Scaling Hibernate with Terracotta

Scaling Hibernate with Terracotta Alex Miller (@puredanger)

Architecture and Scale

Applications in Three Tiers Client Server Database

How do we scale? Client Client Client Server Server Server Database

But what about failover?

Option 1: Servers share state Client Client Client Server Server Server Database

How? • RMI • JMS • Custom (JGroups, etc)

Option 2: Database (“stateless”) Client Client Client Server Server Server Database

Stateless == “State in the database” • Database load • Serialization to and from the database • Network bandwidth • Object / relational mapping due to impedance mismatch

Option 3: Terracotta! Client Client Client Server Server Server Terracotta Terracotta Terracotta Terracotta Terracotta Database Server Server Instance Instance

Why is this better? • Hub and spoke vs peer to peer • Avoid object / relational translation • Avoid serialization • Reduce database overload • Programming model you already know • Focus on your app, not scalability and high availability

What state should go in Terracotta? Appropriateness Memory Terracotta Database Data Lifetime

How does Terracotta work?

Core Concepts • Roots • Instrumented Classes • Locks • Integration Modules

Clustered Heap App App app = new App(); app.run();

Clustered Heap App EmployeeManager employeeMgr = new EmployeeManager(); Employee Manager Object lock Object lock = new Object(); Map<String,Employee> = new HashMap<String,Employee>(); HashMap employees

Clustered Heap App Employee " U9 9 4 1 1 " M anag er Ob ject lock Employee.AC T IV E = = 1 Employee " Gandalf" HashM ap employees Employee employee = new Employee( “U99411”, “Gandalf”, Employee.ACTIVE);

Clustered Heap App employeeMgr.addEmployee(employee); Employee "U99411" Manager Object lock Employee.ACT IVE == 1 "U99411" Employee "Gandalf" HashMap employees synchronized(lock) { employees.put(e.getId(), e); }

Clustered Heap App Employee "U99411" Manager Object lock Employee.ACT IVE == 1 "U99411" Employee "Gandalf" HashMap employees "U23526" Employee "U23526" Employee.ACT IVE = 1 "U99411"

Conﬁguration • Roots • app.App.employeeMgr - a root of the clustered heap • Instrumented classes • app.* - instrument app classes at load time • Locks • employeeMgr.addEmployee() -> cluster synchronized blocks

Integration Modules • Pre-built conﬁguration • Integration with speciﬁc 3rd-party libraries • Hibernate • Spring • Ehcache • Quartz • Lucene • many more...

Scaling Hibernate • Hibernate Second Level Cache • Clustered detached entities • Close session, detach entities • Cluster those entities in Terracotta • Merge with new session later

Hibernate Caching Application Thread Application Thread Session Session 1st Level Cache Cache Cache Cache Concurrency Concurrency Concurrency Hibernate Strategy Strategy Strategy CacheProvider 2nd Level Cache Cache Cache Cache Region Region Region Database

Entity and collection caches • Entity and collection cache regions • Mark a Hibernate entity or a collection in an entity as @Cacheable • Specify a cache concurrency strategy • ReadOnly, ReadWrite, NonstrictReadWrite, Transactional • Turn on second level caching in the Hibernate conﬁg

Query Cache • Query cache regions • Mark HQL, Criteria, Query as cacheable • Store result set id values • Timestamp cache region - last update time for each entity type • Useful for caching natural key lookups (non-primary key) • ...but lots of hidden issues

Terracotta Hibernate Second Level Cache • Easy integration and conﬁguration • Supports entity, collection, and query cache regions • Supports read-only, read-write, and nonstrict-read-write cache concurrency strategies • Hibernate-speciﬁc tooling • High performance with cache coherency

Enabling Second Level Cache • Mark your entities with a cache concurrency strategy • In hibernate.cfg.xml: <cache usage="read-write"/> • With annotations: @Cache(usage=CacheConcurrencyStrategy.READ_WRITE) • hibernate.cfg.xml • <property name="cache.use_second_level_cache">true</property> • <property name="cache.provider_class"> org.terracotta.hibernate.TerracottaHibernateCacheProvider</property>

Enabling Second Level Cache • Deﬁne the tc-hibernate-cache.xml in your classpath <?xml version=”1.0” encoding=”UTF-8”?> <terracotta-hibernate-cache-configuration> <default-configuration> <time-to-idle-seconds>7200</time-to-idle-seconds> <time-to-live-seconds>7200</time-to-live-seconds> </default-configuration> <cache> <region-name>org.terracotta.authinator.domain.Account</region-name>  <configuration> <time-to-idle-seconds>600</time-to-idle-seconds> <time-to-live-seconds>600</time-to-live-seconds> </configuration> </cache> </terracotta-hibernate-cache-configuration> • Add the Terracotta Hibernate cache provider jar to your classpath • -cp terracotta-hibernate-cache-1.0.0.jar • Add the Terracotta Hibernate cache agent jar to your command line • -javaagent:terracotta-hibernate-agent-1.0.0.jar

Tooling Demo

Performance - Read-Only Comparison Throughput Latency 200K 100 Transactions per second 80 150K Avg Latency (ms) 60 100K 40 50K 20 0K 0 Database IMDG EhcacheTerracotta Database IMDG EhcacheTerracotta

How else is Terracotta used? • Distributed cache • Clustered HTTP sessions • Batch processing • Grid • Messaging and events

Who Uses It? • e-Commerce • Online gaming • Financial services • Travel & leisure • Social networking

Thanks! • Terracotta Open Source JVM clustering: • http://www.terracotta.org • Apress: “The Deﬁnitive Guide to Terracotta” • by Ari Zilka, Alex Miller, Geert Bevin, Jonas Boner, Orion Letizi, Taylor Gautier • Alex Miller • @puredanger • http://tech.puredanger.com

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Scaling Hibernate with Terracotta

by Alex Miller on Aug 04, 2009

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