OK, so while trying to understand Oracle’s redo latching mechanisms (we have been experiencing a nightmare with log file sync since switching to a new DMX subsystem), I found that java 1.5 has a new Lock class. How cool is that?!!!<\/p>\n
\r\nimport java.io.*;\r\nimport java.util.concurrent.locks.*;\r\nimport java.net.*;\r\nimport java.util.*;\r\n\r\nclass MyThread implements Runnable {\r\n static Lock l = new ReentrantLock();\r\n static Lock lCopy = new ReentrantLock();\r\n static Lock lAllocation = new ReentrantLock();\r\n Thread thrd;\r\n static String logBuff[] = new String[10];\r\n static PrintStream f;\r\n\r\n MyThread(int name){\r\n if (f == null) {\r\n try {\r\n f = new PrintStream(new FileOutputStream(\"\/tmp\/log.log\"),true);\r\n }\r\n catch(Exception e) {\r\n System.out.println(\"Log file does not exist\");\r\n System.exit(1);\r\n }\r\n }\r\n thrd = new Thread(this, name + \"\");\r\n thrd.start(); \/\/ start the thread\r\n }\r\n\r\n private void redoAllocation(String buffVal) {\r\n for (int i = 0; i < 10; i++) {\r\n if (logBuff[i] == null) {\r\n System.out.println(i + \" should be \" + buffVal);\r\n logBuff[i] = buffVal;\r\n }\r\n }\r\n }\r\n\r\n private void redoWrite() {\r\n\r\n }\r\n\r\n private void writeRedo() {\r\n try {\r\n Thread.sleep(3000);\r\n lCopy.lock();\r\n System.out.println(\"Got write lock\");\r\n for (int i = 0; i < 10; i++) {\r\n if (logBuff[i] == null) {\r\n f.println(i + \":\" + logBuff[i]);\r\n }\r\n }\r\n lCopy.unlock();\r\n }\r\n catch(Exception e) {\r\n System.out.println(e);\r\n }\r\n }\r\n\r\n private void redoCopy(String buffVal) {\r\n lCopy.lock();\r\n System.out.println(\"Got copy lock\");\r\n redoAllocation(buffVal);\r\n System.out.println(buffVal);\r\n lCopy.unlock();\r\n writeRedo();\r\n }\r\n\r\n public void run(){\r\n System.out.println(thrd.getName() + \" starting.\");\r\n try {\r\n boolean b = l.tryLock(10000,java.util.concurrent.TimeUnit.MILLISECONDS);\r\n if (b) {\r\n \/\/LGWR should check this latch to see if it has work on which to wait...\r\n \/\/What should we pass? We could just pass the value, and hold the latch for that\r\n \/\/buffer throughout the add process. What did Oracle used to do? You could\r\n \/\/set log_small_buffer_size (or something like that), to encourage it to do more or\r\n \/\/less copies.\r\n System.out.println(\"Got the lock for \" + thrd.getName());\r\n redoCopy((new Date()).toString());\r\n \/\/Now, we need to get the redo allocation latch. This should allocate\r\n \/\/space in the vector. Where should this vector live?\r\n \/\/It should be a static part of this class of a fixed size (like log_buffer).\r\n \/\/The allocation method should identify which block is free, and write to it.\r\n }\r\n else {\r\n System.out.println(\"Didn't get the lock for \" + thrd.getName());\r\n }\r\n \/\/l.lock();\r\n Thread.sleep(2000);\r\n l.unlock();\r\n }\r\n catch(Exception e) {}\r\n System.out.println(thrd.getName() + \" terminating.\");\r\n }\r\n}\r\n\r\nclass myLock {\r\n public static void main(String args[]) {\r\n for (int j = 1; j <= Integer.parseInt(args[0]); j++) {\r\n MyThread mt1 = new MyThread(j);\r\n }\r\n }\r\n}\r\n\r\nclass serveLocks {\r\n static final int PORT = 6666;\r\n static int i = 0;\r\n public static void main(String[] args) throws IOException {\r\n ServerSocket s = new ServerSocket(PORT);\r\n System.out.println(\"Server Started\");\r\n try {\r\n while(true) {\r\n Socket socket = s.accept();\r\n try {\r\n new MyThread(i++);\r\n }\r\n catch(Exception e) {\r\n socket.close();\r\n }\r\n }\r\n }\r\n finally {\r\n s.close();\r\n }\r\n }\r\n}\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"OK, so while trying to understand Oracle’s redo latching mechanisms (we have been experiencing a nightmare with log file sync since switching to a new DMX subsystem), I found that java 1.5 has a new Lock class. How cool is…<\/p>\n