[tomcat] 02/03: Alternative fix for PR #453 - lost log messages on shutdown

[markt]

This is an automated email from the ASF dual-hosted git repository.

markt pushed a commit to branch 9.0.x
in repository https://gitbox.apache.org/repos/asf/tomcat.git

commit a224cbdb603c29a63c14a3f8b921b26870222f86
Author: Mark Thomas <ma...@apache.org>
AuthorDate: Thu Nov 25 14:04:55 2021 +0000

    Alternative fix for PR #453 - lost log messages on shutdown
---
 java/org/apache/juli/AsyncFileHandler.java | 40 ++++++++++++++++++++++++++++++
 webapps/docs/changelog.xml                 |  4 +++
 2 files changed, 44 insertions(+)

diff --git a/java/org/apache/juli/AsyncFileHandler.java 
b/java/org/apache/juli/AsyncFileHandler.java
index e947456..e1ac89b 100644
--- a/java/org/apache/juli/AsyncFileHandler.java
+++ b/java/org/apache/juli/AsyncFileHandler.java
@@ -18,6 +18,7 @@ package org.apache.juli;
 
 import java.util.concurrent.LinkedBlockingDeque;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.logging.LogRecord;
 /**
  * A {@link FileHandler} implementation that uses a queue of log entries.
@@ -95,6 +96,7 @@ public class AsyncFileHandler extends FileHandler {
             }
             closed = true;
         }
+        LoggerThread.deregisterHandler();
         super.close();
     }
 
@@ -109,6 +111,7 @@ public class AsyncFileHandler extends FileHandler {
             }
             closed = false;
         }
+        LoggerThread.registerHandler();
         super.open();
     }
 
@@ -158,6 +161,43 @@ public class AsyncFileHandler extends FileHandler {
     }
 
     protected static class LoggerThread extends Thread {
+
+        /*
+         * Implementation note: Use of this count could be extended to
+         * start/stop the LoggerThread but that would require careful locking 
as
+         * the current size of the queue also needs to be taken into account 
and
+         * there are lost of edge cases when rapidly starting and stopping
+         * handlers.
+         */
+        private static final AtomicInteger handlerCount = new AtomicInteger();
+
+        public static void registerHandler() {
+            handlerCount.incrementAndGet();
+        }
+
+        public static void deregisterHandler() {
+            int newCount = handlerCount.decrementAndGet();
+            if (newCount == 0) {
+                try {
+                    Thread dummyHook = new Thread();
+                    Runtime.getRuntime().addShutdownHook(dummyHook);
+                    Runtime.getRuntime().removeShutdownHook(dummyHook);
+                } catch (IllegalStateException ise) {
+                    // JVM is shutting down.
+                    // Allow up to 10s for for the queue to be emptied
+                    int sleepCount = 0;
+                    while (!AsyncFileHandler.queue.isEmpty() && sleepCount < 
10000) {
+                        try {
+                            Thread.sleep(1);
+                        } catch (InterruptedException e) {
+                            // Ignore
+                        }
+                        sleepCount++;
+                    }
+                }
+            }
+        }
+
         public LoggerThread() {
             this.setDaemon(true);
             this.setName("AsyncFileHandlerWriter-" + 
System.identityHashCode(this));
diff --git a/webapps/docs/changelog.xml b/webapps/docs/changelog.xml
index c163c15..cc1ff07 100644
--- a/webapps/docs/changelog.xml
+++ b/webapps/docs/changelog.xml
@@ -119,6 +119,10 @@
         Document conditions under which the <code>AprLifecycleListener</code>
         can be used to avoid JVM crashes. (michaelo)
       </docs>
+      <fix>
+        Refactor the <code>AsyncFileHandler</code> to reduce the possibility of
+        log messages being lost on shutdown. (markt)
+      </fix>
     </changelog>
   </subsection>
   <subsection name="Coyote">

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