From 5d3a3fcca7fbc04e60a146e42fb1f65b94e4ea7b Mon Sep 17 00:00:00 2001
From: gtully <gary.tully@gmail.com>
Date: Wed, 17 Oct 2018 12:32:04 +0100
Subject: [PATCH] AMQ-6590 - rework fix to take the recovery hit on clean
 shutdown rather than on restart, trade off availability for short term disk
 usage

---
 .../store/kahadb/disk/page/PageFile.java      | 31 +++++++++++--------
 .../store/kahadb/disk/page/PageFileTest.java  |  4 +--
 2 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/disk/page/PageFile.java b/activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/disk/page/PageFile.java
index 5699c450a2..b426a72311 100644
--- a/activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/disk/page/PageFile.java
+++ b/activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/disk/page/PageFile.java
@@ -145,6 +145,8 @@ public class PageFile {
     private boolean useLFRUEviction = false;
     private float LFUEvictionFactor = 0.2f;
 
+    private boolean needsFreePageRecovery = false;
+
     /**
      * Use to keep track of updated pages which have not yet been committed.
      */
@@ -401,8 +403,6 @@ public class PageFile {
                 recoveryFile = new RecoverableRandomAccessFile(getRecoveryFile(), "rw");
             }
 
-            boolean needsFreePageRecovery = false;
-
             if (metaData.isCleanShutdown()) {
                 nextTxid.set(metaData.getLastTxId() + 1);
                 if (metaData.getFreePages() > 0) {
@@ -419,17 +419,6 @@ public class PageFile {
             }
             nextFreePageId.set((writeFile.length() - PAGE_FILE_HEADER_SIZE) / pageSize);
 
-            if (needsFreePageRecovery) {
-                // Scan all to find the free pages after nextFreePageId is set
-                freeList = new SequenceSet();
-                for (Iterator<Page> i = tx().iterator(true); i.hasNext(); ) {
-                    Page page = i.next();
-                    if (page.getType() == Page.PAGE_FREE_TYPE) {
-                        freeList.add(page.getPageId());
-                    }
-                }
-            }
-
             metaData.setCleanShutdown(false);
             storeMetaData();
             getFreeFile().delete();
@@ -456,6 +445,22 @@ public class PageFile {
                 throw new InterruptedIOException();
             }
 
+            if (needsFreePageRecovery) {
+                LOG.info(toString() + ". Recovering pageFile free list due to prior unclean shutdown..");
+                freeList = new SequenceSet();
+                loaded.set(true);
+                try {
+                    for (Iterator<Page> i = new Transaction(this).iterator(true); i.hasNext(); ) {
+                        Page page = i.next();
+                        if (page.getType() == Page.PAGE_FREE_TYPE) {
+                            freeList.add(page.getPageId());
+                        }
+                    }
+                } finally {
+                    loaded.set(false);
+                }
+            }
+
             if (freeList.isEmpty()) {
                 metaData.setFreePages(0);
             } else {
diff --git a/activemq-kahadb-store/src/test/java/org/apache/activemq/store/kahadb/disk/page/PageFileTest.java b/activemq-kahadb-store/src/test/java/org/apache/activemq/store/kahadb/disk/page/PageFileTest.java
index c5a84e92bf..1bdbe6f379 100644
--- a/activemq-kahadb-store/src/test/java/org/apache/activemq/store/kahadb/disk/page/PageFileTest.java
+++ b/activemq-kahadb-store/src/test/java/org/apache/activemq/store/kahadb/disk/page/PageFileTest.java
@@ -219,10 +219,10 @@ public class PageFileTest extends TestCase {
         PageFile pf2 = new PageFile(new File("target/test-data"), getName());
         pf2.setEnableRecoveryFile(false);
         pf2.load();
-
+        pf2.unload();
+        pf2.load();
         long freePages = pf2.getFreePageCount();
         pf.unload();
-        pf2.unload();
 
         //Make sure that all 10 pages are still tracked
         assertEquals(10, freePages);