hasHitory() should check history cache first

fixes #4064

Author: vladak

opengrok-indexer/src/main/java/org/opengrok/indexer/history/AnnotationCache.java

@@ -37,6 +37,7 @@ public interface AnnotationCache extends Cache {
      * @param file file under source root to get the annotation for
      * @param rev requested revision
      * @return {@link Annotation} object or <code>null</code>
+     * @throws AnnotationException on error
      */
     @Nullable
     Annotation get(File file, String rev) throws AnnotationException;

opengrok-indexer/src/main/java/org/opengrok/indexer/history/Cache.java

@@ -23,6 +23,7 @@
 package org.opengrok.indexer.history;
 
 import org.opengrok.indexer.logger.LoggerFactory;
+import org.opengrok.indexer.util.ForbiddenSymlinkException;
 
 import java.io.File;
 import java.util.Collection;
@@ -91,4 +92,13 @@ public interface Cache {
      * @return {@code true} if the file is in the cache, {@code false} otherwise
      */
     boolean hasCacheForFile(File file) throws HistoryException;
+
+    /**
+     * @param file source file
+     * @return whether cache entry for given file is fresh
+     * @throws HistoryException on error
+     * @throws ForbiddenSymlinkException on error
+     * TODO: HistoryException -> CacheException
+     */
+    boolean isUpToDate(File file) throws HistoryException, ForbiddenSymlinkException;
 }

opengrok-indexer/src/main/java/org/opengrok/indexer/history/FileAnnotationCache.java

@@ -97,6 +97,20 @@ Annotation readAnnotation(File file) throws AnnotationException {
         }
     }
 
+    /**
+     * This is potentially expensive operation as the cache entry has to be retrieved from disk
+     * in order to tell whether it is stale or not.
+     * @param file source file
+     * @return indication whether the cache entry is fresh
+     */
+    public boolean isUpToDate(File file) {
+        try {
+            return get(file, null) != null;
+        } catch (AnnotationException e) {
+            return false;
+        }
+    }
+
     public Annotation get(File file, @Nullable String rev) throws AnnotationException {
         Annotation annotation = null;
         String latestRevision = LatestRevisionUtil.getLatestRevision(file);

opengrok-indexer/src/main/java/org/opengrok/indexer/history/FileHistoryCache.java

@@ -595,8 +595,8 @@ private void createDirectoriesForFiles(Set<String> files, Repository repository,
     public History get(File file, Repository repository, boolean withFiles)
             throws HistoryException, ForbiddenSymlinkException {
 
-        File cacheFile = getCachedFile(file);
-        if (isUpToDate(file, cacheFile)) {
+        if (isUpToDate(file)) {
+            File cacheFile = getCachedFile(file);
             try {
                 if (fileHistoryCacheHits != null) {
                     fileHistoryCacheHits.increment();
@@ -616,10 +616,10 @@ public History get(File file, Repository repository, boolean withFiles)
 
     /**
      * @param file the file to check
-     * @param cachedFile the file which contains the cached history for the file
      * @return {@code true} if the cache is up-to-date for the file, {@code false} otherwise
      */
-    private boolean isUpToDate(File file, File cachedFile) {
+    public boolean isUpToDate(File file) throws HistoryException, ForbiddenSymlinkException {
+        File cachedFile = getCachedFile(file);
         return cachedFile != null && cachedFile.exists() && file.lastModified() <= cachedFile.lastModified();
     }
 

opengrok-indexer/src/main/java/org/opengrok/indexer/history/HistoryGuru.java

@@ -584,12 +584,22 @@ public InputStream getRevision(String parent, String basename, String rev) {
     }
 
     /**
-     * Does this directory contain files with source control information ?
-     *
      * @param file File object
-     * @return true if the files in this directory have associated revision history
+     * @return whether it is possible to retrieve history for the file in any way
      */
     public boolean hasHistory(File file) {
+        // If there is a cache entry that is fresh, there is no need to check the repository,
+        // as the cache entry will be preferred in getHistory(), barring any time sensitive issues (TOUTOC).
+        if (hasHistoryCacheForFile(file)) {
+            try {
+                if (historyCache.isUpToDate(file)) {
+                    return true;
+                }
+            } catch (HistoryException | ForbiddenSymlinkException e) {
+                LOGGER.log(Level.FINEST, "cannot determine if history cache for ''{0}'' is fresh", file);
+            }
+        }
+
         Repository repo = getRepository(file);
         if (repo == null) {
             LOGGER.log(Level.FINEST, "cannot find repository for ''{0}}'' to check history presence", file);