2010

Project Voldemort

When relation database is not enough (too much?)

2010

Tomasz Nurkiewicz

• Graduated Warsaw University Of Technology (Faculty of Electronics and Information Technology)

• SCJP, SCJD, SCWCD, SCBCD• Brown belt on JavaBlackBelt.com• Few commits in:

– Commons Lang, Logback, Mule ESB• Currently working as a developer at

JAVART• http://nurkiewicz.blogspot.com

2010

What is Voldemort not?

• Relational database• Alternative API to RDB• Distributed cache

2010

...so?

• Key-value database• „Persistent HashMap”• Keywords:

– Cluster ready– Scalability (no master)– Efficient (partitioning)– High availability

• „Less than” relation database

2010

Voldemort vs. HashMap

• Partitions vs. hash-buckets• Where is my stuff? – client side

routing0 4 8 12

1 5 9 13

2 6 10 14

3 7 11 15

node1

node2

node3

node4 19

18

17

16

2010

API – StoreClient<K, V>

• getValue(K key): V• getAll(Iterable<K> keys): Map<K, V>• put(K key, V value)• delete(K key): boolean• getResponsibleNodes(K key):

List<Node>• …• extends java.util.Map<K, V>?

2010

Voldemort cluster

DEMO

node1 node2 node3 node4

localhost:6101 localhost:6102 localhost:6103 localhost:6104

2010

Connection (One to rule them all)

ClientConfig config = new ClientConfig();config.setBootstrapUrls("tcp://server:6101");SocketStoreClientFactory factory = new

SocketStoreClientFactory(config);StoreClient<K, V> client = factory.getStoreClient("users");

• No replication – efficient, but risky

2010

Store configuration (stores.xml)

• N (<replication-factor>)• R (<required-reads>)• W (<required-writes>)• Serialization

– JSON – only primitives, dates and collections

– protobuf – (Google)– String (e.g. XML)– Java (Serializable)

2010

Cluster configuration (cluster.xml)

<cluster><name>User cluster</name><server>

<id>1</id><host>192.168.0.17</host><socket-port>6101</socket-port><partitions>0, 4, 8, 12, 16</partitions>

</server>

• Persistency: MySQL, Berkeley DB, RAM

2010

Rebalancing

0 4 8 12

1 5 9 13

2 6 10 14

3 7 11 15

node1

node2

node3

node4

node5

19

18

17

16

2010

Facts of life (LinkedIn and Gilt)

GET PUT

Throughput 19K/s 16K/s

Median 0,015 ms 0,040 ms

99,99% 0,227 ms 2,551 ms

• Uptime measured in months (Gilt Groupe)• Last Thursday we lost a server and no-one

noticed (as above)

2010

Transactional/consistent?

• Logic time (vector clock)• Conflict resolution during read• Optimistic locking

– putIfNotObsolete(K key, Versioned<V> versioned)

– applyUpdate(UpdateAction<K, V> action)– ObsoleteVersionException

• R+W>N

2010

What else?

• JMX (both client and server)• Views (non-materialized)• HTTP interface (not REST though)• Hinted handoff

2010

Happy clustering!• http://project-voldemort.com

• http://www.infoq.com/presentations/Project-Voldemort-Scaling-Simple-Storage

• http://www.infoq.com/presentations/Project-Voldemort-at-Gilt-Groupe

• http://behemoth.strlen.net/~alex/voldemort-nosql_live.ppt• http://www.slideshare.net/hadoopusergroup/hadoop-and-voldemort-linkedin

• http://www.vineetgupta.com/2010/01/nosql-databases-part-1-landscape.html

• http://www.metabrew.com/article/anti-rdbms-a-list-of-distributed-key-value-stores