Slides from my 90 min talk @codecentric on MongoDB

1. MongoDB Live Coding Session
tobias.trelle@codecentric.de
@tobiastrelle
codecentric AG

2. „It‘s not my fault the chapters are short,
MongoDB is just easy to learn“
from „The Little MongoDB book“
codecentric AG

3. MongoDB User Groups by codecentric
MongoDB User-Gruppe Düsseldorf
https://www.xing.com/net/mongodb-dus
@MongoDUS
Contact: Tobias Trelle
MongoDB User-Gruppe Frankfurt/Main
https://www.xing.com/net/mongodb-ffm
Contact: Uwe Seiler
codecentric AG

4. What is MongoDB?
Named from „humongous“ = gigantic http://www.mongodb.org
NoSQL datastore, Open Source https://github.com/mongodb
support from manufacturer 10gen http://www.10gen.com
Highly scalable (scale-out)
Stores so called „documents“
Supports replication & sharding
Map/Reduce
Geospatial indexes / queries
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5. Basic structure of a MongoDB server
Server
Database
Relational counterpart But …
Flexible
Table Collection
Schema
Row Document
- Arrays
Column Field
- recursive
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6. What‘s a document?
Single record that can be stored in a collection
JSON = JavaScript Object Notation (internal representation BSON = Binary JSON)
var doc = {
title: „MongoDB_Live_Hacking.pptx“,
tags: [ „cc“, „mongodb“, „nosql“ ],
slides: [
{ nr = 1, header = „MongoDB User Groups by codecentric“},
{ nr = 2, header = „MongoDB at codedcentric WiKi“},
…
]
};
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7. Live Session
CRUD operations
Queries
Geospatial Queries
Map/Reduce
Replication
Sharding
Raw Java API & Spring Data API
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8. Geospatial Queries
Queries based on
2-dimensional coordinates
_id: "A", position: [0.001, -0.002]
_id: "B", position: [0.75, 0.75]
_id: "C", position: [0.5, 0.5]
_id: "D", position: [-0.5, -0.5]
Queries based on distances
& shapes
Details:
http://blog.codecentric.de/en/2012/02/spring-data-mongodb-geospatial-queries/
codecentric AG

9. Map/Reduce
Data processing algorithm based on two phases: map & reduce
Code execution co-located with the data
Map phase can be run in parallel (on multiple nodes etc.) on huge data sets
MongoDB map / reduce:
runs on a subset of / all documents of a collection
Map / Reduce algorithms are JS functions
Output documents of the map function are input to the reduce function
Results are documents stored in a target collection
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10. Map/Reduce example
We want to count occurences of tags assigned to our documents:
{name: „Doc 1“, tags: [ „cc“, „mongodb“, „nosql“ ] }
{name: „Doc 2“, tags: [ „cc“, „agile“ ] } Map output:
{name: „Doc 3“, tags: [ „cc“ ] } key = „cc“, value = {count: 1}
key = „mongodb“, value = {count: 1}
key = „nosql“, value = {count: 1}
Map function:
key = „cc“, value = {count: 1}
function() { this.tags.forEach( function(tag) { key = „agile“, value = {count: 1}
emit( tag, {count: 1} ) key = „cc“, value = {count: 1}
})
}
Reduce function: Reduce input:
function(key, values) { key = „cc“, values = [ {count: 1}, {count: 1}, {count: 1} ]
var result = {count: 0};
key = „mongodb“, values = [ {count: 1} ]
values.forEach(function(value) {
key = „nosql“, values = [ {count: 1} ]
result.count += value.count;
key = „agile“, values = [ {count: 1} ]
});
return result;
}
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11. MongoDB Replication
A cluster is called „replica set“
Uses Master/Slave replication
Writes from clients go to the master only
If the master goes down, the slaves elect a new master (n > 2)
Replica set w/ n = 3
Slave 1
Client Master
Slave 2
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12. MongoDB Sharding
Data is distributed over n nodes, each record is persisted only once
Data only on the shard nodes
Config Server = book keeper, knows where the data is
Switch: Gateway for clients
Sharding setup
Config
Server Shard 1
Shard 2
Client Switch
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13. MongoDB Sharding in Production
Each shard is a replica set + 3 config servers
Source: http://www.mongodb.org/display/DOCS/Sharding+Introduction
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14. MongoDB Sharding Example: Initial State
mongos> sh.status()
--- Sharding Status ---
sharding version: { "_id" : 1, "version" : 3 }
shards: 2 Shards
{ "_id" : "shard0000", "host" : "tmp-pc:9000" }
{ "_id" : "shard0001", "host" : "tmp-pc:9001" }
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
{ "_id" : "data", "partitioned" : true, "primary" : "shard0000" }
data.foo chunks:
shard0000 1
{ "age" : { $minKey : 1 } } -->> { "age" : { $maxKey : 1 } } on : shard0000 { "t" : 1000,
"i" : 0 }
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15. MongoDB Sharding Example: Multiple Chunks
mongos> sh.status()
--- Sharding Status ---
sharding version: { "_id" : 1, "version" : 3 }
shards: 2 Shards
{ "_id" : "shard0000", "host" : "tmp-pc:9000" }
{ "_id" : "shard0001", "host" : "tmp-pc:9001" }
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
{ "_id" : "data", "partitioned" : true, "primary" : "shard0000" }
data.foo chunks:
shard0001 4
shard0000 5
Chunks
{ "age" : { $minKey : 1 } } -->> { "age" : 50 } on : shard0001 { "t" : 2000, "i" : 0 }
are equally
distributed { "age" : 50 } -->> { "age" : 53 } on : shard0001 { "t" : 3000, "i" : 0 }
{ "age" : 53 } -->> { "age" : 54 } on : shard0001 { "t" : 4000, "i" : 0 }
{ "age" : 54 } -->> { "age" : 58 } on : shard0001 { "t" : 5000, "i" : 0 }
{ "age" : 58 } -->> { "age" : 60 } on : shard0000 { "t" : 5000, "i" : 1 }
{ "age" : 60 } -->> { "age" : 63 } on : shard0000 { "t" : 1000, "i" : 14 }
{ "age" : 63 } -->> { "age" : 65 } on : shard0000 { "t" : 1000, "i" : 11 }
{ "age" : 65 } -->> { "age" : 69 } on : shard0000 { "t" : 1000, "i" : 12 }
{ "age" : 69 } -->> { "age" : { $maxKey : 1 } } on : shard0000 { "t" : 1000, "i" : 4 }
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16. MongoDB API
Drivers for many languages (Java, Ruby, PHP, C++, …)
Low level Java API: MongoDB Java Driver
Spring Data MongoDB: Repository Support + Objekt/Collection Mapping
Spring Data
CrudRepository PagingAndSortingRepository
Spring Data Spring Data Spring Data Spring Data
JPA MongoDB Neo4j …
JpaRepository MongoRepository GraphRepository
MongoTemplate Neo4jTemplate
Embedded REST
JPA Mongo Java Driver
JDBC
RDBMS MongoDB Neo4j …
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17. QUESTION?
Tobias Trelle
codecentric AG
Merscheider Str. 1
42699 Solingen
tel +49 (0) 212.233628.47
fax +49 (0) 212.233628.79
mail Tobias.Trelle@codecentric.de
twitter @tobiastrelle
www.codecentric.de
www.mbg-online.de
blog.codecentric.de
www.xing.com/net/mongodb-dus
codecentric AG 20.08.2012 17