6 Février 2018
Introduction à la base de données NoSQL
Apache Cassandra
Nicolas MENOUX
Chief Data Technology Officer

From RDBMS to NoSQL
1970-… 2000-…

NoSQL genesis
#nosql mouvement in 2009
Johan Oskarsson

NoSQL a new paradigm
• Large Volume of Data
• Fast concurrent users queries
• Dynamic schemas (schema less)
• Auto-sharding
• Replication
• Horizontally Scalable
• Eventually consistent

Eventually Consistent

CAP Theorem (only 2 of 3)

No more relations !

NoSQL databases

A good blend !
• Peer-to-Peer
• Key-Value pairs
• Tunable consistency
• Wide rows
• Fast write throughput
July 2008
Google code
2007
2006

Cassandra characteristics
February 2010

75 000 nodes
10 PB
Cassandra in Production
2 500 nodes
420 PB
1 000 000 000 000 reqs / day
11 500 000 reqs / sec100 nodes
250 PB

Multi-Datacenter Cassandra on Raspberry Pi's
http://blablatech.com/blog/cassandra-gets-in-blablacar

Fault tolerance : Data Replication

Built-in WAN sync

How Cassandra stores data (nodes & vnodes)
Hash(partition key) =

Data Model
SELECT id, age FROM users WHERE id=xxx
Data Models
SELECT age, count(*) FROM users GROUP By age
SELECT id, nom FROM users JOIN names ON users.id = names.id
…
NOSQL = From Query to Data Model

Data Model : Column oriented

Cassandra : Data types

Primary Key

Cassandra : Primary keys
Compound primary key
Composite partition key

Cassandra Query Language : CQL
TTL :
Timestamp :

Performance : Linear scalability

Write path
flush

Last Write Win (LWW)

Last Write Win (LWW)

Compactions

Compaction Strategies
SizeTieredCompactionStrategy (STCS)
LeveledCompactionStrategy (LCS)
TimeWindowCompactionStrategy (TWCS)
DateTieredCompactionStrategy (DTCS)

Tunable consistency

Write consistency (RF=3, ONE)

Write consistency (RF=3, QUORUM)
Multi-DC
Delay
Alternative
LOCAL_QUORUM

Read consistency : (RF=3, QUORUM)
Background node repair : read_repair_chance (10%)

Read consistency : (RF=3, LOCAL_QUORUM)

Conclusion
Cassandra is … Not a general purpose solution
But very good in
Scalability
Write(/Read) performance
NoSPoF
DataModel
Multi-DC native
Spark Integration
TimeSeries Data
https://academy.datastax.com

Q&A
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install default-jdk
echo "deb http://www.apache.org/dist/cassandra/debian 311x main" | sudo tee -a /etc/apt/sources.list.d/cassandra.sources.list
sudo apt-key adv --keyserver pool.sks-keyservers.net --recv-key A278B781FE4B2BDA
sudo apt-get update
sudo apt-get install cassandra
sudo systemctl start cassandra.service
Ubuntu
docker run --name cassandra-server -d cassandra
sleep 20
docker run -it --link cassandra-server:cassandra --rm cassandra cqlsh cassandra
Docker