Merge pull request #669 from renebock/concurrency

Concurrency

Frameworks/Core/ERExtensions/Sources/er/extensions/concurrency/ERXLongResponseTask.java

@@ -7,6 +7,9 @@
 
 import com.webobjects.appserver.WOApplication;
 import com.webobjects.appserver.WOComponent;
+import com.webobjects.eocontrol.EOEditingContext;
+import com.webobjects.eocontrol.EOObjectStore;
+import com.webobjects.eocontrol.EOObjectStoreCoordinator;
 import com.webobjects.foundation.NSArray;
 import com.webobjects.foundation.NSForwardException;
 import com.webobjects.foundation.NSMutableArray;
@@ -86,7 +89,9 @@ public static NSArray tasks() {
 	}
 
 	public abstract class DefaultImplementation implements Runnable, ERXLongResponseTask {
-
+		private volatile EOObjectStore _parentObjectStore;
+		private Long _taskEditingContextTimestampLag;
+
 
 		/** logging support */
 		public Logger log = Logger.getLogger(ERXUtilities.class);
@@ -344,5 +349,92 @@ public WOComponent nextPage() {
 		 */
 		public abstract Object performAction();
 
+		//---------------------- Copied from ERXTask -------------------------------------
+
+		/**
+		 * See Effective Java item #71 for explanation of this threadsafe lazy
+		 * initialization technique
+		 *
+		 * @return the parent, usually an {@link EOObjectStoreCoordinator} to
+		 *         partition the task's EOF intensive work form the rest of the app.
+		 */
+		protected final EOObjectStore parentObjectStore() {
+			EOObjectStore osc = _parentObjectStore;
+			if (osc == null) {
+				synchronized (this) {
+					osc = _parentObjectStore;
+					if (osc == null) {
+						_parentObjectStore = osc = ERXTaskObjectStoreCoordinatorPool.objectStoreCoordinator();
+					}
+				}
+			}
+			return osc;
+		}
+
+		/**
+		 * @param parentObjectStore
+		 *            the parent, usually an {@link EOObjectStoreCoordinator} to
+		 *            partition the task's EOF intensive work from the rest of the
+		 *            app. If you are going to manually set this, you should do it
+		 *            before starting the task.
+		 */
+		public final synchronized void setParentObjectStore(EOObjectStore parentObjectStore) {
+			_parentObjectStore = parentObjectStore;
+		}
+
+		/**
+		 * <strong>You must manually lock and unlock the editing context returned by
+		 * this method.</strong> It is not recommended that you depend on auto
+		 * locking in background threads.
+		 * 
+		 * Even though this method currently returns an auto-locking EC if
+		 * auto-locking is turned on for the app, a future update is planned that
+		 * will return a manually locking EC from this method even if auto-locking
+		 * is turned on for regular ECs used in normal request-response execution.
+		 * 
+		 * @return a new EOEditingContext.
+		 */
+		protected EOEditingContext newEditingContext() {
+			EOEditingContext ec = ERXEC.newEditingContext(parentObjectStore());
+			// if this is not a nested EC, we can set the fetch time stamp
+			if (!(parentObjectStore() instanceof EOEditingContext)) {
+				ec.setFetchTimestamp(taskEditingContextTimestampLag());
+			}
+			return ec;
+		}
+
+		/**
+		 * By design EOEditingContext's have a fetch timestamp (default is 1 hour)
+		 * that effectively creates an in-memory caching system for EOs. This works
+		 * great for users browsing through pages in the app. However, experience
+		 * has shown that background EOF tasks are performing updates based on the
+		 * state of other EOs, and thus we want to This is a long-running task. The
+		 * last thing I want to do is perform a long running task with stale EOs, so
+		 * we lazily create a fetch timestamp of the current time when we create the
+		 * first EC and thus ensure fresh data. Secondly, we continue, by default to
+		 * use this timestamp for the duration of the task since experience has
+		 * shown that by doing so we can prevent unnecessary database fetching
+		 * especially when our task is adding lots of items to a single relationship
+		 * in batches.
+		 * 
+		 * However if you want fresh data each time you create an EC in your task,
+		 * feel free to set the fetch time stamp to the current time in your task
+		 * each time you create a new EC.
+		 * 
+		 * For R-R ec's we prefer fresh data on new pages. However for long running
+		 * tasks, it is often best pick a single point in time, usually when the
+		 * first ec is created as the timestamp lag. This works well when we are
+		 * iterating and making new ec's especially if we are adding 100's of items
+		 * to a relationship and cycling ec's
+		 * 
+		 * @return the timestamp lag to use for new ec's created in the task thread.
+		 */
+		protected long taskEditingContextTimestampLag() {
+			if (_taskEditingContextTimestampLag == null) {
+				_taskEditingContextTimestampLag = Long.valueOf(System.currentTimeMillis());
+			}
+			return _taskEditingContextTimestampLag.longValue();
+		}
+
 	}
 }

Frameworks/Core/ERExtensions/Sources/er/extensions/concurrency/ERXTask.java

@@ -150,7 +150,7 @@ protected EOEditingContext newEditingContext() {
 	 * 
 	 * @return the timestamp lag to use for new ec's created in the task thread.
 	 */
-	private long taskEditingContextTimestampLag() {
+	protected long taskEditingContextTimestampLag() {
 		if (_taskEditingContextTimestampLag == null) {
 			_taskEditingContextTimestampLag = Long.valueOf(System.currentTimeMillis());
 		}

