Performance and Clustering of J2EE Applications

Transcription

1 Performance and Clustering of J2EE Applications SWE 645, Fall 2004 Nick Duan 1 Objectives Identify performance problems in J2EE Identify solutions for performance enhancement in development and configuration Understand scalability, reliability and availability in J2EE applications Understand various options in creating a clustered J2EE environment Understand the important design considerations for large-scale applications Nov, 17, 2004 Nick Duan 2 1

2 Performance Issues Is your application capable of handling large number of concurrent user requests? Is your application capable of performing large number of concurrent transactions in a multi-tiered environment? Where is the bottleneck? Web-tier EJB-tier Database-tier Hardware related: CPU, Memory, Network, etc. Nov, 17, 2004 Nick Duan 3 Performance Enhancement and Optimization Who is responsible for doing performance enhancement? Bean Provider: efficient design and coding Deployer: component configuration Container Provider: caching, pooling and bean management Server Provider: communication, clustering Administrator: server tuning, resource configuration and management Nov, 17, 2004 Nick Duan 4 2

3 Performance Enhancement via Design and Coding Web Application Static vs. dynamic content, static vs. dynamic loading, data caching in different scopes, thread safety, database access EJB Application Stateless vs. Stateful session bean, session façade, local interface for entity beans, short transactions, container-managed persistence, batched queries (java.sql.statement) Java Language Primitive vs. Object types, String vs. StringBuffer, Vector vs. ArrayList Nov, 17, 2004 Nick Duan 5 Performance Enhancement via Caching and Pooling Resource Connection Pooling: Live instance cached with the idle state Database, JMS, JCA connectors Web Object Pooling: Not available Web Object Caching: Not configurable EJB Object Pooling: stateless session, entity, and message-driven beans. Bean-specific EJB Object Caching: stateful session and entity beans, in active, idle or passivated state. Bean-specific Nov, 17, 2004 Nick Duan 6 3

4 Configuration via Deploytool Nov, 17, 2004 Nick Duan 7 Configuration via Admin Console Nov, 17, 2004 Nick Duan 8 4

5 Performance Enhancement via Clustering An application is served by a set of homogeneous servers in a distributed enterprise environment (Http servers, servlet engine, EJB servers, database) Transparent to users/clients Scalability, Reliability and Availability (trade-off with performance): Load balancing: distribute work load of the application among multiple machines Failover: if one machine is done, request will be redirected to others Difficult problems: Management of user sessions and business transactions Session persistency and synchronization No change of services during transactions Nov, 17, 2004 Nick Duan 9 Scalability in a Multi-tiered Environment Hardware dependencies (Vertical scaling): Adding more hardware Software dependencies (Horizontal scaling): Server clustering: Running applications on multiple servers or server instances: Web servers, application servers, database servers Typical components for clustering in a multitiered environment: Web server, web application server/ejb server/app server, and database server Each tier in front (client) dispatches request to tier in the back (cluster of services) Nov, 17, 2004 Nick Duan 10 5

6 Clustering of Web Application Servers Simple type: Dispatcher with a set of independent servers. Request of clients redirected by the dispatcher to individual servers via Http Redirect Complex type: Federation of tightly integrated machine Star topology with centralized load balancer/controller Hardware LB: CISCO content-based switch Software LB: Apache Tomcat, JNDI server Networked topology with distributed control: everyone keeps a session copy of everyone else Nov, 17, 2004 Nick Duan 11 Clustering with Tomcat Works in conjunction with the Apache Web server Multiple instances of Tomcat can be initiated during startup to form a cluster Load balancer is defined by the JK adapter, responsible for dispatching requests to workers and maintaining sticky user sessions Requests are scheduled and distributed using weighted Round-Robin Configuration defined in the workers.properties file under /conf directory Nov, 17, 2004 Nick Duan 12 6

7 Tomcat Clustering with Apache HTTP Server Aoache Web Server JK Module with built-in LB Tomcat 1 Tomcat 2 File System/ Database Tomcat 3 Nov, 17, 2004 Nick Duan 13 Design Factors in a Clustering Environment Session Management Sticky Sessions: LB will forward the requests of the same user session to the same worker Session Replication and Persistency: Replicating sessions attributes and other information, e.g. login, time out, security, etc. Vendor/application specific Database File System In-memory Implement Serializable to ensure session persistency Use transaction services Nov, 17, 2004 Nick Duan 14 7

8 Clustering of EJB Servers Clustering logic/load-balancing algorithm: How to locate and select an EJB Service for a request Round robin, least-recently used, not-recently used Type of dispatch control for load-balancing (LB) and fail-over (FV) Client-directed, service locator pattern JNDI-directed Container-directed Home stub Remote stub Nov, 17, 2004 Nick Duan 15 Clustering of different EJB types Stateless session: most scalable bean types LB on both home and remote component methods. FV on home but not all remote methods Stateful session: session replication required LB on home but not remote component methods. FV on only idempotent home and remote methods Entity: possible but not recommended LB on both home and remote methods, FV on idempotent methods. Caching is a problem Message-driven: relies on JMS clustering, inherently scalable Nov, 17, 2004 Nick Duan 16 8

9 Summary Performance of J2EE applications is affected by design decisions, coding, configuration and administration Multiple J2EE app servers can be arranged in a cluster environment to achieve Scalability, reliability and availability (trade-off with performance) Load balancing Failover Special consideration for session/transaction management in a cluster environment Nov, 17, 2004 Nick Duan 17 Quiz What techniques to use to enhance the performance of J2EE applications? What tasks is a LB responsible for and what types of load balancers are commonly used for web apps? What pros and cons of using in-memory session replication vs. file-based session replication? Why clustering of entity bean containers makes little sense? What should I do to ensure servlets and stateful session beans capable for session replication? Nov, 17, 2004 Nick Duan 18 9