OpenJPA Slice extends JPA for horizontally partitioned database environment. This session was originally presented in JavaOne 2010.

1. Scale Java Persistence API Applications with OpenJPA Slice Pinaki Poddar [email_address]

8. Architectural tiers of a typical JPA-based application User Application OpenJPA Standard JPA API JDBC API 400 million records

9. Architectural tiers of a Slice-based application User Application OpenJPA Standard JPA API JDBC API Slice OpenJPA is a plugabble platform User-defined Data Distribution Policy 4x100 million records

10. Separate Persistence Unit configured to partitioned databases C A [1] D A Unit A C A [2] C B [1] D B Unit B C B [2] C C [1] D C Unit C C C [2]

11. Same persistence unit switches contexts to partitioned databases C A [1] D A Persistence Unit C A [2] C C [2] C C [1] C B [2] C B [1] D B D C

12. Same persistence unit connected to partitioned databases C[1] D A Persistence Unit C[2] D B D C

13. Features of Slice Slice-based User Application OpenJPA Standard JPA API JDBC API Slice No changes to Application code User-defined Data Distribution Policy Flexible per-Slice Configuration Parallel Query Execution Heterogeneous Databases Master-based Sequence Targeted Query No changes to Domain Model User-defined Query Target Policy No changes to Database Schema 4x100 millon records

19. Distribution Policy decides target slice for each instance public interface DistributionPolicy { /** * Decide the name of the slice where the given persistent * instance would be stored. * * @param pc The newly persistent or to-be-merged object. * @param slices name of the configured slices. * @param context persistence context managing the given instance. * * @return identifier of the slice. This name must match one of the * configured slice names. * @see DistributedConfiguration#getSliceNames() */ String distribute ( Object pc, List<String> slices, Object context); } Slice runtime will call this method while persisting or merging a root instance. The instance and its persistent closure will be stored in the returned slice.

20. Details on Distribution Policy a b em.persist(a); // or em.merge(a); persistence context MyPolicy.distribute(a,…) { return “One” ; } One One < property name=&quot; openjpa.slice.DistributionPolicy &quot; value=“ acme.org.MyPolicy &quot;/> Slice attaches moniker to managed instance as it enters a persistence context Slice runtime calls User Application CascadeType.PERSIST CascadeType.MERGE c One

22. An example domain model

23. Instances that violate persistent closure must be replicated Stock CSCO Ask-152 Bid-153 Trader-1 Trader-2 Trade-15 Stock GS Ask-210 Bid-211 Trader-7 Trader-1 Trade-21 slice.One slice.Two Trader-1 will violate collocation constraint and must be replicated across all slices. Data partitioned by Stock sectors

25. Replication Policy public interface ReplicationPolicy { /** * Decide the name of the slices where the given persistent * instance would be replicated. * * @param pc The newly persistent or to-be-merged object. * @param slices name of the configured slices. * @param context persistence context managing the given instance. * * @return identifier(s) of the slice. Each name must match one of the * configured slice names. * @see DistributedConfiguration#getSliceNames() */ String[] replicate ( Object pc, List<String> slices, Object context); } Slice runtime will call this method while persisting any replicated instance.

27. Query Target Policy decides target slice for each query public interface QueryTargetPolicy { /** * Decide the name of the slice(s) where the given query * will be executed. * * @param query The query string to be executed. * @param params the bound parameters of the query. * @param language the language of the query * @param slices name of the configured slices * @param context persistence context executing the query. * * @return identifier of the target slices. Null value implies * all configured slices. */ String[] getTargets ( String query, Map params, String language, List<String> slices, Object context); } Slice runtime will call this method for every query. Default policy targets all available slices.

28. Intrusive way to control target slices for a query EntityManager em = …; String jpql = &quot; SELECT p FROM Person p where p.name=:name ”; TypedQuery <Person> query1 = em.createQuery(jpql, Person. class ); // Set a single slice as query target query1.setHint( SlicePersistence.HINT_TARGET , “ One &quot;); List < Person > result1 = query1.setParameter(“ name ”, “ XYZ ”) .getResultList(); TypedQuery <Person> query2 = em.createQuery(jpql , Person. class ); // Set multiple slices as query targets query2.setHint( SlicePersistence.HINT_TARGET , Arrays.asList( new String []{“ One “,” Two ”}); List < Person > result2 = query2.setParameter(“ name ”, “ ABC ”) .getResultList();

