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It s easy enough to fix the problem on a single system, but why not write a test routine that you run server-side first A routine to verify that the remote system s clock is within an acceptable range We have actually been writing such tests as we go along, especially in chapters 12 and 13 All of our server-side happiness tests, implemented in our JSP <happy> tag and JSPs and tested through HttpUnit, are in fact regression tests for configuration issues we have encountered With Ant we can build, deploy, and run these regression tests every time we build and deploy our service This does not mean that the tests are easy to write; a web service we were working on had some tests that took whole days to write and validate.

Session session = getSessionFactory().openSession(); session.setFlushMode(FlushMode.MANUAL); // First step in the conversation session.beginTransaction(); Item item = (Item) session.get(Item.class, new Long(123) ); session.getTransaction().commit(); // Second step in the conversation session.beginTransaction(); Item newItem = new Item(); Long newId = (Long) session.save(newItem); // Triggers INSERT! session.getTransaction().commit(); // Roll back the conversation! session.close();

You may expect that the whole conversation, the two steps, can be rolled back by closing the unflushed persistence context. The insertion of the newItem is supposed to be delayed until you call flush() on the Session, which never happens in this code. This is the case only if you don t pick identity or select as your identifier generator. With these generators, an INSERT must be executed in the second step of the conversation, and the INSERT is committed to the database. One solution uses compensation actions that you execute to undo any possible insertions made during a conversation that is aborted, in addition to closing the unflushed persistence context. You d have to manually delete the row that was inserted. Another solution is a different identifier generator, such as a sequence, that supports generation of new identifier values without insertion. The persist() operation exposes you to the same problem. However, it also provides an alternative (and better) solution. It can delay insertions, even with post-insert identifier generation, if you call it outside of a transaction:

Yet just as the benefit of unit tests grows over time, the value of having tests to validate the server configuration and operations use cases grows over the operational lifespan of the service As a successful service should run for much longer than its development time takes, these tests do pay for themselves 437.

Session session = getSessionFactory().openSession(); session.setFlushMode(FlushMode.MANUAL); // First step in the conversation session.beginTransaction(); Item item = (Item) session.get(Item.class, new Long(1)); session.getTransaction().commit(); // Second step in the conversation Item newItem = new Item(); session.persist(newItem); // Roll back the conversation! session.close();

Operations defect tracking If you have use cases and regression tests, you need to round everything off with defect tracking. A web server running Scarab (from tigris.org) or bugzilla (http:// www.mozilla.org/projects/bugzilla/) should suffice. For the defect tracking database to be useful, all the symptoms of the problems must be noted, such as throughput a quarter of that expected, along with the cause, accidental use of CAT-3 LAN cable, and the fix, replaced with new CAT-5 cable. This is all obvious stuff. What is essential is that you do not wait until the system is in staging before you start creating this database: the defect tracking should begin the moment you first start bringing up the first version of the application on your local server. The developers, through building and deploying a service many times a day, gain more early experience in the issues than anyone else does. This knowledge needs to be stored in the defect tracking system unless they want to carry the pager every weekend. Integrating operations with the build process The obvious implication of the previous ideas is that the operations team needs to be involved early. You cannot build a system and then just hand it off for delivery. There is no room for the waterfall model in modern software development processes, and we must prevent the final stage of the project, deployment, from taking on the look and feel of the waterfall. We all know the waterfall doesn t work. It isn t flexible or responsive, which is why modern processes abhor it. Yet, as figure 18.1 shows, it is still there.