ALF-9613: fix some cases of content being in in-memory cache but not on disk.

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@29957 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/content/caching/CachingContentStore.java

@@ -49,7 +49,8 @@ public class CachingContentStore implements ContentStore
     private ContentCache cache;
     private boolean cacheOnInbound;
     
-    static {
+    static
+    {
         locks = new Object[numLocks];
         for (int i = 0; i < numLocks; i++)
         {
@@ -152,22 +153,42 @@ public class CachingContentStore implements ContentStore
         // when it should only be read once and cached versions should be returned after that.
         synchronized(lock(contentUrl))
         {
-            if (!cache.contains(contentUrl))
+            return retryingCacheRead(contentUrl);
+        }
+    }    
+    
+    private ContentReader retryingCacheRead(String url)
+    {
+        int triesLeft = 15;
+        
+        while (triesLeft > 0)
+        {
+            try
             {
-                ContentReader bsReader = backingStore.getReader(contentUrl);
+                return cache.getReader(url);
-                if (!cache.put(contentUrl, bsReader))
+            }
+            catch (CacheMissException e)
+            {
+                // Cached content is missing either from memory or disk
+                // so try and populate it and retry reading it.
+                ContentReader bsReader = backingStore.getReader(url);
+                if (!cache.put(url, bsReader))
                 {
-                    // Content wasn't put into cache successfully.
+                    // Content was empty - probably hasn't been written yet.
                     return bsReader.getReader();
                 }
-            }           
+                else
+                {
+                    triesLeft--;
+                }
+            }
         }
- 
+        
-        // TODO: what if, in the meantime this item has been deleted from the disk cache?
+        // Give up and use the backing store directly
-        return cache.getReader(contentUrl);
+        return backingStore.getReader(url);
     }
-
+    
-
+    
     /*
      * @see org.alfresco.repo.content.ContentStore#getWriter(org.alfresco.repo.content.ContentContext)
      */

source/java/org/alfresco/repo/content/caching/CachingContentStoreSpringTest.java

@@ -19,6 +19,7 @@
 package org.alfresco.repo.content.caching;
 
 import java.io.File;
+import java.io.FilenameFilter;
 
 import net.sf.ehcache.CacheManager;
 
@@ -137,6 +138,30 @@ public class CachingContentStoreSpringTest extends AbstractWritableContentStoreT
     }
     
     
+    public void testStoreWillRecoverFromDeletedCacheFile()
+    {
+        final String content = "Content for " + getName() + " test.";
+        
+        // Write some content to the backing store.
+        ContentWriter writer = backingStore.getWriter(ContentContext.NULL_CONTEXT);
+        writer.putContent(content);
+        final String contentUrl = writer.getContentUrl();
+        
+        // Read content using the CachingContentStore - will cause content to be cached.
+        String retrievedContent = store.getReader(contentUrl).getContentString();
+        assertEquals(content, retrievedContent);
+        
+        // Remove the cached disk file
+        File cacheFile = new File(cache.cacheFileLocation(contentUrl));
+        cacheFile.delete();   
+        assertTrue("Cached content should have been deleted", !cacheFile.exists());
+      
+        // Should still be able to ask for this content, even though the cache file was
+        // deleted and the record of the cache is still in the in-memory cache/lookup.
+        String contentAfterDelete = store.getReader(contentUrl).getContentString();
+        assertEquals(content, contentAfterDelete);
+    }
+    
     
     /*
      * @see org.alfresco.repo.content.AbstractReadOnlyContentStoreTest#getStore()

source/java/org/alfresco/repo/content/caching/CachingContentStoreTest.java

@@ -75,7 +75,6 @@ public class CachingContentStoreTest
     public void getReaderForItemInCache()
     {
         ContentReader cachedContentReader = mock(ContentReader.class);
-        when(cache.contains("url")).thenReturn(true);
         when(cache.getReader("url")).thenReturn(cachedContentReader);
         
         ContentReader returnedReader = cachingStore.getReader("url");
@@ -86,16 +85,25 @@ public class CachingContentStoreTest
     
     
     @Test
-    public void getReadForItemMissingFromCache()
+    public void getReaderForItemMissingFromCache()
     {
         ContentReader sourceContent = mock(ContentReader.class);
-        when(cache.contains("url")).thenReturn(false);
+        when(cache.getReader("url")).thenThrow(new CacheMissException("url"));
         when(backingStore.getReader("url")).thenReturn(sourceContent);
+        when(cache.put("url", sourceContent)).thenReturn(true);
         
         cachingStore.getReader("url");
+    }
+    
+    @Test
+    public void getReaderForItemMissingFromCacheButNoContentToCache()
+    {
+        ContentReader sourceContent = mock(ContentReader.class);
+        when(cache.getReader("url")).thenThrow(new CacheMissException("url"));
+        when(backingStore.getReader("url")).thenReturn(sourceContent);
+        when(cache.put("url", sourceContent)).thenReturn(false);
         
-        verify(backingStore).getReader("url");
+        cachingStore.getReader("url");
-        verify(cache).put("url", sourceContent);
     }
     
     

source/java/org/alfresco/repo/content/caching/ContentCacheImpl.java

@@ -63,7 +63,11 @@ public class ContentCacheImpl implements ContentCache
         if (memoryStore.contains(contentUrl))
         {
             String path = memoryStore.get(contentUrl);
-            return new FileContentReader(new File(path), contentUrl);
+            File cacheFile = new File(path);
+            if (cacheFile.exists())
+            {
+                return new FileContentReader(cacheFile, contentUrl);
+            }
         }
         
         throw new CacheMissException(contentUrl);
@@ -173,4 +177,13 @@ public class ContentCacheImpl implements ContentCache
     {
         this.memoryStore = memoryStore;
     }
+    
+    
+    // Not part of the ContentCache interface as this breaks encapsulation.
+    // Handy method for tests though, since it allows us to find out where
+    // the content was cached.
+    protected String cacheFileLocation(String url)
+    {
+        return memoryStore.get(url);
+    }
 }