1 files changed, 108 insertions, 0 deletions
diff --git a/java/com/google/gerrit/index/IndexCollection.java b/java/com/google/gerrit/index/IndexCollection.java
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+++ b/java/com/google/gerrit/index/IndexCollection.java
@@ -0,0 +1,108 @@
+// Copyright (C) 2013 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.index;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.Lists;
+import com.google.gerrit.extensions.events.LifecycleListener;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.atomic.AtomicReference;
+
+/** Dynamic pointers to the index versions used for searching and writing. */
+public abstract class IndexCollection<K, V, I extends Index<K, V>> implements LifecycleListener {
+  private final CopyOnWriteArrayList<I> writeIndexes;
+  private final AtomicReference<I> searchIndex;
+
+  protected IndexCollection() {
+    this.writeIndexes = Lists.newCopyOnWriteArrayList();
+    this.searchIndex = new AtomicReference<>();
+  }
+
+  /** @return the current search index version. */
+  public I getSearchIndex() {
+    return searchIndex.get();
+  }
+
+  public void setSearchIndex(I index) {
+    setSearchIndex(index, true);
+  }
+
+  @VisibleForTesting
+  public void setSearchIndex(I index, boolean closeOld) {
+    I old = searchIndex.getAndSet(index);
+    if (closeOld && old != null && old != index && !writeIndexes.contains(old)) {
+      old.close();
+    }
+  }
+
+  public Collection<I> getWriteIndexes() {
+    return Collections.unmodifiableCollection(writeIndexes);
+  }
+
+  public synchronized I addWriteIndex(I index) {
+    int version = index.getSchema().getVersion();
+    for (int i = 0; i < writeIndexes.size(); i++) {
+      if (writeIndexes.get(i).getSchema().getVersion() == version) {
+        return writeIndexes.set(i, index);
+      }
+    }
+    writeIndexes.add(index);
+    return null;
+  }
+
+  public synchronized void removeWriteIndex(int version) {
+    int removeIndex = -1;
+    for (int i = 0; i < writeIndexes.size(); i++) {
+      if (writeIndexes.get(i).getSchema().getVersion() == version) {
+        removeIndex = i;
+        break;
+      }
+    }
+    if (removeIndex >= 0) {
+      try {
+        writeIndexes.get(removeIndex).close();
+      } finally {
+        writeIndexes.remove(removeIndex);
+      }
+    }
+  }
+
+  public I getWriteIndex(int version) {
+    for (I i : writeIndexes) {
+      if (i.getSchema().getVersion() == version) {
+        return i;
+      }
+    }
+    return null;
+  }
+
+  @Override
+  public void start() {}
+
+  @Override
+  public void stop() {
+    I read = searchIndex.get();
+    if (read != null) {
+      read.close();
+    }
+    for (I write : writeIndexes) {
+      if (write != read) {
+        write.close();
+      }
+    }
+  }
+}