HDDS-11668. Recon List Keys API: Reuse key prefix if parentID is the same

hadoop-ozone/recon/src/main/java/org/apache/hadoop/ozone/recon/ReconUtils.java

@@ -317,7 +317,37 @@ public static String constructFullPath(OmKeyInfo omKeyInfo,
   public static String constructFullPath(String keyName, long initialParentId, String volumeName, String bucketName,
                                          ReconNamespaceSummaryManager reconNamespaceSummaryManager,
                                          ReconOMMetadataManager omMetadataManager) throws IOException {
-    StringBuilder fullPath = new StringBuilder(keyName);
+    StringBuilder fullPath = constructFullPathPrefix(initialParentId, volumeName, bucketName,
+        reconNamespaceSummaryManager, omMetadataManager);
+    if (fullPath.length() == 0) {
+      return "";
+    }
+    fullPath.append(keyName);
+    return fullPath.toString();
+  }
+
+
+  /**
+   * Constructs the prefix path to a key from its key name and parent ID using a bottom-up approach, starting from the
+   * leaf node.
+   *
+   * The method begins with the leaf node (the key itself) and recursively prepends parent directory names, fetched
+   * via NSSummary objects, until reaching the parent bucket (parentId is -1). It effectively builds the path from
+   * bottom to top, finally prepending the volume and bucket names to complete the full path. If the directory structure
+   * is currently being rebuilt (indicated by the rebuildTriggered flag), this method returns an empty string to signify
+   * that path construction is temporarily unavailable.
+   *
+   * @param initialParentId The parent ID of the key
+   * @param volumeName The name of the volume
+   * @param bucketName The name of the bucket
+   * @return A StringBuilder containing the constructed prefix path of the key, or an empty string builder if a rebuild
+   *         is in progress.
+   * @throws IOException
+   */
+  public static StringBuilder constructFullPathPrefix(long initialParentId, String volumeName,
+      String bucketName, ReconNamespaceSummaryManager reconNamespaceSummaryManager,
+      ReconOMMetadataManager omMetadataManager) throws IOException {
+    StringBuilder fullPath = new StringBuilder();
     long parentId = initialParentId;
     boolean isDirectoryPresent = false;
 
@@ -326,16 +356,21 @@ public static String constructFullPath(String keyName, long initialParentId, Str
       if (nsSummary == null) {
         log.warn("NSSummary tree is currently being rebuilt or the directory could be in the progress of " +
             "deletion, returning empty string for path construction.");
-        return "";
+        fullPath.setLength(0);
+        return fullPath;
       }
       if (nsSummary.getParentId() == -1) {
         if (rebuildTriggered.compareAndSet(false, true)) {
           triggerRebuild(reconNamespaceSummaryManager, omMetadataManager);
         }
         log.warn("NSSummary tree is currently being rebuilt, returning empty string for path construction.");
-        return "";
+        fullPath.setLength(0);
+        return fullPath;
+      }
+      // On the last pass, dir-name will be empty and parent will be zero, indicating the loop should end.
+      if (!nsSummary.getDirName().isEmpty()) {
+        fullPath.insert(0, nsSummary.getDirName() + OM_KEY_PREFIX);
       }
-      fullPath.insert(0, nsSummary.getDirName() + OM_KEY_PREFIX);
 
       // Move to the parent ID of the current directory
       parentId = nsSummary.getParentId();
@@ -344,10 +379,18 @@ public static String constructFullPath(String keyName, long initialParentId, Str
 
     // Prepend the volume and bucket to the constructed path
     fullPath.insert(0, volumeName + OM_KEY_PREFIX + bucketName + OM_KEY_PREFIX);
+    // TODO - why is this needed? It seems lke it should handle double slashes in the path name,
+    //        but its not clear how they get there. This normalize call is quite expensive as it
+    //        creates several objects (URI, PATH, back to string). There was a bug fixed above
+    //        where the last parent dirName was empty, which always caused a double // after the
+    //        bucket name, but with that fixed, it seems like this should not be needed. All tests
+    //        pass without it for key listing.
     if (isDirectoryPresent) {
-      return OmUtils.normalizeKey(fullPath.toString(), true);
+      String path = fullPath.toString();
+      fullPath.setLength(0);
+      fullPath.append(OmUtils.normalizeKey(path, true));
     }
-    return fullPath.toString();
+    return fullPath;
   }
 
   private static void triggerRebuild(ReconNamespaceSummaryManager reconNamespaceSummaryManager,

hadoop-ozone/recon/src/main/java/org/apache/hadoop/ozone/recon/api/OMDBInsightEndpoint.java

@@ -1176,6 +1176,9 @@ private void retrieveKeysFromTable(
         keyIter.seek(paramInfo.getStartPrefix());
       }
 
+      long prevParentID = -1;
+      StringBuilder keyPrefix = null;
+      int keyPrefixLength = 0;
       while (keyIter.hasNext()) {
         Table.KeyValue<String, KeyEntityInfoProtoWrapper> entry = keyIter.next();
         String dbKey = entry.getKey();
@@ -1189,9 +1192,32 @@ private void retrieveKeysFromTable(
         if (applyFilters(entry, paramInfo)) {
           KeyEntityInfoProtoWrapper keyEntityInfo = entry.getValue();
           keyEntityInfo.setKey(dbKey);
-          keyEntityInfo.setPath(ReconUtils.constructFullPath(keyEntityInfo.getKeyName(), keyEntityInfo.getParentId(),
-              keyEntityInfo.getVolumeName(), keyEntityInfo.getBucketName(), reconNamespaceSummaryManager,
-              omMetadataManager));
+          if (keyEntityInfo.getParentId() == 0) {
+            // Legacy bucket keys have a parentID of zero. OBS bucket keys have a parentID of the bucketID.
+            // FSO keys have a parent of the immediate parent directory.
+            // Legacy buckets are obsolete, so this code path is not optimized. We don't expect to see many Legacy
+            // buckets in practice.
+            prevParentID = -1;
+            keyEntityInfo.setPath(ReconUtils.constructFullPath(keyEntityInfo.getKeyName(), keyEntityInfo.getParentId(),
+                keyEntityInfo.getVolumeName(), keyEntityInfo.getBucketName(), reconNamespaceSummaryManager,
+                omMetadataManager));
+          } else {
+            // As we iterate keys in sorted order, its highly likely that keys have the same prefix for many keys in a
+            // row. Especially for FSO buckets, its expensive to construct the path for each key. So, we construct the
+            // prefix once and reuse it for each identical parent. Only if the parent changes do we need to construct
+            // a new prefix path.
+            if (prevParentID != keyEntityInfo.getParentId()) {
+              prevParentID = keyEntityInfo.getParentId();
+              keyPrefix = ReconUtils.constructFullPathPrefix(keyEntityInfo.getParentId(),
+                  keyEntityInfo.getVolumeName(), keyEntityInfo.getBucketName(), reconNamespaceSummaryManager,
+                  omMetadataManager);
+              keyPrefixLength = keyPrefix.length();
+            }
+            keyPrefix.setLength(keyPrefixLength);
+            keyPrefix.append(keyEntityInfo.getKeyName());
+            keyEntityInfo.setPath(keyPrefix.toString());
+          }
+
           results.add(keyEntityInfo);
           paramInfo.setLastKey(dbKey);
           if (results.size() >= paramInfo.getLimit()) {