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	Transactional Programming Episode One II See Once See Good 20150431 Here we present a program to accomplish some tasks sequentially. But these tasks may fail at a un-noticeable rate and may throw a run-time exception so halt the executing program. package net.heteroclinic.tp; import java.util.Random; /* Science and technology promotion license. Read www.heteroclinic.net for details. Zhikai Wang www.heteroclinic.net 2015 / public class CatchMeNot { //static protected final Random rand = new Random(); static public class Task { // The task may fail at a one against iHaveAFailureRate rate. protected final int iHaveAFailureRate; public static final int FAILURE_RATE_CEILING = 50; public static final int FAILURE_RATE_FLOOR = 10; public Task() { iHaveAFailureRate =(int) (Math.random()( (double)(FAILURE_RATE_CEILING - FAILURE_RATE_FLOOR +1 ) )) +FAILURE_RATE_FLOOR; } public void doJob(String job) { int dice = (int) (Math.random()*(double)Integer.MAX_VALUE); System.out.printf("dice=%d iHaveAFailureRate=%d\n",dice,iHaveAFailureRate); if (dice % iHaveAFailureRate == 0) { throw new RuntimeException("Sorry, got to pick the kid."); } System.out.println("High five on "+job+"."); } } public static void main(String[] args) { Task task1 = new Task(); Task task2 = new Task();; Task task3 = new Task();; task1.doJob("Job 1"); task2.doJob("Job 2"); task3.doJob("Job 3"); System.out.println("Eod pck"); } }
	Transactional Programming Episode One II Stress Causes Exceptions 20150430 Stress may cause exceptions, hang on, I would rather say stress reveals what is hidden, for a program (or something else?). Repeating many times shows the true color not addressing for philosophy. When I am wring a program. The next thing after the first run, is to run it a hundred times more. Normally, I would get something out of expectation. In CatchMeNot, only a large number of running cases may hit the run-time error. So we seek a solution when reliability is a concern. package net.heteroclinic.tp; /* Science and technology promotion license. Read www.heteroclinic.net for details. Zhikai Wang www.heteroclinic.net 2015 */ public class ALotOfDays { public static void main(String[] args) { final int howManyYouConsiderMany = CatchMeNot.Task.FAILURE_RATE_CEILING ^ 3; for (int i = 0; i<howManyYouConsiderMany; i++ ) { System.out.println(i); CatchMeNot.main(new String []{}); } } }
	Transactional Programming Episode One III Sliding Window Protocol 20150430 The sliding window protocol is used in network data transmission for reliable in-order delivery. Here we don't go into details in this episode. What we learn from this protocol, is that first, if we fail at one step of an operation, we can roll back. The design philosophy is, we will handle all exceptions, we don't mind what exception we have to handle, but we will roll back to the starting point. Depends on the relationship of the sequential steps, we may choose re-do all or just re-do one step in question. References: baike.baidu.com/view/1199185.htm http://en.wikipedia.org/wiki/Sliding_window_protocol
	Transactional Programming Episode One IV A Simply Rolling Back Example 20150430 We showed CatchMeNot's design fallacy. One party as the jober may concern "job 3" is done for "howManyYouConsiderMany". Another party as the jobee may concern "Eod pck". There will be exceptions that may affect the mutual goal (at the least the intersection shares a chunk of common interests). We use roll-back-to-start, handle all exceptions and ignore the exceptions' types. So the program can run many days without a halt. . package net.heteroclinic.tp; /* Science and technology promotion license. Read www.heteroclinic.net for details. Zhikai Wang www.heteroclinic.net 2015 / import net.heteroclinic.tp.CatchMeNot.Task; public class BackRollable extends CatchMeNot{ public static void main(String[] args) { Task task1 = new Task(); Task task2 = new Task(); Task task3 = new Task(); final int howManyYouConsiderMany = CatchMeNot.Task.FAILURE_RATE_CEILING CatchMeNot.Task.FAILURE_RATE_CEILING; for (int i = 0; i<howManyYouConsiderMany; ) { System.out.println(i); boolean task1Done = false; boolean task2Done = false; boolean task3Done = false; if (!task1Done ) { try { task1.doJob("job 1"); task1Done = true; } catch (Exception e) { task1Done = false; continue; } } if (!task2Done ) { try { task2.doJob("job 2"); task2Done = true; } catch (Exception e) { task2Done = false; continue; } } if (!task3Done ) { try { task3.doJob("job 3"); task3Done = true; } catch (Exception e) { task2Done = false; continue; } } System.out.println("Eod pck of day no."+(++i)); } } }