Merge in the restartable PageCacheWarmer from upstream.

enterprise/kernel/src/main/java/org/neo4j/kernel/impl/pagecache/PageCacheWarmer.java

@@ -69,10 +69,10 @@ public class PageCacheWarmer implements NeoStoreFileListing.StoreFileProvider
     private final FileSystemAbstraction fs;
     private final PageCache pageCache;
     private final JobScheduler scheduler;
-    private volatile boolean stopOngoingWarming;
-    private final ExecutorService executor;
-    private final PageLoaderFactory pageLoaderFactory;
     private final ProfileRefCounts refCounts;
+    private volatile boolean stopOngoingWarming;
+    private ExecutorService executor;
+    private PageLoaderFactory pageLoaderFactory;
 
     PageCacheWarmer( FileSystemAbstraction fs, PageCache pageCache, JobScheduler scheduler )
     {
@@ -104,16 +104,28 @@ public synchronized Resource addFilesTo( Collection<StoreFileMetadata> coll ) th
         };
     }
 
+    public synchronized void start()
+    {
+        stopOngoingWarming = false;
+        executor = buildExecutorService( scheduler );
+        pageLoaderFactory = new PageLoaderFactory( executor, pageCache );
+    }
+
     public void stop()
     {
         stopOngoingWarming = true;
-        synchronized ( this )
+        stopWarmer();
+    }
+
+    /**
+     * Stopping warmer process, needs to be synchronised to prevent racing with profiling and heating
+     */
+    private synchronized void stopWarmer()
+    {
+        if ( executor != null )
         {
-            // This synchronised block means we'll wait for any reheat() or profile() to notice our raised stopped flag,
-            // before we return to the caller. This helps avoid races, e.g. if the page cache is closed while this page
-            // cache warmer is still holding on to some mapped pages.
+            executor.shutdown();
         }
-        executor.shutdown();
     }
 
     /**

enterprise/kernel/src/main/java/org/neo4j/kernel/impl/pagecache/PageCacheWarmerKernelExtension.java

@@ -49,6 +49,7 @@ class PageCacheWarmerKernelExtension extends LifecycleAdapter
     private final Config config;
     private final PageCacheWarmer pageCacheWarmer;
     private volatile JobScheduler.JobHandle profileHandle;
+    private volatile boolean started;
 
     PageCacheWarmerKernelExtension(
             JobScheduler scheduler, AvailabilityGuard availabilityGuard, PageCache pageCache, FileSystemAbstraction fs,
@@ -68,8 +69,10 @@ public void start()
     {
         if ( ENABLED )
         {
+            pageCacheWarmer.start();
             scheduleTryReheat();
             fileListing.get().registerStoreFileProvider( pageCacheWarmer );
+            started = true;
         }
     }
 
@@ -141,11 +144,14 @@ private void doProfile()
     @Override
     public void stop() throws Throwable
     {
-        JobScheduler.JobHandle handle = profileHandle;
-        if ( handle != null )
+        if ( started )
         {
-            handle.cancel( false );
+            JobScheduler.JobHandle handle = profileHandle;
+            if ( handle != null )
+            {
+                handle.cancel( false );
+            }
+            pageCacheWarmer.stop();
         }
-        pageCacheWarmer.stop();
     }
 }

enterprise/kernel/src/test/java/org/neo4j/kernel/impl/pagecache/PageCacheWarmerTest.java

@@ -32,6 +32,7 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.OptionalLong;
 import java.util.concurrent.ThreadLocalRandom;
 
 import org.neo4j.collection.primitive.Primitive;
@@ -57,6 +58,8 @@
 import static org.hamcrest.Matchers.greaterThan;
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 
@@ -102,6 +105,52 @@ private void clearTracerCounts()
         cursorTracer.get().init( cacheTracer );
     }
 
+    @Test
+    public void doNotReheatAfterStop() throws IOException
+    {
+        try ( PageCache pageCache = pageCacheRule.getPageCache( fs, cfg );
+                PagedFile ignore = pageCache.map( file, pageCache.pageSize(), StandardOpenOption.CREATE ) )
+        {
+            PageCacheWarmer warmer = new PageCacheWarmer( fs, pageCache, scheduler );
+            warmer.start();
+            warmer.stop();
+            assertSame( OptionalLong.empty(), warmer.reheat() );
+        }
+    }
+
+    @Test
+    public void doNoProfileAfterStop() throws IOException
+    {
+        try ( PageCache pageCache = pageCacheRule.getPageCache( fs, cfg );
+                PagedFile ignore = pageCache.map( file, pageCache.pageSize(), StandardOpenOption.CREATE ) )
+        {
+            PageCacheWarmer warmer = new PageCacheWarmer( fs, pageCache, scheduler );
+            warmer.start();
+            warmer.stop();
+            assertSame( OptionalLong.empty(), warmer.profile() );
+        }
+    }
+
+    @Test
+    public void profileAndReheatAfterRestart() throws IOException
+    {
+        try ( PageCache pageCache = pageCacheRule.getPageCache( fs, cfg );
+                PagedFile pf = pageCache.map( file, pageCache.pageSize(), StandardOpenOption.CREATE ) )
+        {
+            PageCacheWarmer warmer = new PageCacheWarmer( fs, pageCache, scheduler );
+            warmer.start();
+            warmer.stop();
+            warmer.start();
+            try ( PageCursor writer = pf.io( 0, PagedFile.PF_SHARED_WRITE_LOCK ) )
+            {
+                assertTrue( writer.next( 1 ) );
+                assertTrue( writer.next( 3 ) );
+            }
+            warmer.profile();
+            assertNotSame( OptionalLong.empty(), warmer.reheat() );
+        }
+    }
+
     @Test
     public void mustDoNothingWhenReheatingUnprofiledPageCache() throws Exception
     {
@@ -138,6 +187,7 @@ public void mustReheatProfiledPageCache() throws Exception
               PagedFile pf = pageCache.map( file, pageCache.pageSize() ) )
         {
             PageCacheWarmer warmer = new PageCacheWarmer( fs, pageCache, scheduler );
+            warmer.start();
             warmer.reheat();
 
             pageCache.reportEvents();
@@ -183,6 +233,7 @@ public void reheatingMustWorkOnLargeNumberOfPages() throws Exception
               PagedFile pf = pageCache.map( file, pageCache.pageSize() ) )
         {
             PageCacheWarmer warmer = new PageCacheWarmer( fs, pageCache, scheduler );
+            warmer.start();
             warmer.reheat();
 
             pageCache.reportEvents();
@@ -216,6 +267,7 @@ public void profileMustNotDeleteFilesCurrentlyExposedViaFileListing() throws Exc
             }
             pf.flushAndForce();
             PageCacheWarmer warmer = new PageCacheWarmer( fs, pageCache, scheduler );
+            warmer.start();
             warmer.profile();
             warmer.profile();
             warmer.profile();
@@ -242,6 +294,7 @@ public void profileMustNotDeleteFilesCurrentlyExposedViaFileListing() throws Exc
             }
             // Once we are done with the file listing, profile should remove those files.
             warmer.profile();
+            warmer.stop();
             assertFilesNotExists( fileListing );
         }
     }