[tomcat] 03/05: Fix https://bz.apache.org/bugzilla/show_bug.cgi?id=62841 BackupManager

[ma...@apache.org]

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markt pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/tomcat.git

commit bcf1b79959febb21dbc947d06873251f3a02d758
Author: Mark Thomas <ma...@apache.org>
AuthorDate: Tue May 21 22:35:16 2019 +0100

    Fix https://bz.apache.org/bugzilla/show_bug.cgi?id=62841 BackupManager
    
    Expand the fix to the BackupManager by refactoring the locking into the
    DeltaSession and ensuring that the session is not locked during
    serialization.
---
 .../apache/catalina/ha/session/DeltaSession.java   | 51 +++++++++++++++++-----
 1 file changed, 41 insertions(+), 10 deletions(-)

diff --git a/java/org/apache/catalina/ha/session/DeltaSession.java b/java/org/apache/catalina/ha/session/DeltaSession.java
index 07b4cca..d9afe90 100644
--- a/java/org/apache/catalina/ha/session/DeltaSession.java
+++ b/java/org/apache/catalina/ha/session/DeltaSession.java
@@ -138,12 +138,29 @@ public class DeltaSession extends StandardSession implements Externalizable,Clus
      */
     @Override
     public byte[] getDiff() throws IOException {
-        lockInternal();
-        try {
-            return getDeltaRequest().serialize();
-        } finally{
-            unlockInternal();
+        SynchronizedStack<DeltaRequest> deltaRequestPool = null;
+        DeltaRequest newDeltaRequest = null;
+
+        if (manager instanceof ClusterManagerBase) {
+            deltaRequestPool = ((ClusterManagerBase) manager).getDeltaRequestPool();
+            newDeltaRequest = deltaRequestPool.pop();
         }
+        if (newDeltaRequest == null) {
+            newDeltaRequest = new DeltaRequest();
+        }
+
+        DeltaRequest oldDeltaRequest = replaceDeltaRequest(newDeltaRequest);
+
+        byte[] result = oldDeltaRequest.serialize();
+
+        if (deltaRequestPool != null) {
+            // Only need to reset the old request if it is going to be pooled.
+            // Otherwise let GC do its thing.
+            oldDeltaRequest.reset();
+            deltaRequestPool.push(oldDeltaRequest);
+        }
+
+        return result;
     }
 
     public ClassLoader[] getClassLoaders() {
@@ -183,32 +200,46 @@ public class DeltaSession extends StandardSession implements Externalizable,Clus
     }
 
     /**
-     * Resets the current diff state and resets the dirty flag
+     * {@inheritDoc}
+     * <p>
+     * This implementation is a NO-OP. The diff is reset in {@link #getDiff()}.
      */
     @Override
     public void resetDiff() {
         resetDeltaRequest();
     }
 
+    /**
+     * {@inheritDoc}
+     * <p>
+     * This implementation is a NO-OP. Any required locking takes place in the
+     * methods that make modifications.
+     */
     @Override
     public void lock() {
-        lockInternal();
+        // NO-OP
     }
 
+    /**
+     * {@inheritDoc}
+     * <p>
+     * This implementation is a NO-OP. Any required unlocking takes place in the
+     * methods that make modifications.
+     */
     @Override
     public void unlock() {
-        unlockInternal();
+        // NO-OP
     }
 
     /**
-     * Lock during serialization
+     * Lock during serialization.
      */
     private void lockInternal() {
         diffLock.lock();
     }
 
     /**
-     * Unlock after serialization
+     * Unlock after serialization.
      */
     private void unlockInternal() {
         diffLock.unlock();


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