.insert({FirstName:’raj’,Address=‘bogadi’,Hobby=‘stamp

collection’})

Querying

• Collections == Tables

• Documents/objects == Records/rows

SQL Statement  Mongo Query Language Statement 

CREATE TABLE USERS (a Number, b Number);

implicit; can be done explicitly 

INSERT INTO USERS VALUES(1,1); db.users.insert({a:1,b:1})

SELECT * FROM users; db.users.find()

SELECT * FROM users WHERE age=33; db.users.find({age:33})

SELECT * FROM users WHERE age=33 ORDER BY name;

db.users.find({age:33}).sort({name:1})

SELECT * FROM users WHERE age>33; db.users.find({'age':{$gt:33}})

SELECT * FROM users WHERE age<33; db.users.find({'age':{$lt:33}})

DEMO (Part 1)

ShardingSharding is the partitioning of data among multiple machines in an order-preserving manner.

SHARDING IN MONGODB:Auto –Sharding (only needs shard key ).Automatic load Balancing.Scaling out to thousands of nodes.Availability and automated failover

Architectural Overview

OperationsThe config server => Meta-data

The mongos process =>Routing & Coordination

Mongod=> Mongo Demon(Mysqld)

Config server

Mongos

Shards

Architectural Overview

Operation Types

Operations on a sharded system fall into one of two categories. global Targeteddb.foo.find( { x : 300, age : 40 } ) (Targeted)db.foo.find( { age : 40 } ) (Global)

Flowchart

App ServerApp Server Client(Mongos)Client

(Mongos) Configuration ServerConfiguration Server

DECISIONGlobal

Targeted

DECISIONGlobal

Targeted

Shard3Shard3

Shard4Shard4

Shard2Shard2

Shard1Shard1

Sharding and Failover

NO SINGLE POINT FAILURE

Failure of->Mongos process->Single mongod server->Failure of all mongod servers comprising a shard.->Config server.

Master and Slave

REPLICA SETS

Shards Architecture Representation

Replication Set

A Set

A Set

A Set

A Set

Election Algorithm

Periodically exchange Maxappliedoptime with all other nodes using the following format(selfid,maxoptime) .If nodes maxoptime is more send NO or else send YES(Arbitrer).The node getting the majority of yes and see majority of nodes will be elected as Primary.The process is repeated periodically.

Election Algorithm(Flow)server-a: primary oplog: (a1,a2,a3,a4,a5)server-b: secondary oplog: (a1)server-c: secondary oplog: (a1,a2,a3)…// server-a goes down…server-b: secondary oplog: (a1)server-c: secondary oplog: (a1,a2,a3)...server-b: secondary oplog: (a1)server-c: primary oplog: (a1,a2,a3) // c has highest ord and becomes primary...server-b: secondary oplog: (a1,a2,a3)server-c: primary oplog: (a1,a2,a3,c4)...server-a resumes...server-a: recovering oplog: (a1,a2,a3,a4,a5)server-b: secondary oplog: (a1,a2,a3)server-c: primary oplog: (a1,a2,a3,c4)…server-a: recovering oplog: (a1,a2,a3,c4)server-b: secondary oplog: (a1,a2,a3,c4)server-c: primary oplog: (a1,a2,a3,c4)…server-a: secondary oplog: (a1,a2,a3,c4)server-b: secondary oplog: (a1,a2,a3,c4)server-c: primary oplog: (a1,a2,a3,c4,c5,c6,c7,c8)…server-a: secondary oplog: (a1,a2,a3,c4,c5,c6,c7,c8)server-b: secondary oplog: (a1,a2,a3,c4,c5,c6,c7,c8)server-c: primary oplog: (a1,a2,a3,c4,c5,c6,c7,c8)

DEMO

BIBLOGRAPHY

Www.mongodb.org Snails in Turtleneck.com