From 2c3748324ded5ae7b0bd7c93b067af87846ece63 Mon Sep 17 00:00:00 2001
From: "Brian S. O'Neill" <bronee@gmail.com>
Date: Sat, 19 Mar 2011 19:42:53 +0000
Subject: Add TransactionMonitor.

---
 .../amazon/carbonado/txn/TransactionManager.java   | 24 ++++++++++-
 .../amazon/carbonado/txn/TransactionMonitor.java   | 47 ++++++++++++++++++++++
 .../com/amazon/carbonado/txn/TransactionScope.java | 22 ++++++++--
 3 files changed, 89 insertions(+), 4 deletions(-)
 create mode 100644 src/main/java/com/amazon/carbonado/txn/TransactionMonitor.java

(limited to 'src/main/java/com')

diff --git a/src/main/java/com/amazon/carbonado/txn/TransactionManager.java b/src/main/java/com/amazon/carbonado/txn/TransactionManager.java
index dcd9671..19aec4d 100644
--- a/src/main/java/com/amazon/carbonado/txn/TransactionManager.java
+++ b/src/main/java/com/amazon/carbonado/txn/TransactionManager.java
@@ -39,15 +39,21 @@ public abstract class TransactionManager<Txn> {
 
     private final ThreadLocal<TransactionScope<Txn>> mLocalScope;
     private final Map<TransactionScope<Txn>, ?> mAllScopes;
+    private final TransactionMonitor mMonitor;
 
     private int mState;
 
     public TransactionManager() {
+        this(null);
+    }
+ 
+    public TransactionManager(TransactionMonitor monitor) {
         mLocalScope = new ThreadLocal<TransactionScope<Txn>>();
         mAllScopes = new WeakIdentityMap();
+        mMonitor = monitor;
     }
 
-    /**
+   /**
      * Returns the thread-local TransactionScope, creating it if needed.
      */
     public TransactionScope<Txn> localScope() {
@@ -108,6 +114,22 @@ public abstract class TransactionManager<Txn> {
         return false;
     }
 
+    // Called by TransactionScope.
+    void entered(Transaction txn, Transaction parent) {
+        TransactionMonitor monitor = mMonitor;
+        if (monitor != null) {
+            monitor.entered(txn, parent);
+        }
+    }
+
+    // Called by TransactionScope.
+    void exited(Transaction txn, Transaction active) {
+        TransactionMonitor monitor = mMonitor;
+        if (monitor != null) {
+            monitor.exited(txn, active);
+        }
+    }
+
     /**
      * Closes all transaction scopes. Should be called only when repository is
      * closed.
diff --git a/src/main/java/com/amazon/carbonado/txn/TransactionMonitor.java b/src/main/java/com/amazon/carbonado/txn/TransactionMonitor.java
new file mode 100644
index 0000000..2604dac
--- /dev/null
+++ b/src/main/java/com/amazon/carbonado/txn/TransactionMonitor.java
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2011 Amazon Technologies, Inc. or its affiliates.
+ * Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
+ * of Amazon Technologies, Inc. or its affiliates.  All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.amazon.carbonado.txn;
+
+import com.amazon.carbonado.Transaction;
+
+/**
+ * Is notified as transactions enter and exit. Implementation must be thread-safe.
+ *
+ * @author Brian S O'Neill
+ * @see TransactionManager
+ */
+public interface TransactionMonitor {
+    /**
+     * Called by a thread which has just entered a transaction.
+     *
+     * @param entered transaction just entered
+     * @param parent optional parent of transaction; is null for top level transactions
+     */
+    public abstract void entered(Transaction entered, Transaction parent);
+
+    /**
+     * Called by a thread which has just exited a transaction. Only the first
+     * invocation of the exit method is passed to this monitor.
+     *
+     * @param exited transaction just exited
+     * @param active optional transaction which is now active; is null if the
+     * outermost transaction scope exited
+     */
+    public abstract void exited(Transaction exited, Transaction active);
+}
diff --git a/src/main/java/com/amazon/carbonado/txn/TransactionScope.java b/src/main/java/com/amazon/carbonado/txn/TransactionScope.java
index 7cf4903..2110ff6 100644
--- a/src/main/java/com/amazon/carbonado/txn/TransactionScope.java
+++ b/src/main/java/com/amazon/carbonado/txn/TransactionScope.java
@@ -90,7 +90,12 @@ public class TransactionScope<Txn> {
                 }
             }
 
-            return mActive = new TransactionImpl<Txn>(this, parent, false, actualLevel);
+            TransactionImpl<Txn> txn = new TransactionImpl<Txn>(this, parent, false, actualLevel);
+            mActive = txn;
+
+            mTxnMgr.entered(txn, parent);
+
+            return txn;
         } finally {
             mLock.unlock();
         }
@@ -113,12 +118,23 @@ public class TransactionScope<Txn> {
                     ("Desired isolation level not supported: " + level);
             }
 
-            return mActive = new TransactionImpl<Txn>(this, mActive, true, actualLevel);
+            TransactionImpl<Txn> txn = new TransactionImpl<Txn>(this, mActive, true, actualLevel);
+            mActive = txn;
+
+            mTxnMgr.entered(txn, null);
+
+            return txn;
         } finally {
             mLock.unlock();
         }
     }
 
+    // Called by TransactionImpl with lock held.
+    void exited(TransactionImpl<Txn> txn, TransactionImpl<Txn> active) {
+        mActive = active;
+        mTxnMgr.exited(txn, active);
+    }
+
     /**
      * Registers the given cursor against the active transaction, allowing it
      * to be closed on transaction exit or transaction manager close. If there
@@ -494,8 +510,8 @@ public class TransactionScope<Txn> {
                         }
                     }
                 } finally {
-                    scope.mActive = mParent;
                     mState = EXITED;
+                    scope.exited(this, mParent);
                     if (exception != null) {
                         throw ExceptionTransformer.getInstance().toPersistException(exception);
                     }
-- 
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