1 files changed, 91 insertions, 0 deletions
diff --git a/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/impl/TopNOrderedContainerDeletionChoosingPolicy.java b/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/impl/TopNOrderedContainerDeletionChoosingPolicy.java
new file mode 100644
index 0000000000..0169a96cf9
--- /dev/null
+++ b/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/impl/TopNOrderedContainerDeletionChoosingPolicy.java
@@ -0,0 +1,91 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.apache.hadoop.ozone.container.common.impl;
+
+import com.google.common.base.Preconditions;
+import org.apache.hadoop.hdds.scm.container.common.helpers
+    .StorageContainerException;
+import org.apache.hadoop.ozone.container.common.helpers.ContainerData;
+import org.apache.hadoop.ozone.container.common.interfaces
+    .ContainerDeletionChoosingPolicy;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * TopN Ordered choosing policy that choosing containers based on pending
+ * deletion blocks' number.
+ */
+public class TopNOrderedContainerDeletionChoosingPolicy
+    implements ContainerDeletionChoosingPolicy {
+  private static final Logger LOG =
+      LoggerFactory.getLogger(TopNOrderedContainerDeletionChoosingPolicy.class);
+
+  /** customized comparator used to compare differentiate container status. **/
+  private static final Comparator<ContainerStatus> CONTAINER_STATUS_COMPARATOR
+      = new Comparator<ContainerStatus>() {
+        @Override
+        public int compare(ContainerStatus c1, ContainerStatus c2) {
+          return Integer.compare(c2.getNumPendingDeletionBlocks(),
+              c1.getNumPendingDeletionBlocks());
+        }
+      };
+
+  @Override
+  public List<ContainerData> chooseContainerForBlockDeletion(int count,
+      Map<String, ContainerStatus> candidateContainers)
+      throws StorageContainerException {
+    Preconditions.checkNotNull(candidateContainers,
+        "Internal assertion: candidate containers cannot be null");
+
+    List<ContainerData> result = new LinkedList<>();
+    List<ContainerStatus> orderedList = new LinkedList<>();
+    orderedList.addAll(candidateContainers.values());
+    Collections.sort(orderedList, CONTAINER_STATUS_COMPARATOR);
+
+    // get top N list ordered by pending deletion blocks' number
+    int currentCount = 0;
+    for (ContainerStatus entry : orderedList) {
+      if (currentCount < count) {
+        if (entry.getNumPendingDeletionBlocks() > 0) {
+          result.add(entry.getContainer());
+          currentCount++;
+
+          LOG.debug(
+              "Select container {} for block deletion, "
+                  + "pending deletion blocks num: {}.",
+              entry.getContainer().getContainerName(),
+              entry.getNumPendingDeletionBlocks());
+        } else {
+          LOG.debug("Stop looking for next container, there is no"
+              + " pending deletion block contained in remaining containers.");
+          break;
+        }
+      } else {
+        break;
+      }
+    }
+
+    return result;
+  }
+}