MongoDB Introduction to MongoDB

Harun Yardımcı Software Architect @ eBay

@nosqlcozumler

What is MongoDB? MongoDB is a scalable, high-performance, open-source, schema-free, document-oriented database developed by 10gen.

- MongoDB is named from "huMONGOus," meaning "extremely large".

Features •  Dynamic schemas •  Full, flexible index support and rich queries •  Sharding for horizontal scalability •  Replication for high availability •  Text search •  Advanced security •  Aggregation Framework and Map-Reduce •  GridFS •  Geospatial

Terminology

RDBMS MongoDB Table Collection Row Document Index Index Join Embedded Document Foreign Key Reference Partition Shard Database Database

NoSQL Databases

Document Database •  What is a document?

o  PDF, Word document, text file?

Document is an associated array

Deployment Architecture

•  Standalone •  Replica Set •  Sharded Cluster

Standalone < Replica Set < Sharded Cluster*

* Typical sharded cluster consist of replica sets in production.

CAP Theorem

Availability Consistency

Partition Tolerance

N/A

CA

AP CP

Oracle MySQL Postgres

MongoDB BigTable HBase Redis Memcache

CouchDB Cassandra Riak Dynamo SimpleDB

Standalone $ mongod

--dbpath /data/db --fork --logappend --logpath /var/log/mongod.log --journal --port 27017

Configuration File vim /etc/mongod.conf

dbpath = /data/db fork = true logappend = true logpath = /var/log/mongodb.log journal = true port = 27017

$ mongod --config /etc/mongod.conf

Replication Redundancy, Backup, and Automatic Failover

•  Master / Slave (Deprecated since 1.6)

•  Replica Set

Replica Set $ mongod

--dbpath /data/db --fork --logappend --logpath /var/log/mongod.log --journal --port 27017 --replSet set01

Replica Set Initialization Startup mongod process and connect to one of them > var cnf = { _id : 'set01', members : [

{ _id : 0, host: 'myhost1.net:27017' }, { _id : 1, host: 'myhost2.net:27017' }, { _id : 2, host: 'myhost3.net:27017' } ]

} > rs.initiate(cnf)

Replica Set •  Majority •  Voting

•  Arbiters

•  Hidden Members

•  Delayed Members

Application Concerns •  Write Concern

o  Errors Ignored o  Unacknowledge o  Acknowledged (default) o  Journaled o  Replica Acknowledged

•  Read Preferences o  primary

o  primaryPreferred

o  secondary

o  secondaryPreferred

o  nearest

Sharding •  Why?

•  Scale-out

•  Store different part of data on different hosts

•  Auto Balancing

Sharding Components •  Shards

o  Standalone o  Replica Set

•  Config Servers •  Mongos

Replica Set as a Shard Add each replica set as a shard > sh.addShard( "set01/myhost1.net:27017, myhost2.net:27017,myhost3.net:27017" ) To add standalone server as a shard.. DON’T DO IT!! > sh.addShard( "myhost9.net:27017" )

Selecting Shard Key •  Distribution of Data

•  Hashed Shard Key

•  Chunks and Balancing

Enable Sharding You must enable sharding on each database separately

> sh.enableSharding("mydatabase")

And for each collection > sh.shardCollection( "mydatabase.mycol", { "userId" : 1 } )

Thanks

If you have any questions, please feel free to ask