This document discusses MongoDB replication and sharding. It begins with an introduction to MongoDB and its data model. It then covers replication with master-slave and replica sets. It also discusses sharding components including shard servers, config servers, and mongos routers. It provides examples of setting up replica sets, adding shards, and combining replica sets with sharding. The document encourages trying these techniques yourself and sharing experiences.

1. MongoDB
Replication and Sharding
Workshop
by Harun Yardımcı
@h_yardimci

2. What we will do today?
- Following Replicated Shard

3. What is MongoDB?
● Document-oriented database
● in MongoDB you store JSON-like documents
with dynamic schemas
● Bridge the gap between key-value stores
and relational databases

4. What is MongoDB?

5. Why MongoDB?
● Document-oriented
● High performance
● High availability
● Easy scalability
● Rich query language + MapReduce

6. Use Cases
Well Suited
● Archiving and event logging
● Document and Content Management Systems
● ECommerce Often in combination with an RDBMS for the final
order processing and accounting
● Gaming Small read/writes are a good fit for MongoDB
● Mobile Specifically, the server-side infrastructure of mobile
systems. Geospatial.
● Operational data store of a web site MongoDB is very good at
real-time inserts, updates, and queries. Specific web use
case examples:
● content management
● comment storage, management, voting
● user registration, profile, session data
● Real-time stats/analytics

7. What is a Document?
{'id':1, 'category_name' : 'Computer'}

8. Mongo Data Model
Key:
'category_name'
Value:
'Computer'
Field: key-value pair
'category_name':'Computer'
Document: set of fields
{'id':1, 'category_name' : 'Computer'}

9. Mongo Data Model
Collection: set of documents
(say categories)
{'id':1, 'category_name' : 'Computer'},
{'id':2, 'category_name' : 'Mobile'},
...
Database: set of collections
categories
products
members

10. Simple Usage and Introduction

11. First Run
$ mkdir -p /data/db/ Create a data path
and give permissions
$ chown -R mongod:mongod /data/db/
Start mongod deamon
$ mongod [--dbpath /data/db/] &
$ mongo Connect to mongod
> show dbs
> use admin
> show collections

12. Intro
CRUD Operations
> use testdb
switched to db testdb
> j = { name : "deneme" };
{"name" : "deneme"}
> t = { x : 3 };
{ "x" : 3 }
> db.col.save(j);
> db.col.insert(j); /* see the error message */
> db.col.save(t);
> for (var x = 1; x <= 20; x++) db.col.save({x:x, j:x*x})
>

13. Intro
> db.col.find();
{ "_id" : ObjectId("4c2209f9f3924d31102bd84a"), "name" : "mongo" }
{ "_id" : ObjectId("4c2209fef3924d31102bd84b"), "x" : 3 }
{ "_id" : ObjectId("4f971ab51c3fde3bc55f286f"), "x" : 1, "j" : 1 }
{ "_id" : ObjectId("4f971ab51c3fde3bc55f2870"), "x" : 2, "j" : 4 }
{ "_id" : ObjectId("4f971ab51c3fde3bc55f2871"), "x" : 3, "j" : 9 }
…
has more
> db.col.remove({"x":"3"});
>

14. The Big Picture!

15. Replication
Two Types of Replications
● Master / Slave Replication
● ReplicaSet

16. Master-Slave Rep.
$ mkdir -p /data/db/ms Different data paths
$ mkdir -p /data/db/sl for each instances
$ bin/mongod --master [--port <port>] [--dbpath /data/masterdb/]
$ bin/mongod --slave [--port <port>] --source <masterhostname>[:<port>]
[--dbpath /data/slavedb/]
…
> db.printReplicationInfo() - on master
> db.printSlaveReplicationInfo() - on slave
> use admin
> db.runCommand({resync: 1})

17. ReplicaSet - Voting
Consensus Vote
For a node to be elected primary, it must receive a
majority of votes by the following formula
(floor(5/2)+1)
Arbiters - {_id: 2, host: 'localhost:27019', arbiterOnly:
true}
Reachable Node – heartbeat
Each replica set is limited to 12 total nodes and 7 voting nodes.

18. ReplicaSet
Starting The Nodes myRSet
localhost localhost localhost
27017 27018 27019
$ mkdir -p /data/r0 /data/r0 /data/r1 /data/r2
$ mkdir -p /data/r1
$ mkdir -p /data/r2
$ mongod --replSet myRSet --port 27017 --dbpath /data/r0
$ mongod --replSet myRSet --port 27018 --dbpath /data/r1
$ mongod --replSet myRSet --port 27019 --dbpath /data/r2

19. ReplicaSet
Initiating The Set
> config = {_id: 'myRSet', members: [
{_id: 0, host: 'localhost:27017'},
{_id: 1, host: 'localhost:27018'},
{_id: 2, host: 'localhost:27019'}]
}
> rs.initiate(config);
{
"info" : "Config now saved locally. Should come online in about a
minute.",
"ok" : 1
}
> rs.status();

20. Sharding
Sharding Components
● Shard Servers
● Config Servers
● mongos Router

21. Sharding

22. Sharding
$ mkdir -p /data/db/s1 /data/db/s2 /data/db/config
$ mongod --shardsvr --port 27001 --dbpath /data/db/s1 &
$ mongod --shardsvr --port 27002 --dbpath /data/db/s2 &
$ mongod --configsvr --port 27003 --dbpath /data/db/config &
$ mongos --port 27017 --configdb localhost:27003 &

23. Sharding
Add Shards to Config
Connect to mongos to add shards
> use admin
> db.runCommand( {addShard : "localhost:27001"} );
{"ok" : 1 , "added" : "localhost:27001"}
> db.runCommand( {addShard : "localhost:27002"} );
{"ok" : 1 , "added" : "localhost:27002"}

24. Sharding
Enable Sharding
> db.runCommand( { enablesharding: "test_database"} );
{ "ok" : 1 }
> db.runCommand( { shardcollection :
"test_database.myCollection", key : {"_id" :1} })
{ "collectionsharded" : "test_database.myCollection",
"ok" : 1 }

25. ReplicaSet + Sharding
host1$ mongod --shardsvr --replSet rs_a
host2$ mongod --shardsvr --replSet rs_a Same replica set name
host3$ mongod --shardsvr --replSet rs_a
> cfg = {
_id : "rs_a",
members : [
{_id : 0, host : "host1:27018", priority : 1},
{_id : 1, host : "host2:27018", priority : 1},
{_id : 2, host : "host3:27018", priority : 0}
]
}
> rs.initiate(cfg)

26. ReplicaSet + Sharding
host1$ mongod --configsvr
host2$ mongod --configsvr
host3$ mongod --configsvr
$ mongos --configdb host1:27019,host2:27019,host3:27019
$ mongo
> db.adminCommand( { addShard :
"rs_a/host1:27018,host2:27018,host3:27018" } )
> db.adminCommand( { addShard :
"rs_b/host4:27018,host5:27018,host6:27018" } )
> db.adminCommand( { addShard :
"rs_c/host7:27018,host8:27018,host9:27018" } )

27. What is Next?
Please
Try it Yourself
and
Share Your Experiences
Thanks