fix: restore thread interrupt status after catching InterruptedException

This addresses issue #998 where Logback catches InterruptedException
without re-interrupting the thread, potentially causing caller threads
to lose their interruption status.

Changes:
- AbstractSocketAppender.append() and .connectSocketAndDispatchEvents()
- ConcurrentServerRunner.run()
- AsyncAppenderBase.Worker.run()
- DefaultShutdownHook.run()
- Example classes (ConsolePluginClient, NumberCruncherServer)

Also clears any prior interrupt in AsyncAppenderBaseTest to ensure
test stability.

All existing tests pass.

Author: Zjianru

logback-core/src/main/java/ch/qos/logback/core/AsyncAppenderBase.java

@@ -302,6 +302,7 @@ public void run() {
                         aai.appendLoopOnAppenders(e);
                     }
                 } catch (InterruptedException e1) {
+                    Thread.currentThread().interrupt();
                     // exit if interrupted
                     break;
                 }

logback-core/src/main/java/ch/qos/logback/core/hook/DefaultShutdownHook.java

@@ -62,6 +62,7 @@ public void run() {
             try {
                 Thread.sleep(delay.getMilliseconds());
             } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
             }
         }
         super.stop();

logback-core/src/main/java/ch/qos/logback/core/net/AbstractSocketAppender.java

@@ -188,6 +188,7 @@ protected void append(E event) {
                 addInfo("Dropping event due to timeout limit of [" + eventDelayLimit + "] being exceeded");
             }
         } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
             addError("Interrupted while appending event to SocketAppender", e);
         }
     }
@@ -211,6 +212,7 @@ private void connectSocketAndDispatchEvents() {
                 }
             }
         } catch (InterruptedException ex) {
+            Thread.currentThread().interrupt();
             assert true; // ok... we'll exit now
         }
         addInfo("shutting down");

logback-core/src/main/java/ch/qos/logback/core/net/server/ConcurrentServerRunner.java

@@ -145,6 +145,7 @@ public void run() {
                 }
             }
         } catch (InterruptedException ex) {
+            Thread.currentThread().interrupt();
             assert true; // ok... we'll shut down
         } catch (Exception ex) {
             addError("listener: " + ex);

logback-core/src/test/java/ch/qos/logback/core/AsyncAppenderBaseTest.java

@@ -220,6 +220,7 @@ public void workerThreadFlushesOnStop() throws InterruptedException {
     @Test
     public void stopExitsWhenMaxRuntimeReached() throws InterruptedException {
         int maxFlushTime = 1; // runtime of 0 means wait forever, so use 1 ms instead
+        Thread.interrupted(); // clear any prior interrupt to ensure test stability
         int loopLen = 10;
         ListAppender<Integer> la = delayingListAppender;
         asyncAppenderBase.addAppender(la);

logback-examples/src/main/java/chapters/appenders/socket/ConsolePluginClient.java

@@ -110,6 +110,7 @@ public void run() {
                 try {
                     Thread.sleep(SLEEP);
                 } catch (InterruptedException e) {
+                    Thread.currentThread().interrupt();
                     e.printStackTrace();
                 }
             }

logback-examples/src/main/java/chapters/mdc/NumberCruncherServer.java

@@ -118,6 +118,7 @@ public static void delay(int millis) {
         try {
             Thread.sleep(millis);
         } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
         }
     }