Web logic classes in mumbai
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The document discusses transaction management in BEA WebLogic Server 6.0, highlighting its capabilities for ensuring data integrity in distributed environments and support for various resource types. It details the transaction model, including attributes like atomicity, consistency, isolation, and durability, as well as timeout handling, rollback mechanisms, and multi-server participation. Additionally, it outlines programming interfaces for transaction management, optimizations, and best practices for monitoring and configuring transactions.
Web logic classes in mumbai
- 2. Why use transactions? What capabilities does BEA WebLogic Server 6.0 provide? How to program? How to configure and monitor? References Questions & Answers
- 3. Ensure data integrity when accessing more than one data store, especially in distributed environment Simple model for application programmer: AA - atomic CC - consistent II - isolated DD - durable
- 4. A transaction is a higher-level unit of work than a database query or an object invocation BEA WebLogic Server allows transactions to be given a semantic name (“TransferFunds” or “ReserveSeat” or “CheckOut”) Transaction Name is reported in error messages Statistics subtotals categorized by Transaction Name
- 5. Transactions are subject to timeout 30 second default Application code (or the EJB container) can mark a transaction “rollback only” In an overloaded system, BEA WebLogic Server: Times out requests (who waits 30+ seconds for a Web page to return?) Avoids wasted work on “doomed” transactions Eventually refuses to begin new transactions when there are too many already running (configurable parameter)
- 6. Multiple servers may participate in a distributed transaction Clustered or non-clustered Need not be in same administrative domain Requires connectivity and permissions Clients may initiate transactions and infect multiple servers Commit responsibility is handed off to a server Clients may not enlist resources or register synchronization callbacks Multiple XA resources may participate in same transaction More than one coordinated by “two-phase commit” algorithm
- 7. JDBC Recognized any JDBC driver that implements JDBC 2.0 XA extensions BEA provides Type 2 XA driver for Oracle 8.1.6 client JDBC wrapper enhances performance JMS Supports XA, can participate in JTA transactions All storage types: database, file, non-persistent EJB Automatically manages transactions based on EJB’s deployment descriptor
- 8. Transaction Manager XA-Capable Resource EJB Container Application JDBC JTA Wrapper JDBC JMS XA JDBC JTA
- 9. Boxcar algorithm for multiple commit records per I/O One-phase commit optimization Read-only branch optimization Dynamic resource enlistment optimization Piggy-back transaction propagation Multiple operations per coordination message Asynchronous, parallel coordination architecture with retry
- 10. Good news! In many cases, transactions are controlled by the EJB Container, and an application programmer writes no code for transactions The UserTransaction object provides simple begin/commit/rollback functionality for applications that need to explicitly demarcate transaction boundaries More powerful transaction objects normally used by the Application Server and EJB Container are available to applications with complex transactional requirements BEA WebLogic Server extensions for convenience and added value
- 11. UserTransaction Basic methods to begin, commit, rollback transactions and get/set status TransactionManager Adds suspend, resume, get thread’s current Transaction object Transaction Represents on transaction, controls enlistment and synchronization Synchronization Callback interface for before/after completion notification XAResource Xid Various exceptions and status codes
- 12. weblogic.transaction.TxHelper Static methods to get Transaction, UserTransaction, and TransactionManager objects weblogic.transaction.Transaction Get/set transaction name, transaction properties Get/set rollback reason Get timeout information Get Xid weblogic.transaction.TransactionManager XA resource registration Get transaction object by Xid Force suspend/resume (without XA calls)
- 13. Transaction Timeout Seconds Default number of seconds for transaction timeout, unless overridden by API call or EJB container Abandon Timeout Seconds After X number of seconds, stop trying to resolve branch(es) of a committed transaction and log an error Should never happen unless resource dies during commit processing and does not come back Forget Heuristics When resource reports a heuristic completion, log an error message and then tell resource to “forget”about that transaction
- 14. Before Completion Iteration Limit Maximum number of times a server will iterate through registered Synchronization objects for the same transaction Prevents infinite loops when one Synchronization callback causes another Synchronization object registration Max Transactions Maximum number of transactions that can be simultaneously active on a server Max Unique Name Statistics Maximum number of transaction names remembered for categorizing statistic subtotals
- 16. Transaction Log File Prefix Each server that coordinates a two-phase commit transaction writes to the transaction log at commit time and reads the transaction log during crash recovery A transaction log is stored in multiple files Space is reclaimed automatically Never delete these files Default location is server’s current directory Highly reliable file system is recommended (RAID, etc.) File naming convention: Prefix + ServerName + 9999 + “.tlog” (9999 = unique number)
- 17. Transaction branches Connection pool name determines transaction branch qualifier Different pool names cause separate branches, even if connected to same database Databases typically provide lock isolation between branches, shared locks within a branch Benefits of multiple branches: Lock isolation protects independently developed components from unexpected cross-interference Drawbacks of multiple branches: Lock conflicts can cause deadlock/timeout More overhead in transaction coordination, more XA calls
- 18. JDBCTxDataSource wrapper for non-XA database drivers If EnableTwoPhaseCommit=“false” (the default) and a non-XA JDBC driver is supplied, commit() will fail unless this is the only transaction participant If EnableTwoPhaseCommit=“true” a non-XA JDBC driver may participate in a transaction with multiple participants, however there is a risk that the non-XA driver might fail at commit time This is reported as a heuristic rollback exception
- 19. Counters Overall Subtotal by XAResource Subtotal by Transaction name Specific transactions List transactions more than XX seconds old “Old” transactions are the most interesting ones
- 24. Ongoing integration testing and cooperation with XA resource providers Support for transaction export/import to/from external systems via interposed gateway architecture Additional internal enhancements for reliability, overload tolerance, and performance Additional management, monitoring, statistics
- 25. Specifications http://www.java.sun.com/products/jta http://www.java.sun.com/j2ee BEA WebLogic Server 6.0 Documentation http://e-docs.bea.com News Group news://newsgroups.bea.com/weblogic.develope r.interest.transaction