38. META-INF/persistence.xml configures a persistence unit <? xml version=&quot; 1.0 &quot; encoding=&quot; UTF-8 &quot;?> < persistence xmlns=&quot; http://java.sun.com/xml/ns/persistence &quot; xmlns:xsi=&quot; http://www.w3.org/2001/XMLSchema-instance &quot; version=&quot; 1.0 &quot; xsi:schemaLocation=&quot; http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd &quot;> < persistence-unit name=&quot; test “ transaction=“ RESOURCE_LOCAL ”> < provider > org.apache.openjpa.persistence.PersistenceProviderImpl </ provider > < class > domain.EntityA </ class > < class > domain.EntityB </ class > < properties > < property name=&quot; openjpa.ConnectionDriverName &quot; value=&quot; com.mysql.jdbc.Driver &quot;/> < property name=&quot; openjpa.ConnectionURL &quot; value=&quot; jdbc:mysql://localhost/test &quot;/> < property name=&quot; openjpa.jdbc.SynchronizeMappings &quot; value=&quot; buildSchema &quot;/> < property name=&quot; openjpa.Log &quot; value=&quot; SQL=TRACE &quot;/> </ properties > </ persistence-unit > List of known Persistent types Vendor-specific configuration Governed by XML Schema JPA Provider is pluggable Identified by Unit Name

47. A complete example of Slice Configuration < properties > < property name=&quot; openjpa.BrokerFactory &quot; value=“ slice &quot;/> < property name=“ openjpa.slice.Names ” value=“ One,Two,Three ”/> < property name=“ openjpa.slice.Master ” value=“ One ”/> < property name=&quot; openjpa.ConnectionDriverName &quot; value=&quot; com.mysql.jdbc.Driver &quot;/> < property name=&quot; openjpa.slice.One.ConnectionURL &quot; value=&quot; jdbc:mysql://mac1:3456/slice1 &quot;/> < property name=“ openjpa.slice.Two.ConnectionURL ” value=“ jdbc:mysql://mac2:5634/slice2 ”/> < property name=“ openjpa.slice.Three.ConnectionDriverName ” value=“ com.ibm.db2.jcc.DB2Driver ”/> < property name=“ openjpa.slice.Three.ConnectionURL ” value=“ jdbc:db2 :// mac3:50000/slice3 ”/> < property name=&quot; openjpa.slice.DistributionPolicy &quot; value=“ acme.org.MyDistroPolicy &quot;/> < property name=&quot; openjpa.jdbc.SynchronizeMappings &quot; value=&quot; buildSchema &quot;/> </ properties > </ persistence-unit > META-INF/persistence.xml Activate Slice Declare slices Configure each slice Configure common behavior Define Data Distribution Policy

51. Core Architectural constructs of OpenJPA EntityManager Factory BrokerFactory EntityManager Broker StoreManager JDBCStore Manager JDBC API OpenJPA Configuration creates creates delegates delegates configured by facade kernel storage POJO + State manager

52. Slice extends OpenJPA by Distributed Template EntityManager Factory BrokerFactory EntityManager Broker DistributedStoreManager JDBCStore Manager JDBC API JDBCStore Manager JDBCStore Manager Distributed Configuration applies Distributed Template Pattern Not aware of partitioned Databases applies Distributed Template Pattern OpenJPA Configuration OpenJPA Configuration OpenJPA Configuration + Slice Moniker facade kernel storage POJO + State manager

56. OpenTrader : OpenJPA/Slice and GWT

57. An example data distribution policy /** * This distribution policy determines the sector of the stock and * picks the slice at ordinal index of the enumerated Sector. */ public class SectorDistributionPolicy implements DistributionPolicy { public String distribute( Object pc, List < String > slices, Object context) { Stock stock = null ; if (pc instanceof Tradable ) { stock = (( Tradable )pc).getStock(); } else if (pc instanceof Stock ) { stock = ( Stock )pc; } else if (pc instanceof Trade ) { stock = (( Trade )pc).getStock(); } else { throw new IllegalArgumentException(“ No policy for “ + pc); } return stock != null ? slices.get(stock.getSector().ordinal()) : null ; } }

58. An example query target policy public static final String MATCH_BID = &quot; select new Match(a,b) from Ask a, Bid b &quot; + &quot; where b = :bid and a.stock.symbol = b.stock.symbol &quot; + &quot; and a.price <= b.price and a.volume >= b.volume &quot; + &quot; and NOT (a.seller = b.buyer) “ + “ and a.trade is NULL and b.trade is NULL &quot;; public class SectorBasedQueryTargetPolicy implements QueryTargetPolicy { public String [] getTargets( String query, Map < Object , Object > params, String language, List < String > slices, Object context) { Stock stock = null ; if (TradingService. MATCH_BID .equals(query)) { stock = ((Tradable)params.get(&quot; bid &quot;)).getStock(); return new String[]{slices.get(stock.getSector().ordinal())}; } return null ; } }

62. Thank You!