[GitHub] [spark] liuzqt commented on a diff in pull request #40982: [SPARK-43300][CORE] NonFateSharingCache wrapper for Guava Cache

["liuzqt (via GitHub)" <gi...@apache.org>]

liuzqt commented on code in PR #40982:
URL: https://github.com/apache/spark/pull/40982#discussion_r1191657688


##########
core/src/test/scala/org/apache/spark/util/NonFateSharingCacheSuite.scala:
##########
@@ -0,0 +1,147 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.spark.util;
+
+import java.util.concurrent.ExecutionException
+import java.util.concurrent.Semaphore
+import java.util.concurrent.atomic.AtomicReference
+
+import com.google.common.cache.CacheBuilder
+import com.google.common.cache.CacheLoader
+
+import org.apache.spark.SparkFunSuite
+
+object NonFateSharingCacheSuite {
+  private val TEST_KEY = "key"
+  private val FAIL_MESSAGE = "loading failed"
+  private val THREAD2_HOLDER = new AtomicReference[Thread](null)
+
+  class TestCacheLoader extends CacheLoader[String, String] {
+    var intentionalFail: ThreadLocal[Boolean] = ThreadLocal.withInitial(() => false)
+    var startLoading = new Semaphore(0)
+
+    def waitUntilThread2Waiting(): Unit = {
+      while (true) {
+        Thread.sleep(100)
+        val t2 = THREAD2_HOLDER.get()
+        if (t2 != null && t2.getState.equals(Thread.State.WAITING)) {
+          return
+        }
+      }
+    }
+
+    override def load(key: String): String = {
+      startLoading.release()
+      if (Thread.currentThread().getName.contains("test-executor1")) {
+        waitUntilThread2Waiting()
+      }
+      if (intentionalFail.get) throw new RuntimeException(FAIL_MESSAGE)
+      key
+    }
+  }
+}
+
+/**
+ * Test non-fate-sharing behavior
+ */
+class NonFateSharingCacheSuite extends SparkFunSuite {
+
+  type WorkerFunc = () => Unit
+
+  import NonFateSharingCacheSuite._
+
+  test("test LoadingCache") {
+    val loader = new TestCacheLoader
+    val loadingCache: NonFateSharingLoadingCache[String, String] =
+      NonFateSharingCache(CacheBuilder.newBuilder.build(loader))
+    val thread1Task: WorkerFunc = () => {
+      loader.intentionalFail.set(true)
+      loadingCache.get(TEST_KEY)
+    }
+    val thread2Task: WorkerFunc = () => {
+      loadingCache.get(TEST_KEY)
+    }
+    testImpl(loadingCache, loader, thread1Task, thread2Task)
+  }
+
+  test("test LoadingCache mix usage of default loader and provided loader") {
+    // Intentionally mix usage of default loader and provided value loader.
+    val loader = new TestCacheLoader
+    val loadingCache: NonFateSharingLoadingCache[String, String] =
+      NonFateSharingCache(CacheBuilder.newBuilder.build(loader))
+    val thread1Task: WorkerFunc = () => {
+      loader.intentionalFail.set(true)
+      loadingCache.get(
+        TEST_KEY,
+        () => loader.load(TEST_KEY)
+      )
+    }
+    val thread2Task: WorkerFunc = () => {
+      loadingCache.get(TEST_KEY)
+    }
+    testImpl(loadingCache, loader, thread1Task, thread2Task)
+  }
+
+  test("test Cache") {
+    val loader = new TestCacheLoader
+    val cache = NonFateSharingCache(CacheBuilder.newBuilder.build[String, String])
+    val thread1Task: WorkerFunc = () => {
+      loader.intentionalFail.set(true)
+      cache.get(
+        TEST_KEY,
+        () => loader.load(TEST_KEY)
+      )
+    }
+    val thread2Task: WorkerFunc = () => {
+      cache.get(
+        TEST_KEY,
+        () => loader.load(TEST_KEY)
+      )
+    }
+    testImpl(cache, loader, thread1Task, thread2Task)
+  }
+
+  def testImpl(
+    cache: NonFateSharingCache[String, String],
+    loader: TestCacheLoader,
+    thread1Task: WorkerFunc,
+    thread2Task: WorkerFunc): Unit = {
+    val executor1 = ThreadUtils.newDaemonSingleThreadExecutor("test-executor1")
+    val executor2 = ThreadUtils.newDaemonSingleThreadExecutor("test-executor2")
+    val f1 = executor1.submit(new Runnable {
+      override def run(): Unit = {
+        thread1Task()
+      }
+    })
+    val f2 = executor2.submit(new Runnable {
+      override def run(): Unit = {
+        loader.startLoading.acquire() // wait until thread1 start loading
+        THREAD2_HOLDER.set(Thread.currentThread())
+        thread2Task()
+      }
+    })

Review Comment:
   I was hitting a overload resolution issue:
   ```
   ambiguous reference to overloaded definition,
   [error] both method submit in class AbstractExecutorService of type [T](x$1: java.util.concurrent.Callable[T])java.util.concurrent.Future[T]
   [error] and  method submit in class AbstractExecutorService of type (x$1: Runnable)java.util.concurrent.Future[_]
   
   ```
   But I can do 
   ```
   val r1: Runnable = () => thread1Task()
   val f1 = executor1.submit(r1)
   ```
   instead
   



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