These slides were made for a 3 hour workshop integrate in the first edition of Startup Scholarship

1. Startup tech arsenal!
João Vazão Vasques

2. ABOUT ME
@JoaoVasques
@JoaoVasques
joao.l.v.vasques
jv@uniplaces.com

3. AGENDA

4. PART I - MongoDB

5. MongoDB topics
● Basic concepts
● Operations
● Data modeling
● Performance and tools

6. Basic concepts 1-2
● NoSQL
● No transactions
○ Eventual consistency
● No schema
○ Flexibility: code defines your schema
● Scaling (Horizontal scaling)
● Document oriented
○ BJSON

7. Basic concepts 2-2
Database
Table
Indexes
Columns
Row
Database
Collections
Indexes
Fields
Documents
Relational MongoDB

8. So we have...
Databases containing collections. A
collection is made up of documents.
Each document is made up of fields

9. Operations
● Document example (Uniplaces listing)
{
"title": "Uniplaces Mega mansion",
"rentable": false,
"location" : {
"city" : "Lisboa",
"coordinates" : {
"longitude" : -9.145782599999961,
"latitude" : 38.7234037
}
},
"apartment_details" : {
"bathrooms" : 2,
"bedrooms" : 6,
},
}

10. Operations
Insert listings - insert
db.listings.insert( { title: "Erasmus Residence", rentable: true } )
db.listings.insert( {title: "xpto", rentable: true, location: [{city:
"lisbon", coordinates: {latitude: 0, longitude: 90} } ] } )

11. Operations
Update listings - update
Syntax: update( < query>, <update>, <options>)
Problem!
We want to make "Mansion" rentable.
Solution (easy)!
db.listings.update( { title: "Uniplaces Mega Mansion"}, {rentable: true } )
Search for Mega Mansion and...

13. Operations
Update listings 2 -2
Reason: second parameter replaces the original. We replaced the entire
document with a new one. Ups!
Solution - $set
Used when you want to change a value of one, or a few, fields
db.listings.update( { title: "Uniplaces Mega Mansion"}, { $set: {rentable: true } } )
Other update modifiers: $inc, $unset, $push, $pop

14. Search listings - find (1 - 2)
Syntax: find( < query>, <projection>)
Projection
db.listings.find( { title: "Uniplaces Mega mansion"}, {rentable: 1} )
Logical operators ($and)
db.listings.find({ $and: [{ title: "Uniplaces Mega Mansion"}, {rentable: "false"}] })
Comparison operators ($gte)
db.listings.find( { "apartment_details.bedrooms" : {$gte: 2 } }, { title: 1} )
Operations

15. Search listings - find (2 - 2)
Ordering (sort: -1 descending, 1 ascending)
db.listings.find({ $gte: { "apartment_details.bedrooms" : 2 }).sort
("apartment_details.bedrooms": -1)
Paging (limit and skip)
db.listings.find().limit(3).skip(1)
Operations

16. ● MongoDB does not support Joins
● Embedded Documents
{
"title": "Uniplaces Mega mansion",
"bedrooms" : [
{
"price" : 500,
"area": 25
},
{
"price" : 700,
"area": 30
},
]
}
db.listings.find( {bedrooms: { $elemMatch: {price: { $gt: 20 }, area: 25} } })
Data modeling

17. Considerations:
● Geography
● System errors
○ ensure your backups can "survive"
● Production constraints
○ Schedule according to system usage
● Database configuration
○ Replication & Sharding
Backups 1 -3

18. Approaches to backup MongoDB systems
● Binary database dumps
○ Small
○ Don't include index content and padding
○ Cannot reflect single moment in time
● Filesystem snapshots
○ Large backup sizes
○ Accurate
○ Require filesystem and OS tools
○ Can reflect a single moment in time
■ Note: in sharding all writes must be suspended
Backups 2-3

19. Backup and restore example
● Backup database
> mongodump -v -d test -o dump
● Restore database
> mongorestore -v --db test dump
Backups 3-3

20. ● Writes to primary (only)
○ A write is fully committed once it has replicated to a majority of servers
in the set
● Reads to primary and secondary
● Consensus election in case of primary fail
Replica Sets
Secondary
Secondary
Primary
W
W
W
Secondary
W

21. END OF PART I

22. Part II - Coding Time!

23. Part II - Coding Time!
Weapons we'll be using

24. ● Web framework written in Scala & Java
● MVC paradigm
● Built on Akka
● Built in testing tools
● IDE support (Eclipse and IntelliJ IDEA)
About Play!

25. MVC
Model - View - Controller

26. Anatomy of a Play! application

27. Coding samples
routing

28. Coding samples
template engine

29. Download the demo project on Github
● https://github.com/JoaoVasques/mongodb-workshop
Challenges:
● Fire Employee
● Search employee
● Create a backup of the database and restore it
Hands on time!!!

30. ● engineering.linkedin.com
● blog.twitter.com/engineering
● facebook.com/Engineering
● engineering.foursquare.com
● nerds.airbnb.com
Cool tech blogs

31. Thank you!