I just came across jdbm and am considering using it (or jdbm2) for a project.
I see that jdbm2 was recently forked from jdbm, and is hosted elsewhere (http://code.google.com/p/jdbm2/). However, I couldn't find any mailing list at that location. Is this list the place for jdbm2 questions, or did I miss something? On the subject of jdbm/jdbm2... I need a structured file format which is robust (will not corrupt), and ideally just a single file (since from the user perspective it will be an opaque configuration file that he may want to manipulate -- i.e., backup, copy, move). I see that jdbm can do what I need with 2 files rather than 1, which is actually acceptable (not 100% ideal, but not too bad; on a side note, what is the technical feasibility of stuffing the data and log into a single file, without foregoing corruption-safety). I considered using jdbm2 since it's more active/recent, but when I tried out a simple test I discovered that it creates 8 database files immediately -- ouch, not good. So I'm giving up on jdbm2 for now. Unless jdbm2 can be made to use just 1 or 2 files. Back to jdbm, I wrote a very simple corruption test, and it seemed to run fine for a few hours but finally started throwing Errors. The test consists of (1) a class called CrashTest2 which opens a db, iterates all keys/values, then repeatedly puts random key/value pairs forever (the "domain" of possible keys is limited to 10,000, so puts will eventually overwrite); and (2) a class called Driver which starts the db access class in another process (Runtime.exec()), waits for some random amount of time, then kills the process -- over and over, forever. Stack trace follows: Exception in thread "main" java.lang.Error: CRITICAL: page header magic for block 11603 not OK 0 at jdbm.recman.PageHeader.<init>(PageHeader.java:74) at jdbm.recman.DataPage.<init>(DataPage.java:63) at jdbm.recman.DataPage.getDataPageView(DataPage.java:75) at jdbm.recman.PhysicalRowIdManager.allocNew(PhysicalRowIdManager.java:201) at jdbm.recman.PhysicalRowIdManager.alloc(PhysicalRowIdManager.java:175) at jdbm.recman.PhysicalRowIdManager.insert(PhysicalRowIdManager.java:81) at jdbm.recman.BaseRecordManager.insert(BaseRecordManager.java:225) at jdbm.recman.CacheRecordManager.insert(CacheRecordManager.java:158) at jdbm.recman.CacheRecordManager.insert(CacheRecordManager.java:141) at jdbm.htree.HTree.createInstance(HTree.java:94) at scratch.jdbm.CrashTest2.getTree(CrashTest2.java:52) at scratch.jdbm.CrashTest2.check(CrashTest2.java:66) at scratch.jdbm.CrashTest2.main(CrashTest2.java:42) And the code follows: public class CrashTest2 { private static final String TREE_NAME = "tree"; private static int commitCount; public static void main(String... args) throws Exception { Runtime.getRuntime().addShutdownHook(new Thread() { public void run() { System.out.println(String.format("terminating after approx. %s commits", commitCount)); } }); RecordManager recordManager = RecordManagerFactory.createRecordManager("crashtest2"); long startNanos = System.nanoTime(); check(recordManager); long endNanos = System.nanoTime(); System.out.println(String.format("checked file in %.3fms", (endNanos - startNanos) / 1000000.0)); runTest(recordManager); } private static HTree getTree(RecordManager recordManager, String treeName) throws Exception { long recordId = recordManager.getNamedObject(treeName); if (recordId == 0) { HTree tree = HTree.createInstance(recordManager); recordManager.setNamedObject("htree", tree.getRecid()); return tree; } else { return HTree.load(recordManager, recordId); } } private static void check(RecordManager recordManager) throws Exception { // we're not really checking that everything we expect is here... // we just traverse the entire tree to make sure everything is readable int keyCount = 0; int valueCount = 0; HTree tree = getTree(recordManager, TREE_NAME); FastIterator iter = tree.keys(); String key; while ((key = (String) iter.next()) != null) { keyCount++; String value = (String) tree.get(key); if (value == null) { throw new RuntimeException("null value"); } } iter = tree.keys(); while (iter.next() != null) { valueCount++; } if (keyCount != valueCount) { throw new RuntimeException("expected the same number of keys and values"); } } private static void runTest(RecordManager recordManager) throws Exception { HTree tree = getTree(recordManager, TREE_NAME); Random random = new Random(); while (true) { int key = random.nextInt(10000); tree.put((Integer) key, (Integer) key); recordManager.commit(); commitCount++; } } } public class Driver { private static final Executor executor = Executors.newCachedThreadPool(); public static void main(String... args) throws Exception { String command = "java -classpath build\\classes;lib\\jdbm-1.0.jar scratch.jdbm.CrashTest2"; while (true) { Process process = Runtime.getRuntime().exec(command); drain(process.getInputStream()); drain(process.getErrorStream()); sleepRandomly(200L, 500L); process.destroy(); process.waitFor(); } } private static void drain(final InputStream in) { executor.execute(new Runnable() { public void run() { int c; try { while ((c = in.read()) != -1) { System.out.print((char) c); } } catch(IOException ioe) { ioe.printStackTrace(); } } }); } private static void sleepRandomly(long wait, long range) { final long sleepTime = wait + (long) (Math.random() * range); try { Thread.sleep(sleepTime); } catch(InterruptedException ie) { // do nothing } } } Thanks and regards, Jim ------------------------------------------------------------------------------ This SF.net email is sponsored by Make an app they can't live without Enter the BlackBerry Developer Challenge http://p.sf.net/sfu/RIM-dev2dev _______________________________________________ Jdbm-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/jdbm-general
