From 4b0854c2bb835322bb6da96ec0b80ad8b1723b57 Mon Sep 17 00:00:00 2001
From: "Brian S. O'Neill" <bronee@gmail.com>
Date: Sun, 4 Apr 2010 01:28:51 +0000
Subject: Fix race condition which causes layout generation to be lost.

---
 .../java/com/amazon/carbonado/layout/Layout.java   | 27 +++++++++++++++++-----
 .../com/amazon/carbonado/layout/LayoutFactory.java |  6 +++++
 .../amazon/carbonado/layout/LayoutProperty.java    | 20 +++++++++++-----
 3 files changed, 41 insertions(+), 12 deletions(-)

(limited to 'src/main/java')

diff --git a/src/main/java/com/amazon/carbonado/layout/Layout.java b/src/main/java/com/amazon/carbonado/layout/Layout.java
index 1ea9a36..0c7ab83 100644
--- a/src/main/java/com/amazon/carbonado/layout/Layout.java
+++ b/src/main/java/com/amazon/carbonado/layout/Layout.java
@@ -25,6 +25,7 @@ import java.net.InetAddress;
 import java.net.UnknownHostException;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
@@ -45,6 +46,7 @@ import com.amazon.carbonado.Query;
 import com.amazon.carbonado.RepositoryException;
 import com.amazon.carbonado.Storable;
 import com.amazon.carbonado.SupportException;
+import com.amazon.carbonado.UniqueConstraintException;
 import com.amazon.carbonado.info.StorableInfo;
 import com.amazon.carbonado.info.StorableProperty;
 import com.amazon.carbonado.synthetic.SyntheticKey;
@@ -484,7 +486,8 @@ public class Layout {
             return true;
         }
         return getStorableTypeName().equals(layout.getStorableTypeName())
-            && getAllProperties().equals(layout.getAllProperties());
+            && getAllProperties().equals(layout.getAllProperties())
+            && Arrays.equals(mStoredLayout.getExtraData(), layout.mStoredLayout.getExtraData());
     }
 
     /**
@@ -519,20 +522,32 @@ public class Layout {
         if (mAllProperties == null) {
             throw new IllegalStateException();
         }
+
         mStoredLayout.setGeneration(generation);
-        if (!mStoredLayout.tryInsert()) {
-            StoredLayout existing = mLayoutFactory.mLayoutStorage.prepare();
+
+        try {
+            mStoredLayout.insert();
+        } catch (UniqueConstraintException e) {
+            // If existing record logically matches, update to allow replication.
+            StoredLayout existing = mStoredLayout.prepare();
             mStoredLayout.copyPrimaryKeyProperties(existing);
             try {
                 existing.load();
-            } catch (FetchException e) {
-                throw e.toPersistException();
+            } catch (FetchException e2) {
+                throw e2.toPersistException();
+            }
+            if (existing.getGeneration() != generation ||
+                !existing.getStorableTypeName().equals(getStorableTypeName()) ||
+                !Arrays.equals(existing.getExtraData(), mStoredLayout.getExtraData()))
+            {
+                throw e;
             }
             mStoredLayout.setVersionNumber(existing.getVersionNumber());
             mStoredLayout.update();
         }
+
         for (LayoutProperty property : mAllProperties) {
-            property.store();
+            property.insert();
         }
     }
 }
diff --git a/src/main/java/com/amazon/carbonado/layout/LayoutFactory.java b/src/main/java/com/amazon/carbonado/layout/LayoutFactory.java
index c82e3b4..92099dd 100644
--- a/src/main/java/com/amazon/carbonado/layout/LayoutFactory.java
+++ b/src/main/java/com/amazon/carbonado/layout/LayoutFactory.java
@@ -184,6 +184,12 @@ public class LayoutFactory implements LayoutCapability {
                     // If this point is reached, then type represents a new
                     // generation. Calculate next generation value and insert.
 
+                    // Note: The following query might find a record that
+                    // didn't exist just a moment ago. This will cause a new
+                    // generation value to be calculated, which is incorrect.
+                    // Inserting the layout causes a unique constraint
+                    // exception, which prevents the mistake from persisting.
+
                     assert(newLayout != null);
                     int generation = 0;
 
diff --git a/src/main/java/com/amazon/carbonado/layout/LayoutProperty.java b/src/main/java/com/amazon/carbonado/layout/LayoutProperty.java
index f32cf3f..667e283 100644
--- a/src/main/java/com/amazon/carbonado/layout/LayoutProperty.java
+++ b/src/main/java/com/amazon/carbonado/layout/LayoutProperty.java
@@ -23,6 +23,7 @@ import org.cojen.classfile.TypeDesc;
 import com.amazon.carbonado.FetchException;
 import com.amazon.carbonado.PersistException;
 import com.amazon.carbonado.SupportException;
+import com.amazon.carbonado.UniqueConstraintException;
 
 import com.amazon.carbonado.info.StorableProperty;
 import com.amazon.carbonado.info.StorablePropertyAdapter;
@@ -186,15 +187,22 @@ public class LayoutProperty {
         return mStoredLayoutProperty.toString();
     }
 
-    void store() throws PersistException {
-        if (!mStoredLayoutProperty.tryInsert()) {
-            StoredLayoutProperty existing = mStoredLayoutProperty.copy();
+    void insert() throws PersistException {
+        try {
+            mStoredLayoutProperty.insert();
+        } catch (UniqueConstraintException e) {
+            // If existing record logically matches, update to allow replication.
+            StoredLayoutProperty existing = mStoredLayoutProperty.prepare();
+            mStoredLayoutProperty.copyPrimaryKeyProperties(existing);
             try {
                 existing.load();
-                existing.copyVersionProperty(mStoredLayoutProperty);
-            } catch (FetchException e) {
-                throw e.toPersistException();
+            } catch (FetchException e2) {
+                throw e2.toPersistException();
             }
+            if (!equals(new LayoutProperty(existing))) {
+                throw e;
+            }
+            mStoredLayoutProperty.setVersionNumber(existing.getVersionNumber());
             mStoredLayoutProperty.update();
         }
     }
-- 
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