Merge pull request #835 from jglick/TailLog

`TailLog` to support reopened files

src/main/java/org/jvnet/hudson/test/TailLog.java

@@ -29,8 +29,13 @@
 import hudson.model.Job;
 import hudson.model.Run;
 import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
 import java.io.PrintStream;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.attribute.FileTime;
+import java.time.Duration;
 import java.util.concurrent.Semaphore;
 import java.util.concurrent.TimeUnit;
 import org.apache.commons.io.input.Tailer;
@@ -96,7 +101,45 @@ public TailLog withColor(PrefixedOutputStream.AnsiColor color) {
      * @param job a {@link Job#getFullName}
      */
     public TailLog(File buildDirectory, String job, int number) {
-        tailer = Tailer.create(new File(buildDirectory, "log"), new TailerListenerAdapter() {
+        var log = buildDirectory.toPath().resolve("log");
+        tailer = Tailer.builder().setDelayDuration(Duration.ofMillis(50)).setTailable(new Tailer.Tailable() {
+            // like TailablePath
+            @Override public long size() throws IOException {
+                return Files.size(log);
+            }
+            @Override public FileTime lastModifiedFileTime() throws IOException {
+                return Files.getLastModifiedTime(log);
+            }
+            @Override public boolean isNewer(FileTime fileTime) throws IOException {
+                return Files.getLastModifiedTime(log).compareTo(fileTime) > 0;
+            }
+            @Override public Tailer.RandomAccessResourceBridge getRandomAccess(String mode) throws FileNotFoundException {
+                if (!Files.isRegularFile(log)) {
+                    throw new FileNotFoundException(log.toString());
+                }
+                return new Tailer.RandomAccessResourceBridge() {
+                    long ptr;
+                    @Override public long getPointer() throws IOException {
+                        return ptr;
+                    }
+                    @Override public void seek(long pos) throws IOException {
+                        ptr = pos;
+                    }
+                    @Override public int read(byte[] b) throws IOException {
+                        // Unlike RandomAccessFileBridge, not sensitive to file handle:
+                        try (var is = Files.newInputStream(log)) {
+                            is.skipNBytes(ptr);
+                            int r = is.read(b);
+                            if (r > 0) {
+                                ptr += r;
+                            }
+                            return r;
+                        }
+                    }
+                    @Override public void close() throws IOException {}
+                };
+            }
+        }).setTailerListener(new TailerListenerAdapter() {
             PrintStream ps;
             @Override
             public void handle(String line) {
@@ -114,7 +157,7 @@ public void handle(String line) {
                     finished.release();
                 }
             }
-        }, 50);
+        }).get();
     }
 
     public void waitForCompletion() throws InterruptedException {
@@ -123,7 +166,7 @@ public void waitForCompletion() throws InterruptedException {
 
     @Override
     public void close() {
-        tailer.stop();
+        tailer.close();
     }
 
 }

src/test/java/org/jvnet/hudson/test/TailLogTest.java

@@ -0,0 +1,68 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2024 CloudBees, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package org.jvnet.hudson.test;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.PrintWriter;
+import org.apache.commons.io.FileUtils;
+import static org.junit.Assert.assertTrue;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+public final class TailLogTest {
+
+    @Rule public final TemporaryFolder tmp = new TemporaryFolder();
+
+    @Test public void recreatedLog() throws Exception {
+        var dir = tmp.getRoot();
+        try (var tail = new TailLog(dir, "prj", 123).withColor(PrefixedOutputStream.Color.MAGENTA)) {
+            Thread.sleep(1000);
+            var log = new File(dir, "log");
+            try (var os = new FileOutputStream(log); var pw = new PrintWriter(os)) {
+                for (int i = 0; i < 10; i++) {
+                    pw.println(i);
+                    pw.flush();
+                    Thread.sleep(500);
+                }
+            }
+            var log2 = new File(dir, "log.tmp");
+            FileUtils.copyFile(log, log2);
+            FileUtils.delete(log);
+            assertTrue(log2.renameTo(log));
+            try (var os = new FileOutputStream(log, true); var pw = new PrintWriter(os)) {
+                for (int i = 10; i < 20; i++) {
+                    pw.println(i);
+                    pw.flush();
+                    Thread.sleep(500);
+                }
+                pw.println("Finished: WHATEVER");
+            }
+            tail.waitForCompletion();
+        }
+    }
+
+}