[GitHub] [ozone] GeorgeJahad commented on a diff in pull request #3784: HDDS-6854. Implement List Snapshot API

[GitBox <gi...@apache.org>]

GeorgeJahad commented on code in PR #3784:
URL: https://github.com/apache/ozone/pull/3784#discussion_r982739755


##########
hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/OmMetadataManagerImpl.java:
##########
@@ -1125,6 +1125,100 @@ public List<RepeatedOmKeyInfo> listTrash(String volumeName, String bucketName,
     return deletedKeys;
   }
 
+  @Override
+  public List<SnapshotInfo> listSnapshot(String volumeName, String bucketName,
+      String startKey, String prefix) throws IOException {
+    if (Strings.isNullOrEmpty(volumeName)) {
+      throw new OMException("Volume name is required.",
+          ResultCodes.VOLUME_NOT_FOUND);
+    }
+
+    if (Strings.isNullOrEmpty(bucketName)) {
+      throw new OMException("Bucket name is required.",
+          ResultCodes.BUCKET_NOT_FOUND);
+    }
+
+    List<SnapshotInfo> snapshotInfos = new ArrayList<>();
+    TreeMap<String, SnapshotInfo> filteredSnapshotInfoMap = new TreeMap<>();
+    String seekStartKey;
+    boolean skipStartKey = false;
+    if (StringUtil.isNotBlank(startKey)) {
+      // Seek to the specified key.
+      seekStartKey = getOzoneKey(volumeName, bucketName, startKey);
+      skipStartKey = true;
+    } else {
+      // This allows us to seek directly to the first key with the right prefix.
+      seekStartKey = getOzoneKey(volumeName, bucketName,
+          StringUtil.isNotBlank(prefix) ? prefix : OM_KEY_PREFIX);
+    }
+
+    String seekPrefix;
+    if (StringUtil.isNotBlank(prefix)) {
+      seekPrefix = getOzoneKey(volumeName, bucketName, prefix);
+    } else {
+      seekPrefix = getBucketKey(volumeName, bucketName + OM_KEY_PREFIX);
+    }
+
+    filteredSnapshotInfoMap.putAll(
+        getSnapshotFromCache(seekStartKey, seekPrefix));
+    filteredSnapshotInfoMap.putAll(getSnapshotFromDB(seekStartKey, seekPrefix));
+
+    for (Map.Entry<String, SnapshotInfo> cacheKey : filteredSnapshotInfoMap
+        .entrySet()) {
+      if (cacheKey.getKey().equals(seekStartKey) && skipStartKey) {
+        continue;
+      }
+      snapshotInfos.add(cacheKey.getValue());
+    }
+
+    return snapshotInfos;
+  }
+
+  private TreeMap<String, SnapshotInfo> getSnapshotFromCache(
+      String seekStartKey, String seekPrefix) {
+    TreeMap<String, SnapshotInfo> result = new TreeMap<>();
+    Iterator<Map.Entry<CacheKey<String>, CacheValue<SnapshotInfo>>> iterator =
+        snapshotInfoTable.cacheIterator();
+    while (iterator.hasNext()) {
+      Map.Entry<CacheKey<String>, CacheValue<SnapshotInfo>> entry =
+          iterator.next();
+      String snapshotKey = entry.getKey().getCacheKey();
+      SnapshotInfo snapshotInfo = entry.getValue().getCacheValue();
+      if (snapshotInfo != null
+          && snapshotKey.startsWith(seekPrefix)
+          && snapshotKey.compareTo(seekStartKey) >= 0) {
+        result.put(snapshotKey, snapshotInfo);
+      }
+    }
+    return result;
+  }
+
+  private TreeMap<String, SnapshotInfo> getSnapshotFromDB(
+      String seekStartKey, String seekPrefix) throws IOException {
+    TreeMap<String, SnapshotInfo> result = new TreeMap<>();
+    try (TableIterator<String, ? extends KeyValue<String, SnapshotInfo>>
+             snapshotIter = snapshotInfoTable.iterator()) {
+      KeyValue< String, SnapshotInfo> snapshotinfo;
+      snapshotIter.seek(seekStartKey);
+      while (snapshotIter.hasNext()) {
+        snapshotinfo = snapshotIter.next();
+        if (snapshotinfo != null && snapshotinfo.getKey()
+            .startsWith(seekPrefix)) {
+          CacheValue<SnapshotInfo> cacheValue =
+              snapshotInfoTable.getCacheValue(
+                  new CacheKey<>(snapshotinfo.getKey()));
+          if (cacheValue == null || cacheValue.getCacheValue() != null) {

Review Comment:
   I don't understand this:
   ```
    cacheValue.getCacheValue() != null
   ```
   should it be this?:
   ```
    cacheValue.getCacheValue() == null
   ```



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