Introduction to MongoDB

1. MongoDB
Introduction to MongoDB

2. Harun Yardımcı
Software Architect @ eBay
@nosqlcozumler

3. 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".

4. 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

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

6. NoSQL Databases

7. Document Database
• What is a document?
o PDF, Word document, text file?
Document is an associated array

8. Deployment Architecture
• Standalone
• Replica Set
• Sharded Cluster
Standalone < Replica Set < Sharded Cluster*
* Typical sharded cluster consist of replica sets in production.

9. CAP Theorem
AvailabilityConsistency
Partition
Tolerance
N/A
CA
APCP
Oracle
MySQL
Postgres
MongoDB
BigTable
HBase
Redis
Memcache
CouchDB
Cassandra
Riak
Dynamo
SimpleDB

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

11. 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

12. Replication
Redundancy, Backup, and Automatic Failover
• Master / Slave (Deprecated since 1.6)
• Replica Set

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

14. 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)

15. Replica Set
• Majority
• Voting
• Arbiters
• Hidden Members
• Delayed Members

16. 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

17. Sharding
• Why?
• Scale-out
• Store different part of data on different hosts
• Auto Balancing

18. Sharding Components
• Shards
o Standalone
o Replica Set
• Config Servers
• Mongos

19. 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" )

22. Selecting Shard Key
• Distribution of Data
• Hashed Shard Key
• Chunks and Balancing

23. Enable Sharding
You must enable sharding on each database separately
> sh.enableSharding("mydatabase")
And for each collection
> sh.shardCollection( "mydatabase.mycol", { "userId" : 1 } )

24. Thanks
If you have any questions, please feel free to ask