Frameworks/Core/ERExtensions/Sources/er/extensions/concurrency/ERXWOLongResponsePage.java

@@ -3,9 +3,13 @@
 import com.webobjects.appserver.WOApplication;
 import com.webobjects.appserver.WOComponent;
 import com.webobjects.appserver.WOContext;
+import com.webobjects.eocontrol.EOEditingContext;
+import com.webobjects.eocontrol.EOObjectStore;
+import com.webobjects.eocontrol.EOObjectStoreCoordinator;
 import com.webobjects.woextensions.WOLongResponsePage;
 
 import er.extensions.appserver.ERXApplication;
+import er.extensions.eof.ERXEC;
 
 /**
  * ERXWOLongResponsePage is just like WOLongResponsePage except that it
@@ -21,6 +25,9 @@ public abstract class ERXWOLongResponsePage extends WOLongResponsePage {
 	 * <a href="http://java.sun.com/j2se/1.4/pdf/serial-spec.pdf">Java Object Serialization Spec</a>
 	 */
 	private static final long serialVersionUID = 1L;
+	private volatile EOObjectStore _parentObjectStore;
+	private Long _taskEditingContextTimestampLag;
+
 
 	public ERXWOLongResponsePage(WOContext context) {
 		super(context);
@@ -44,4 +51,92 @@ public void run() {
 			ERXApplication._endRequest();
 		}
 	}
+
+	//---------------------- Copied from ERXTask -------------------------------------
+
+	/**
+	 * See Effective Java item #71 for explanation of this threadsafe lazy
+	 * initialization technique
+	 * 
+	 * @return the parent, usually an {@link EOObjectStoreCoordinator} to
+	 *         partition the task's EOF intensive work form the rest of the app.
+	 */
+	protected final EOObjectStore parentObjectStore() {
+		EOObjectStore osc = _parentObjectStore;
+		if (osc == null) {
+			synchronized (this) {
+				osc = _parentObjectStore;
+				if (osc == null) {
+					_parentObjectStore = osc = ERXTaskObjectStoreCoordinatorPool.objectStoreCoordinator();
+				}
+			}
+		}
+		return osc;
+	}
+
+	/**
+	 * @param parentObjectStore
+	 *            the parent, usually an {@link EOObjectStoreCoordinator} to
+	 *            partition the task's EOF intensive work from the rest of the
+	 *            app. If you are going to manually set this, you should do it
+	 *            before starting the task.
+	 */
+	public final synchronized void setParentObjectStore(EOObjectStore parentObjectStore) {
+		_parentObjectStore = parentObjectStore;
+	}
+
+	/**
+	 * <strong>You must manually lock and unlock the editing context returned by
+	 * this method.</strong> It is not recommended that you depend on auto
+	 * locking in background threads.
+	 * 
+	 * Even though this method currently returns an auto-locking EC if
+	 * auto-locking is turned on for the app, a future update is planned that
+	 * will return a manually locking EC from this method even if auto-locking
+	 * is turned on for regular ECs used in normal request-response execution.
+	 * 
+	 * @return a new EOEditingContext.
+	 */
+	protected EOEditingContext newEditingContext() {
+		EOEditingContext ec = ERXEC.newEditingContext(parentObjectStore());
+		// if this is not a nested EC, we can set the fetch time stamp
+		if (!(parentObjectStore() instanceof EOEditingContext)) {
+			ec.setFetchTimestamp(taskEditingContextTimestampLag());
+		}
+		return ec;
+	}
+
+	/**
+	 * By design EOEditingContext's have a fetch timestamp (default is 1 hour)
+	 * that effectively creates an in-memory caching system for EOs. This works
+	 * great for users browsing through pages in the app. However, experience
+	 * has shown that background EOF tasks are performing updates based on the
+	 * state of other EOs, and thus we want to This is a long-running task. The
+	 * last thing I want to do is perform a long running task with stale EOs, so
+	 * we lazily create a fetch timestamp of the current time when we create the
+	 * first EC and thus ensure fresh data. Secondly, we continue, by default to
+	 * use this timestamp for the duration of the task since experience has
+	 * shown that by doing so we can prevent unnecessary database fetching
+	 * especially when our task is adding lots of items to a single relationship
+	 * in batches.
+	 * 
+	 * However if you want fresh data each time you create an EC in your task,
+	 * feel free to set the fetch time stamp to the current time in your task
+	 * each time you create a new EC.
+	 * 
+	 * For R-R ec's we prefer fresh data on new pages. However for long running
+	 * tasks, it is often best pick a single point in time, usually when the
+	 * first ec is created as the timestamp lag. This works well when we are
+	 * iterating and making new ec's especially if we are adding 100's of items
+	 * to a relationship and cycling ec's
+	 * 
+	 * @return the timestamp lag to use for new ec's created in the task thread.
+	 */
+	protected long taskEditingContextTimestampLag() {
+		if (_taskEditingContextTimestampLag == null) {
+			_taskEditingContextTimestampLag = Long.valueOf(System.currentTimeMillis());
+		}
+		return _taskEditingContextTimestampLag.longValue();
+	}
+
 }