Add missing files.

2 files changed, 106 insertions, 0 deletions

diff --git a/vespajlib/src/main/java/com/yahoo/concurrent/CachedThreadPoolWithFallback.java b/vespajlib/src/main/java/com/yahoo/concurrent/CachedThreadPoolWithFallback.java
new file mode 100644
index 00000000000..42e86aad1ba
--- /dev/null
+++ b/vespajlib/src/main/java/com/yahoo/concurrent/CachedThreadPoolWithFallback.java
@@ -0,0 +1,63 @@
+// Copyright 2020 Oath Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+package com.yahoo.concurrent;
+
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * An executor that will first try a bounded cached threadpool before falling back to a unbounded
+ * single threaded threadpool that will take over dispatching to the primary pool.
+ *
+ */
+public class CachedThreadPoolWithFallback implements AutoCloseable, Executor {
+    private final ExecutorService primary;
+    private final ExecutorService secondary;
+    public CachedThreadPoolWithFallback(String baseName, int corePoolSize, int maximumPoolSize, long keepAlimeTime, TimeUnit timeUnit) {
+        primary = new ThreadPoolExecutor(corePoolSize, maximumPoolSize, keepAlimeTime, timeUnit,
+                new SynchronousQueue<>(), ThreadFactoryFactory.getDaemonThreadFactory(baseName + ".primary"));
+        secondary = Executors.newSingleThreadExecutor(ThreadFactoryFactory.getDaemonThreadFactory(baseName + ".secondary"));
+    }
+    @Override
+    public void execute(Runnable command) {
+        try {
+            primary.execute(command);
+        } catch (RejectedExecutionException e1) {
+            secondary.execute(() -> retryForever(command));
+        }
+    }
+    private void retryForever(Runnable command) {
+        while (true) {
+            try {
+                primary.execute(command);
+                return;
+            } catch (RejectedExecutionException rejected) {
+                try {
+                    Thread.sleep(1);
+                } catch (InterruptedException silenced) { }
+            }
+        }
+    }
+
+    @Override
+    public void close() {
+        secondary.shutdown();
+        join(secondary);
+        primary.shutdown();
+        join(primary);
+    }
+    private static void join(ExecutorService executor) {
+        while (true) {
+            try {
+                if (executor.awaitTermination(60, TimeUnit.SECONDS)) {
+                    return;
+                }
+            } catch (InterruptedException e) {}
+        }
+    }
+}
diff --git a/vespajlib/src/test/java/com/yahoo/concurrent/CachedThreadPoolWithFallbackTest.java b/vespajlib/src/test/java/com/yahoo/concurrent/CachedThreadPoolWithFallbackTest.java
new file mode 100644
index 00000000000..52e17631a34
--- /dev/null
+++ b/vespajlib/src/test/java/com/yahoo/concurrent/CachedThreadPoolWithFallbackTest.java
@@ -0,0 +1,43 @@
+// Copyright 2020 Oath Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+package com.yahoo.concurrent;
+
+import org.junit.Test;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
+
+import static org.junit.Assert.assertEquals;
+
+public class CachedThreadPoolWithFallbackTest {
+    private static void countAndBlock(AtomicLong counter, long waitLimit) {
+        counter.incrementAndGet();
+        try {
+            synchronized (counter) {
+                while (counter.get() < waitLimit) {
+                    counter.wait();
+                }
+            }
+        } catch (InterruptedException e) {}
+    }
+
+    @Test
+    public void testThatTaskAreQueued() throws InterruptedException {
+        CachedThreadPoolWithFallback executor = new CachedThreadPoolWithFallback("test", 1, 30, 1, TimeUnit.SECONDS);
+        AtomicLong counter = new AtomicLong(0);
+        for (int i = 0; i < 1000; i++) {
+            executor.execute(() -> countAndBlock(counter, 100));
+        }
+        while (counter.get() < 30) {
+            Thread.sleep(1);
+        }
+        Thread.sleep(1);
+        assertEquals(30L, counter.get());
+        counter.set(100);
+        synchronized (counter) {
+            counter.notifyAll();
+        }
+        executor.close();
+        assertEquals(1070L, counter.get());
+    }
+}