1 /*
2 * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package com.sun.tools.sjavac.server;
27
28 import java.io.File;
29 import java.io.FileNotFoundException;
30 import java.io.IOException;
31 import java.io.RandomAccessFile;
32 import java.nio.channels.ClosedChannelException;
33 import java.nio.channels.FileChannel;
34 import java.nio.channels.FileLock;
35 import java.nio.channels.FileLockInterruptionException;
36 import java.util.concurrent.Semaphore;
37
38 import com.sun.tools.javac.util.Assert;
39 import com.sun.tools.sjavac.Log;
40 import com.sun.tools.sjavac.client.PortFileInaccessibleException;
41
42 /**
43 * The PortFile class mediates access to a short binary file containing the tcp/ip port (for the localhost)
44 * and a cookie necessary for the server answering on that port. The file can be locked using file system
45 * primitives to avoid race conditions when several javac clients are started at the same. Note that file
46 * system locking is not always supported on a all operating systems and/or file systems.
47 *
48 * <p><b>This is NOT part of any supported API.
49 * If you write code that depends on this, you do so at your own risk.
50 * This code and its internal interfaces are subject to change or
51 * deletion without notice.</b>
52 */
53 public class PortFile {
54
55 // Port file format:
56 // byte ordering: high byte first = big endian
57 // Magic nr, 4 byte int, first in file.
58 private final static int magicNr = 0x1174;
59 // Followed by a 4 byte int, with the port nr.
60 // Followed by a 8 byte long, with cookie nr.
61
62 private String filename;
63 private File file;
64 private File stopFile;
65 private RandomAccessFile rwfile;
66 private FileChannel channel;
67
68 // FileLock used to solve inter JVM synchronization, lockSem used to avoid
69 // JVM internal OverlappingFileLockExceptions.
70 // Class invariant: lock.isValid() <-> lockSem.availablePermits() == 0
71 private FileLock lock;
72 private Semaphore lockSem = new Semaphore(1);
73
74 private boolean containsPortInfo;
75 private int serverPort;
76 private long serverCookie;
77 private int myServerPort;
78 private long myServerCookie;
79
80 /**
81 * Create a new portfile.
82 * @param fn is the path to the file.
83 */
84 public PortFile(String fn) {
85 filename = fn;
86 file = new File(filename);
87 stopFile = new File(filename+".stop");
88 containsPortInfo = false;
89 lock = null;
90 }
91
92 private void initializeChannel() throws PortFileInaccessibleException {
93 try {
94 rwfile = new RandomAccessFile(file, "rw");
95 } catch (FileNotFoundException e) {
96 // Reached if file for instance already exists and is a directory
97 throw new PortFileInaccessibleException(e);
98 }
99 // The rwfile should only be readable by the owner of the process
100 // and no other! How do we do that on a RandomAccessFile?
101 channel = rwfile.getChannel();
102 }
103
104 /**
105 * Lock the port file.
106 */
107 public void lock() throws IOException, InterruptedException {
108 if (channel == null) {
109 initializeChannel();
110 }
111 lockSem.acquire();
112 lock = channel.lock();
113 }
114
115 /**
116 * Read the values from the port file in the file system.
117 * Expects the port file to be locked.
118 */
119 public void getValues() {
120 containsPortInfo = false;
121 if (lock == null) {
122 // Not locked, remain ignorant about port file contents.
123 return;
124 }
125 try {
126 if (rwfile.length()>0) {
127 rwfile.seek(0);
128 int nr = rwfile.readInt();
129 serverPort = rwfile.readInt();
130 serverCookie = rwfile.readLong();
131
132 if (nr == magicNr) {
133 containsPortInfo = true;
134 } else {
135 containsPortInfo = false;
136 }
137 }
138 } catch (IOException e) {
139 containsPortInfo = false;
140 }
141 }
142
143 /**
144 * Did the locking and getValues succeed?
145 */
146 public boolean containsPortInfo() {
147 return containsPortInfo;
148 }
149
150 /**
151 * If so, then we can acquire the tcp/ip port on localhost.
