pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / src / java / org / apache / lucene / util / TwoPhaseCommitTool.java

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/util/TwoPhaseCommitTool.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/util/TwoPhaseCommitTool.java
new file mode 100644 (file)
index 0000000..66f3526
--- /dev/null
+++ b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/util/TwoPhaseCommitTool.java
@@ -0,0 +1,162 @@
+package org.apache.lucene.util;
+
+import java.io.IOException;
+import java.util.Map;
+
+/**
+ * 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.
+ */
+
+/**
+ * A utility for executing 2-phase commit on several objects.
+ * 
+ * @see TwoPhaseCommit
+ * @lucene.experimental
+ */
+public final class TwoPhaseCommitTool {
+
+  /**
+   * A wrapper of a {@link TwoPhaseCommit}, which delegates all calls to the
+   * wrapped object, passing the specified commitData. This object is useful for
+   * use with {@link TwoPhaseCommitTool#execute(TwoPhaseCommit...)} if one would
+   * like to store commitData as part of the commit.
+   */
+  public static final class TwoPhaseCommitWrapper implements TwoPhaseCommit {
+
+    private final TwoPhaseCommit tpc;
+    private  final Map<String, String> commitData;
+
+    public TwoPhaseCommitWrapper(TwoPhaseCommit tpc, Map<String, String> commitData) {
+      this.tpc = tpc;
+      this.commitData = commitData;
+    }
+
+    public void prepareCommit() throws IOException {
+      prepareCommit(commitData);
+    }
+
+    public void prepareCommit(Map<String, String> commitData) throws IOException {
+      tpc.prepareCommit(this.commitData);
+    }
+
+    public void commit() throws IOException {
+      commit(commitData);
+    }
+
+    public void commit(Map<String, String> commitData) throws IOException {
+      tpc.commit(this.commitData);
+    }
+
+    public void rollback() throws IOException {
+      tpc.rollback();
+    }
+  }
+  
+  /**
+   * Thrown by {@link TwoPhaseCommitTool#execute(TwoPhaseCommit...)} when an
+   * object fails to prepareCommit().
+   */
+  public static class PrepareCommitFailException extends IOException {
+    
+    public PrepareCommitFailException(Throwable cause, TwoPhaseCommit obj) {
+      super("prepareCommit() failed on " + obj);
+      initCause(cause);
+    }
+    
+  }
+
+  /**
+   * Thrown by {@link TwoPhaseCommitTool#execute(TwoPhaseCommit...)} when an
+   * object fails to commit().
+   */
+  public static class CommitFailException extends IOException {
+    
+    public CommitFailException(Throwable cause, TwoPhaseCommit obj) {
+      super("commit() failed on " + obj);
+      initCause(cause);
+    }
+    
+  }
+
+  /** rollback all objects, discarding any exceptions that occur. */
+  private static void rollback(TwoPhaseCommit... objects) {
+    for (TwoPhaseCommit tpc : objects) {
+      // ignore any exception that occurs during rollback - we want to ensure
+      // all objects are rolled-back.
+      if (tpc != null) {
+        try {
+          tpc.rollback();
+        } catch (Throwable t) {}
+      }
+    }
+  }
+
+  /**
+   * Executes a 2-phase commit algorithm by first
+   * {@link TwoPhaseCommit#prepareCommit()} all objects and only if all succeed,
+   * it proceeds with {@link TwoPhaseCommit#commit()}. If any of the objects
+   * fail on either the preparation or actual commit, it terminates and
+   * {@link TwoPhaseCommit#rollback()} all of them.
+   * <p>
+   * <b>NOTE:</b> it may happen that an object fails to commit, after few have
+   * already successfully committed. This tool will still issue a rollback
+   * instruction on them as well, but depending on the implementation, it may
+   * not have any effect.
+   * <p>
+   * <b>NOTE:</b> if any of the objects are {@code null}, this method simply
+   * skips over them.
+   * 
+   * @throws PrepareCommitFailException
+   *           if any of the objects fail to
+   *           {@link TwoPhaseCommit#prepareCommit()}
+   * @throws CommitFailException
+   *           if any of the objects fail to {@link TwoPhaseCommit#commit()}
+   */
+  public static void execute(TwoPhaseCommit... objects)
+      throws PrepareCommitFailException, CommitFailException {
+    TwoPhaseCommit tpc = null;
+    try {
+      // first, all should successfully prepareCommit()
+      for (int i = 0; i < objects.length; i++) {
+        tpc = objects[i];
+        if (tpc != null) {
+          tpc.prepareCommit();
+        }
+      }
+    } catch (Throwable t) {
+      // first object that fails results in rollback all of them and
+      // throwing an exception.
+      rollback(objects);
+      throw new PrepareCommitFailException(t, tpc);
+    }
+    
+    // If all successfully prepareCommit(), attempt the actual commit()
+    try {
+      for (int i = 0; i < objects.length; i++) {
+        tpc = objects[i];
+        if (tpc != null) {
+          tpc.commit();
+        }
+      }
+    } catch (Throwable t) {
+      // first object that fails results in rollback all of them and
+      // throwing an exception.
+      rollback(objects);
+      throw new CommitFailException(t, tpc);
+    }
+  }
+
+}