From 6794ca269b0be470464ed60813219c732ab21f1d Mon Sep 17 00:00:00 2001
From: Santiago Pericas-Geertsen <santiago.pericasgeertsen@oracle.com>
Date: Wed, 12 Feb 2025 10:11:22 -0500
Subject: [PATCH] Some experiments with IdleInputStream.

Signed-off-by: Santiago Pericas-Geertsen <santiago.pericasgeertsen@oracle.com>
---
 .../common/socket/IdleInputStream.java        | 18 ++---
 .../common/socket/IdleInputStreamTest.java    | 79 +++++++++++++++++++
 2 files changed, 85 insertions(+), 12 deletions(-)
 create mode 100644 common/socket/src/test/java/io/helidon/common/socket/IdleInputStreamTest.java

diff --git a/common/socket/src/main/java/io/helidon/common/socket/IdleInputStream.java b/common/socket/src/main/java/io/helidon/common/socket/IdleInputStream.java
index 33b037c8fe0..b5459e23ad8 100644
--- a/common/socket/src/main/java/io/helidon/common/socket/IdleInputStream.java
+++ b/common/socket/src/main/java/io/helidon/common/socket/IdleInputStream.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023 Oracle and/or its affiliates.
+ * Copyright (c) 2023, 2025 Oracle and/or its affiliates.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,7 +20,6 @@
 import java.io.InputStream;
 import java.io.UncheckedIOException;
 import java.util.Objects;
-import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
@@ -105,6 +104,11 @@ boolean isClosed() {
         return closed;
     }
 
+    void endIdle() {
+        idlingThread.cancel(true);
+        idlingThread = null;
+    }
+
     private void handle() {
         try {
             next = upstream.read();
@@ -116,14 +120,4 @@ private void handle() {
             throw new UncheckedIOException(e);
         }
     }
-
-    private void endIdle() {
-        try {
-            idlingThread.get();
-            idlingThread = null;
-        } catch (InterruptedException | ExecutionException e) {
-            closed = true;
-            throw new RuntimeException("Exception in socket monitor thread.", e);
-        }
-    }
 }
diff --git a/common/socket/src/test/java/io/helidon/common/socket/IdleInputStreamTest.java b/common/socket/src/test/java/io/helidon/common/socket/IdleInputStreamTest.java
new file mode 100644
index 00000000000..7884c8c6c8b
--- /dev/null
+++ b/common/socket/src/test/java/io/helidon/common/socket/IdleInputStreamTest.java
@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2025 Oracle and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.helidon.common.socket;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+
+import org.junit.jupiter.api.Test;
+
+class IdleInputStreamTest {
+
+    @Test
+    void testIdleInputStream() throws ExecutionException, InterruptedException {
+        Barrier endBarrier = new Barrier();
+        Barrier startBarrier = new Barrier();
+        BarrierInputStream bis = new BarrierInputStream(startBarrier, endBarrier);
+        IdleInputStream iis = new IdleInputStream(bis, "socketId", "socketId");
+
+        iis.idle();
+        startBarrier.waitOn();      // waits on idle thread to start
+        iis.endIdle();
+        endBarrier.waitOn();        // waits on idle thread interruption
+    }
+
+    static class BarrierInputStream extends InputStream {
+
+        private final Barrier endBarrier;
+        private final Barrier startBarrier;
+
+        BarrierInputStream(Barrier startBarrier, Barrier endBarrier) {
+            this.startBarrier = startBarrier;
+            this.endBarrier = endBarrier;
+        }
+
+        @Override
+        public int read() throws IOException {
+            try {
+                startBarrier.retract();
+                Barrier nextBarrier = new Barrier();
+                nextBarrier.waitOn();
+                return 0;
+            } catch (ExecutionException | InterruptedException e) {
+                e.printStackTrace();
+                endBarrier.retract();
+                return 0;
+            }
+        }
+    }
+
+    /**
+     * A barrier is used to force a thread to wait (block) until it is retracted.
+     */
+    private static class Barrier {
+        private final CompletableFuture<Void> future = new CompletableFuture<>();
+
+        void waitOn() throws ExecutionException, InterruptedException {
+            future.get();
+        }
+
+        void retract() {
+            future.complete(null);
+        }
+    }
+}