introducing hibernate ogm: porting jpa applications to nosql, sanne grinovero (jboss by redhat)

OpenBlend LjubljanaSeptember 15th, 2011

Sanne GrinoveroSoftware Engineer at Red Hat

About me• Hibernate

• Hibernate Search

• Hibernate OGM

• Infinispan

• Lucene Directory

• Infinispan Query

in.relation.to/Bloggers/Sanne

Twitter: @SanneGrinovero

What is Hibernate OGM ?

JPA for NoSQL

• initially Key/Value store• in particular Infinispan

Relational Databases• Transactions • Referential integrity• Simple Types• Well understood- tuning, backup, resilience

Relational Databases

But scaling is hard!-Replication-Multiple instances w/ shared disk-Sharding

Relational Databases on a cloud

Master/replicas: which master?

A single master? I was promised elasticity

Less reliable “disks”

IP in configuration files? DNS update times?

Who coordinates this? How does that failover?

¬SQLbeing a not-only-thatone

basically makes it a definition of “everything else too”

“no-category”

No-SQL goalsVery different• Large datasets• High availability• Low latency / higher throughput• Specific data access pattern• Specific data structures• ...

• Document based stores • Column based • Graph oriented databases• Key / value stores• Full-Text Search

NotOnlySQL

Flexibility at a cost

•Programming model•one per product :-(

•no schema => app driven schema•query (Map Reduce, specific DSL, ...)•data structure transpires•Transaction•durability / consistency

Quick Infinispan introduction

Distributed Key/Value store•(or Replicated, local only efficient cache, invalidating cache)

Each node is equal•Just start more nodes, or kill some

No bottlenecks•by design

Cloud-network friendly•JGroups•And “cloud storage” friendly too!

Infinispan ABC

map.put( “user-34”, userInstance );

map.get( “user-34” );

map.remove( “user-34” );

It's a ConcurrentMap !

map.put( “user-34”, userInstance );

map.get( “user-34” );

map.remove( “user-34” );

map.putIfAbsent( “user-38”, another );

Something more about Infinispan

● Support for Transactions (XA)● CacheLoaders

●Cassandra, JDBC, Amazon S3 (jclouds),...● Tree API for JBossCache compatibility● Lucene integration

● Two-fold● Some Hibernate integrations

● Second level cache● Hibernate Search indexing backend

Cloud-hack experiments

Let's abuse of Hibernate's second level cache design, using Infinispan's implementation:- usually configured in clustering mode INVALIDATION. Let's use DIST instead.- Disable expiry/timeouts.

What's the effect on your cloud-deployed database?

Cloud-hack experiments

Now introduce Hibernate Search: - full-text queries should be handled by Lucene, NOT by the database.

Hibernate Search identifies hits from the Lucene index, but loads them by PK. *by default

Cloud-hack experiments

Load by PK ->second level cache ->

Key/Value store

FullText query ->Hibernate Search ->

Lucene Indexes

Cloud-hack experiments

Load by PK ->second level cache ->

Key/Value store

FullText query ->Hibernate Search ->

Lucene Indexes

So what if you shut down the database?

Cloud-hack experimentsLoad by PK ->

second level cache ->Key/Value store

FullText query ->Hibernate Search ->

Lucene Indexes

So what if you shut down the database?•No relational/SQL queries•You won't be able to write!

Goals

•Encourage new data usage patterns•Familiar environment•Ease of use•easy to jump in•easy to jump out•Push NoSQL exploration in enterprises•“PaaS for existing API” initiative

What it does

•JPA front end to key/value stores•Object CRUD (incl polymorphism and associations)•OO queries (JP-QL)

•Reuses•Hibernate Core•Hibernate Search (and Lucene)•Infinispan

•Is not a silver bullet•not for all NoSQL use cases

Concepts

Schema or no schema?

•Schema-less•move to new schema very easy•app deal with old and new structure or migrate all

data•need strict development guidelines

•Schema•reduce likelihood of rogue developer corruption•share with other apps•“didn’t think about that” bugs reduced

Entities as serialized blobs?

•Serialize objects into the (key) value•store the whole graph?

•maintain consistency with duplicated objects•guaranteed identity a == b•concurrency / latency•structure change and (de)serialization, class definition

changes

OGM’s approach to schema

•Keep what’s best from relational model•as much as possible•tables / columns / pks

•Decorrelate object structure from data structure•Data stored as (self-described) tuples•Core types limited

•portability

OGM’s approach to schema

•Store metadata for queries•Lucene index

•CRUD operations are key lookups

• Entities are stored as tuples (Map<String,Object>) • The key is composed of

• table name• entity id

• Collections are represented as a list of tuple- The key is composed of:

• table name hosting the collection information• column names representing the FK• column values representing the FK

How does it work?

Queries

•Hibernate Search indexes entities•Store Lucene indexes in Infinispan•JP-QL to Lucene query transformation

•Works for simple queries•Lucene is not a relational SQL engine

select a from Animal a where a.size > 20

> animalQueryBuilder.range().onField(“size”).above(20).excludeLimit().createQuery();

select u from Order o join o.user u where o.price > 100 and u.city = “Paris”> orderQB.bool() .must( orderQB.range() .onField(“price”).above(100).excludeLimit().createQuery() ) .must( orderQB.keyword(“user.city”).matching(“Paris”) .createQuery()).createQuery();

Demo

Why Infinispan?

•We know it well•Supports transactions (!)

•Research is going on to provide “cloud transactions” on more platforms

•It supports Lucene indexes distribution•Easy to manage in clouds•It's a key/value store with support for Map/Reduce

•Simple•Likely a common point for many other “databases”

Why Infinispan?

•Map/Reduce as an alternative to indexed queries•Might be chosen by a clever JP-QL engine

•Supports – experimentally – distributed Lucene queries•Since ISPN-200, merged last week

Why all this ?

Developers will only need to think about

• JPA models

• JP-QL queries

Everything else is perfomance tuning, including:

•Move to/from different NoSQL implementations

•Move to/from a SQL implementation

•Move to/from clouds/laptops

•JPA is a well known standard: move to/from Hibernate :-)

Summary•JPA for NoSQL•Reusing mature projects•Keep the good of the relational model•Query via Hibernate Search

•JP-QL support on its way•Still early in the project•Only Infinispan is integrated: contributions welcome!

Summary

•Performance / scalability is different•Isolation is different

http://www.hibernate.org/subprojects/ogm.html

http://www.jboss.org/jbw2011keynote.htmlhttps://github.com/Sanne/tweets-ogm

Q + A