152 */
153 public int getPort() {
154 Assert.check(containsPortInfo);
155 return serverPort;
156 }
157
158 /**
159 * If so, then we can acquire the server cookie.
160 */
161 public long getCookie() {
162 Assert.check(containsPortInfo);
163 return serverCookie;
164 }
165
166 /**
167 * Store the values into the locked port file.
168 */
169 public void setValues(int port, long cookie) throws IOException {
170 Assert.check(lock != null);
171 rwfile.seek(0);
172 // Write the magic nr that identifies a port file.
173 rwfile.writeInt(magicNr);
174 rwfile.writeInt(port);
175 rwfile.writeLong(cookie);
176 myServerPort = port;
177 myServerCookie = cookie;
178 }
179
180 /**
181 * Delete the port file.
182 */
183 public void delete() throws IOException, InterruptedException {
184 // Access to file must be closed before deleting.
185 rwfile.close();
186
187 file.delete();
188
189 // Wait until file has been deleted (deletes are asynchronous on Windows!) otherwise we
190 // might shutdown the server and prevent another one from starting.
191 for (int i = 0; i < 10 && file.exists(); i++) {
192 Thread.sleep(1000);
193 }
194 if (file.exists()) {
195 throw new IOException("Failed to delete file.");
196 }
197 }
198
199 /**
200 * Is the port file still there?
201 */
202 public boolean exists() throws IOException {
203 return file.exists();
204 }
205
206 /**
207 * Is a stop file there?
208 */
209 public boolean markedForStop() throws IOException {
210 if (stopFile.exists()) {
211 try {
212 stopFile.delete();
213 } catch (Exception e) {
214 }
215 return true;
216 }
217 return false;
218 }
219
220 /**
221 * Unlock the port file.
222 */
223 public void unlock() throws IOException {
224 if (lock == null) {
225 return;
226 }
227 lock.release();
228 lock = null;
229 lockSem.release();
230 }
231
232 /**
233 * Wait for the port file to contain values that look valid.
234 */
235 public void waitForValidValues() throws IOException, InterruptedException {
236 final int MS_BETWEEN_ATTEMPTS = 500;
237 long startTime = System.currentTimeMillis();
238 long timeout = startTime + getServerStartupTimeoutSeconds() * 1000;
239 while (true) {
240 Log.debug("Looking for valid port file values...");
241 if (exists()) {
242 lock();
243 getValues();
244 unlock();
245 }
246 if (containsPortInfo) {
247 Log.debug("Valid port file values found after " + (System.currentTimeMillis() - startTime) + " ms");
248 return;
249 }
250 if (System.currentTimeMillis() > timeout) {
251 break;
252 }
253 Thread.sleep(MS_BETWEEN_ATTEMPTS);
254 }
255 throw new IOException("No port file values materialized. Giving up after " +
256 (System.currentTimeMillis() - startTime) + " ms");
257 }
258
259 /**
260 * Check if the portfile still contains my values, assuming that I am the server.
261 */
262 public boolean stillMyValues() throws IOException, FileNotFoundException, InterruptedException {
263 for (;;) {
264 try {
265 lock();
266 getValues();
267 unlock();
268 if (containsPortInfo) {
269 if (serverPort == myServerPort &&
270 serverCookie == myServerCookie) {
271 // Everything is ok.
272 return true;
273 }
274 // Someone has overwritten the port file.
275 // Probably another javac server, lets quit.
276 return false;
277 }
278 // Something else is wrong with the portfile. Lets quit.
279 return false;
280 } catch (FileLockInterruptionException e) {
281 continue;
282 }
283 catch (ClosedChannelException e) {
284 // The channel has been closed since sjavac is exiting.
285 return false;
286 }
287 }
288 }
289
290 /**
291 * Return the name of the port file.
292 */
293 public String getFilename() {
294 return filename;
295 }
296
297 private long getServerStartupTimeoutSeconds() {
298 String str = System.getProperty("serverStartupTimeout");
299 if (str != null) {
300 try {
301 return Integer.parseInt(str);
302 } catch (NumberFormatException e) {
303 }
304 }
305 return 60;
306 }
307 }