Source Code Cross Referenced for SimpleFSLockFactory.java in  » Net » lucene-connector » org » apache » lucene » store » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Net » lucene connector » org.apache.lucene.store 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        package org.apache.lucene.store;
002:
003:        /**
004:         * Licensed to the Apache Software Foundation (ASF) under one or more
005:         * contributor license agreements.  See the NOTICE file distributed with
006:         * this work for additional information regarding copyright ownership.
007:         * The ASF licenses this file to You under the Apache License, Version 2.0
008:         * (the "License"); you may not use this file except in compliance with
009:         * the License.  You may obtain a copy of the License at
010:         *
011:         *     http://www.apache.org/licenses/LICENSE-2.0
012:         *
013:         * Unless required by applicable law or agreed to in writing, software
014:         * distributed under the License is distributed on an "AS IS" BASIS,
015:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016:         * See the License for the specific language governing permissions and
017:         * limitations under the License.
018:         */
019:
020:        import java.io.File;
021:        import java.io.IOException;
022:
023:        /**
024:         * <p>Implements {@link LockFactory} using {@link
025:         * File#createNewFile()}.  This is the default LockFactory
026:         * for {@link FSDirectory}.</p>
027:         *
028:         * <p><b>NOTE:</b> the <a target="_top"
029:         * href="http://java.sun.com/j2se/1.4.2/docs/api/java/io/File.html#createNewFile()">javadocs
030:         * for <code>File.createNewFile</code></a> contain a vague
031:         * yet spooky warning about not using the API for file
032:         * locking.  This warning was added due to <a target="_top"
033:         * href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4676183">this
034:         * bug</a>, and in fact the only known problem with using
035:         * this API for locking is that the Lucene write lock may
036:         * not be released when the JVM exits abnormally.</p>
037:
038:         * <p>When this happens, a {@link LockObtainFailedException}
039:         * is hit when trying to create a writer, in which case you
040:         * need to explicitly clear the lock file first.  You can
041:         * either manually remove the file, or use the {@link
042:         * org.apache.lucene.index.IndexReader#unlock(Directory)}
043:         * API.  But, first be certain that no writer is in fact
044:         * writing to the index otherwise you can easily corrupt
045:         * your index.</p>
046:         *
047:         * <p>If you suspect that this or any other LockFactory is
048:         * not working properly in your environment, you can easily
049:         * test it by using {@link VerifyingLockFactory}, {@link
050:         * LockVerifyServer} and {@link LockStressTest}.</p>
051:         *
052:         * @see LockFactory
053:         */
054:
055:        public class SimpleFSLockFactory extends LockFactory {
056:
057:            /**
058:             * Directory specified by <code>org.apache.lucene.lockDir</code>
059:             * system property.  If that is not set, then <code>java.io.tmpdir</code>
060:             * system property is used.
061:             */
062:
063:            private File lockDir;
064:
065:            /**
066:             * Create a SimpleFSLockFactory instance, with null (unset)
067:             * lock directory.  This is package-private and is only
068:             * used by FSDirectory when creating this LockFactory via
069:             * the System property
070:             * org.apache.lucene.store.FSDirectoryLockFactoryClass.
071:             */
072:            SimpleFSLockFactory() throws IOException {
073:                this ((File) null);
074:            }
075:
076:            /**
077:             * Instantiate using the provided directory (as a File instance).
078:             * @param lockDir where lock files should be created.
079:             */
080:            public SimpleFSLockFactory(File lockDir) throws IOException {
081:                setLockDir(lockDir);
082:            }
083:
084:            /**
085:             * Instantiate using the provided directory name (String).
086:             * @param lockDirName where lock files should be created.
087:             */
088:            public SimpleFSLockFactory(String lockDirName) throws IOException {
089:                lockDir = new File(lockDirName);
090:                setLockDir(lockDir);
091:            }
092:
093:            /**
094:             * Set the lock directory.  This is package-private and is
095:             * only used externally by FSDirectory when creating this
096:             * LockFactory via the System property
097:             * org.apache.lucene.store.FSDirectoryLockFactoryClass.
098:             */
099:            void setLockDir(File lockDir) throws IOException {
100:                this .lockDir = lockDir;
101:            }
102:
103:            public Lock makeLock(String lockName) {
104:                if (lockPrefix != null) {
105:                    lockName = lockPrefix + "-" + lockName;
106:                }
107:                return new SimpleFSLock(lockDir, lockName);
108:            }
109:
110:            public void clearLock(String lockName) throws IOException {
111:                if (lockDir.exists()) {
112:                    if (lockPrefix != null) {
113:                        lockName = lockPrefix + "-" + lockName;
114:                    }
115:                    File lockFile = new File(lockDir, lockName);
116:                    if (lockFile.exists() && !lockFile.delete()) {
117:                        throw new IOException("Cannot delete " + lockFile);
118:                    }
119:                }
120:            }
121:        };
122:
123:        class SimpleFSLock extends Lock {
124:
125:            File lockFile;
126:            File lockDir;
127:
128:            public SimpleFSLock(File lockDir, String lockFileName) {
129:                this .lockDir = lockDir;
130:                lockFile = new File(lockDir, lockFileName);
131:            }
132:
133:            public boolean obtain() throws IOException {
134:
135:                // Ensure that lockDir exists and is a directory:
136:                if (!lockDir.exists()) {
137:                    if (!lockDir.mkdirs())
138:                        throw new IOException("Cannot create directory: "
139:                                + lockDir.getAbsolutePath());
140:                } else if (!lockDir.isDirectory()) {
141:                    throw new IOException(
142:                            "Found regular file where directory expected: "
143:                                    + lockDir.getAbsolutePath());
144:                }
145:                return lockFile.createNewFile();
146:            }
147:
148:            public void release() throws LockReleaseFailedException {
149:                if (lockFile.exists() && !lockFile.delete())
150:                    throw new LockReleaseFailedException("failed to delete "
151:                            + lockFile);
152:            }
153:
154:            public boolean isLocked() {
155:                return lockFile.exists();
156:            }
157:
158:            public String toString() {
159:                return "SimpleFSLock@" + lockFile;
160:            }
161:        }
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