From 47db4714fce537a259aa0ea1e43b482b57557bd5 Mon Sep 17 00:00:00 2001
From: Francesco Nigro <nigro.fra@gmail.com>
Date: Sun, 6 Jan 2019 11:48:14 +0100
Subject: [PATCH] ARTEMIS-2216 Avoid unnecessary page cache queries on ack TX

PageSubscriptionImpl::ackTx is already performing a counter update
using the message persistent size: the size can be reused on
PagePosition::setPersistentSize, avoiding to query the page cache just
to compute it.
---
 .../cursor/impl/PageSubscriptionImpl.java     | 32 ++++++++++++++++---
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/artemis-server/src/main/java/org/apache/activemq/artemis/core/paging/cursor/impl/PageSubscriptionImpl.java b/artemis-server/src/main/java/org/apache/activemq/artemis/core/paging/cursor/impl/PageSubscriptionImpl.java
index d7ab42faf4..af29422667 100644
--- a/artemis-server/src/main/java/org/apache/activemq/artemis/core/paging/cursor/impl/PageSubscriptionImpl.java
+++ b/artemis-server/src/main/java/org/apache/activemq/artemis/core/paging/cursor/impl/PageSubscriptionImpl.java
@@ -461,11 +461,22 @@ public final class PageSubscriptionImpl implements PageSubscription {
 
    }
 
+   private void confirmPosition(final Transaction tx, final PagePosition position, final long persistentSize) throws Exception {
+      // if the cursor is persistent
+      if (persistent) {
+         store.storeCursorAcknowledgeTransactional(tx.getID(), cursorId, position);
+      }
+      installTXCallback(tx, position, persistentSize);
+   }
+
    @Override
    public void ackTx(final Transaction tx, final PagedReference reference) throws Exception {
-      confirmPosition(tx, reference.getPosition());
+      //pre-calculate persistentSize
+      final long persistentSize = getPersistentSize(reference);
 
-      counter.increment(tx, -1, -getPersistentSize(reference));
+      confirmPosition(tx, reference.getPosition(), persistentSize);
+
+      counter.increment(tx, -1, -persistentSize);
 
       PageTransactionInfo txInfo = getPageTransaction(reference);
       if (txInfo != null) {
@@ -864,11 +875,16 @@ public final class PageSubscriptionImpl implements PageSubscription {
       return info;
    }
 
+   private void installTXCallback(final Transaction tx, final PagePosition position) {
+      installTXCallback(tx, position, -1);
+   }
+
    /**
     * @param tx
     * @param position
+    * @param persistentSize if negative it needs to be calculated on the fly
     */
-   private void installTXCallback(final Transaction tx, final PagePosition position) {
+   private void installTXCallback(final Transaction tx, final PagePosition position, final long persistentSize) {
       if (position.getRecordID() >= 0) {
          // It needs to persist, otherwise the cursor will return to the fist page position
          tx.setContainsPersistent();
@@ -876,9 +892,15 @@ public final class PageSubscriptionImpl implements PageSubscription {
 
       PageCursorInfo info = getPageInfo(position);
       PageCache cache = info.getCache();
-      long size = 0;
       if (cache != null) {
-         size = getPersistentSize(cache.getMessage(position.getMessageNr()));
+         final long size;
+         if (persistentSize < 0) {
+            //cache.getMessage is potentially expensive depending
+            //on the current cache size and which message is queried
+            size = getPersistentSize(cache.getMessage(position.getMessageNr()));
+         } else {
+            size = persistentSize;
+         }
          position.setPersistentSize(size);
       }