1 files changed, 168 insertions, 0 deletions
diff --git a/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/utils/ContainerCache.java b/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/utils/ContainerCache.java
new file mode 100644
index 0000000000..6ae45b6d08
--- /dev/null
+++ b/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/utils/ContainerCache.java
@@ -0,0 +1,168 @@
+/*
+ * 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.utils;
+
+import com.google.common.base.Preconditions;
+import org.apache.commons.collections.MapIterator;
+import org.apache.commons.collections.map.LRUMap;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.ozone.OzoneConfigKeys;
+import org.apache.hadoop.utils.MetadataStore;
+import org.apache.hadoop.utils.MetadataStoreBuilder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * container cache is a LRUMap that maintains the DB handles.
+ */
+public final class ContainerCache extends LRUMap {
+  private static final Logger LOG =
+      LoggerFactory.getLogger(ContainerCache.class);
+  private final Lock lock = new ReentrantLock();
+  private static ContainerCache cache;
+  private static final float LOAD_FACTOR = 0.75f;
+  /**
+   * Constructs a cache that holds DBHandle references.
+   */
+  private ContainerCache(int maxSize, float loadFactor, boolean
+      scanUntilRemovable) {
+    super(maxSize, loadFactor, scanUntilRemovable);
+  }
+
+  /**
+   * Return a singleton instance of {@link ContainerCache}
+   * that holds the DB handlers.
+   *
+   * @param conf - Configuration.
+   * @return A instance of {@link ContainerCache}.
+   */
+  public synchronized static ContainerCache getInstance(Configuration conf) {
+    if (cache == null) {
+      int cacheSize = conf.getInt(OzoneConfigKeys.OZONE_CONTAINER_CACHE_SIZE,
+          OzoneConfigKeys.OZONE_CONTAINER_CACHE_DEFAULT);
+      cache = new ContainerCache(cacheSize, LOAD_FACTOR, true);
+    }
+    return cache;
+  }
+
+  /**
+   * Closes a db instance.
+   *
+   * @param container - name of the container to be closed.
+   * @param db - db instance to close.
+   */
+  private void closeDB(String container, MetadataStore db) {
+    if (db != null) {
+      try {
+        db.close();
+      } catch (IOException e) {
+        LOG.error("Error closing DB. Container: " + container, e);
+      }
+    }
+  }
+
+  /**
+   * Closes all the db instances and resets the cache.
+   */
+  public void shutdownCache() {
+    lock.lock();
+    try {
+      // iterate the cache and close each db
+      MapIterator iterator = cache.mapIterator();
+      while (iterator.hasNext()) {
+        iterator.next();
+        MetadataStore db = (MetadataStore) iterator.getValue();
+        closeDB(iterator.getKey().toString(), db);
+      }
+      // reset the cache
+      cache.clear();
+    } finally {
+      lock.unlock();
+    }
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  @Override
+  protected boolean removeLRU(LinkEntry entry) {
+    lock.lock();
+    try {
+      MetadataStore db = (MetadataStore) entry.getValue();
+      closeDB(entry.getKey().toString(), db);
+    } finally {
+      lock.unlock();
+    }
+    return true;
+  }
+
+  /**
+   * Returns a DB handle if available, create the handler otherwise.
+   *
+   * @param containerName - Name of the container.
+   * @return MetadataStore.
+   */
+  public MetadataStore getDB(String containerName, String containerDBPath)
+      throws IOException {
+    Preconditions.checkNotNull(containerName);
+    Preconditions.checkState(!containerName.isEmpty());
+    lock.lock();
+    try {
+      MetadataStore db = (MetadataStore) this.get(containerName);
+
+      if (db == null) {
+        db = MetadataStoreBuilder.newBuilder()
+            .setDbFile(new File(containerDBPath))
+            .setCreateIfMissing(false)
+            .build();
+        this.put(containerName, db);
+      }
+      return db;
+    } catch (Exception e) {
+      LOG.error("Error opening DB. Container:{} ContainerPath:{}",
+          containerName, containerDBPath, e);
+      throw e;
+    } finally {
+      lock.unlock();
+    }
+  }
+
+  /**
+   * Remove a DB handler from cache.
+   *
+   * @param containerName - Name of the container.
+   */
+  public void removeDB(String containerName) {
+    Preconditions.checkNotNull(containerName);
+    Preconditions.checkState(!containerName.isEmpty());
+    lock.lock();
+    try {
+      MetadataStore db = (MetadataStore)this.get(containerName);
+      closeDB(containerName, db);
+      this.remove(containerName);
+    } finally {
+      lock.unlock();
+    }
+  }
+}