[commons-io] 02/02: Allow start the tailer thread to start on a custom executor service.

[gg...@apache.org]

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ggregory pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/commons-io.git

commit c93030ac0d20a7bc455207cca04b404187b310a1
Author: Gary Gregory <ga...@gmail.com>
AuthorDate: Mon May 8 08:48:41 2023 -0400

    Allow start the tailer thread to start on a custom executor service.
    
    TODO: The work is scheduled manually but at least you can allocate the thread from an application thread pool. Consider using a scheduled executor service as a future enhancement.
---
 .../java/org/apache/commons/io/input/Tailer.java   | 33 ++++++++++++++++++++--
 .../org/apache/commons/io/input/TailerTest.java    |  7 ++++-
 2 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/input/Tailer.java b/src/main/java/org/apache/commons/io/input/Tailer.java
index 121f981c..a58d20f2 100644
--- a/src/main/java/org/apache/commons/io/input/Tailer.java
+++ b/src/main/java/org/apache/commons/io/input/Tailer.java
@@ -34,6 +34,8 @@ import java.nio.file.attribute.FileTime;
 import java.time.Duration;
 import java.util.Arrays;
 import java.util.Objects;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.ThreadUtils;
@@ -160,6 +162,7 @@ public class Tailer implements Runnable, AutoCloseable {
      *   .setPath(path)
      *   .setCharset(StandardCharsets.UTF_8)
      *   .setDelayDuration(Duration.ofSeconds(1))
+     *   .setExecutorService(Executors.newSingleThreadExecutor(Builder::newDaemonThread))
      *   .setReOpen(false)
      *   .setStartThread(true)
      *   .setTailable(tailable)
@@ -172,25 +175,38 @@ public class Tailer implements Runnable, AutoCloseable {
      */
     public static class Builder extends AbstractStreamBuilder<Tailer, Builder> {
 
+        /**
+         * Creates a new daemon thread.
+         *
+         * @param runnable the thread's runnable.
+         * @return a new daemon thread.
+         */
+        private static Thread newDaemonThread(final Runnable runnable) {
+            final Thread thread = new Thread(runnable, "commons-io-tailer");
+            thread.setDaemon(true);
+            return thread;
+        }
+
         private Tailable tailable;
         private TailerListener tailerListener;
         private Duration delayDuration = Duration.ofMillis(DEFAULT_DELAY_MILLIS);
         private boolean end;
         private boolean reOpen;
         private boolean startThread = true;
+        private ExecutorService executorService = Executors.newSingleThreadExecutor(Builder::newDaemonThread);
 
         /**
          * Builds and starts a new configured instance.
          *
+         * The tailer is started if {@code startThread} is true.
+         *
          * @return a new configured instance.
          */
         @Override
         public Tailer get() {
             final Tailer tailer = new Tailer(tailable, getCharset(), tailerListener, delayDuration, end, reOpen, getBufferSize());
             if (startThread) {
-                final Thread thread = new Thread(tailer);
-                thread.setDaemon(true);
-                thread.start();
+                executorService.submit(tailer);
             }
             return tailer;
         }
@@ -206,6 +222,17 @@ public class Tailer implements Runnable, AutoCloseable {
             return this;
         }
 
+        /**
+         * Sets an executor service to use when startThread is true.
+         *
+         * @param executorService
+         * @return this
+         */
+        public Builder setExecutorService(final ExecutorService executorService) {
+            this.executorService = executorService;
+            return this;
+        }
+
         /**
          * Sets the origin.
          *
diff --git a/src/test/java/org/apache/commons/io/input/TailerTest.java b/src/test/java/org/apache/commons/io/input/TailerTest.java
index d35e9f92..a6315eba 100644
--- a/src/test/java/org/apache/commons/io/input/TailerTest.java
+++ b/src/test/java/org/apache/commons/io/input/TailerTest.java
@@ -43,6 +43,7 @@ import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 
@@ -244,7 +245,11 @@ public class TailerTest {
         final File file = new File(temporaryFolder, "tailer-create-with-delay-and-from-start-with-reopen-and-buffersize-and-charset.txt");
         createFile(file, 0);
         final TestTailerListener listener = new TestTailerListener(1);
-        try (Tailer tailer = Tailer.builder().setTailable(new NonStandardTailable(file)).setTailerListener(listener).get()) {
+        try (Tailer tailer = Tailer.builder()
+                .setExecutorService(Executors.newSingleThreadExecutor())
+                .setTailable(new NonStandardTailable(file))
+                .setTailerListener(listener)
+                .get()) {
             assertTrue(tailer.getTailable() instanceof NonStandardTailable);
             validateTailer(listener, file);
         }