1 /*

     2  * Copyright (c) 2019, 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 jdk.dns.client.internal.util;

    27 

    28 import java.io.IOException;

    29 import java.nio.file.Files;

    30 import java.nio.file.Path;

    31 import java.security.AccessController;

    32 import java.security.PrivilegedAction;

    33 import java.security.PrivilegedActionException;

    34 import java.security.PrivilegedExceptionAction;

    35 import java.util.concurrent.atomic.AtomicLong;

    36 

    37 public class ReloadTracker {

    38 

    39     public static ReloadTracker newInstance(Path fileToTrack, long refreshTimeoutMillis) {

    40         Path absolutePath = fileToTrack.toAbsolutePath();

    41         return new ReloadTracker(absolutePath, refreshTimeoutMillis);

    42     }

    43 

    44     public static class ReloadStatus {

    45         private final boolean isReloadNeeded;

    46         private final long lastModificationTimestamp;

    47         private final boolean fileExists;

    48 

    49         ReloadStatus(boolean fileExists, boolean isReloadNeeded, long lastModificationTimestamp) {

    50             this.isReloadNeeded = fileExists && isReloadNeeded;

    51             this.lastModificationTimestamp = lastModificationTimestamp;

    52             this.fileExists = fileExists;

    53         }

    54 

    55         public boolean isFileExists() {

    56             return fileExists;

    57         }

    58 

    59         public boolean isReloadNeeded() {

    60             return isReloadNeeded;

    61         }

    62 

    63         public long getLastModificationTimestamp() {

    64             return lastModificationTimestamp;

    65         }

    66     }

    67 

    68 

    69     private ReloadTracker(Path filePath, long refreshTimeoutMillis) {

    70         this.filePath = filePath;

    71         this.refreshTimeoutMillis = refreshTimeoutMillis;

    72     }

    73 

    74 

    75     public ReloadStatus getReloadStatus() {

    76         boolean fileExists;

    77         var pa = (PrivilegedAction<Boolean>) () -> filePath.toFile().isFile();

    78         fileExists = System.getSecurityManager() == null ? pa.run() : AccessController.doPrivileged(pa);

    79 

    80         long lastModificationTime = -1;

    81         long lastReload = lastRefreshed.get();

    82 

    83         // Do not update lastModification time if file doesn't exist

    84         if (fileExists) {

    85             try {

    86                 var pea = (PrivilegedExceptionAction<Long>) () -> Files.getLastModifiedTime(filePath).toMillis();

    87                 lastModificationTime = System.getSecurityManager() == null ? pea.run()

    88                         : AccessController.doPrivileged(pea);

    89             } catch (Exception e) {

    90                 // In case of Exception the tracked file will be reloaded, ie lastModificationTime == -1

    91             }

    92         }

    93         return new ReloadStatus(fileExists,

    94                 (lastModificationTime != lastSeenChanged.get()) ||

    95                         (System.currentTimeMillis() - lastReload > refreshTimeoutMillis),

    96                 lastModificationTime);

    97     }

    98 

    99     public void updateTimestamps(ReloadStatus rs) {

   100         lastSeenChanged.set(rs.lastModificationTimestamp);

   101         lastRefreshed.set(System.currentTimeMillis());

   102     }

   103 

   104     // Last timestamp when tracked file has been reloaded by consumer of this utility class

   105     private final AtomicLong lastRefreshed = new AtomicLong(-1);

   106     // Last processed FS last modified timestamp

   107     private final AtomicLong lastSeenChanged = new AtomicLong(-1);

   108     // Refresh timeout

   109     private final long refreshTimeoutMillis;

   110     // Path of the tracked file

   111     private final Path filePath;

   112 }