cloud-fan commented on code in PR #48037: URL: https://github.com/apache/spark/pull/48037#discussion_r1752024515
########## core/src/main/scala/org/apache/spark/util/LazyTry.scala: ########## @@ -0,0 +1,70 @@ +/* + * 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 scala.util.Try + +/** + * Wrapper utility for a lazy val, with two differences compared to scala behavior: + * + * 1. Non-retrying in case of failure. This wrapper stores the exception in a Try, and will re-throw + * it on the access to `get`. + * In scala, when a `lazy val` field initialization throws an exception, the field remains + * uninitialized, and initialization will be re-attempted on the next access. This also can lead + * to performance issues, needlessly computing something towards a failure, and also can lead to + * duplicated side effects. + * + * 2. Resolving locking issues. + * In scala, when a `lazy val` field is initialized, it grabs the synchronized lock on the + * enclosing object instance. This can lead both to performance issues, and deadlocks. + * For example: + * a) Thread 1 entered a synchronized method, grabbing a coarse lock on the parent object. + * b) Thread 2 get spawned off, and tries to initialize a lazy value on the same parent object + * This causes scala to also try to grab a lock on the parent object. + * c) If thread 1 waits for thread 2 to join, a deadlock occurs. + * This wrapper will only grab a lock on the wrapper itself, and not the parent object. + * + * @param initialize The block of code to initialize the lazy value. + * @tparam T type of the lazy value. + */ +private[spark] class LazyTry[T](initialize: => T) extends Serializable { + private lazy val tryT: Try[T] = Utils.doTryWithCallerStacktrace { initialize } + + /** + * Get the lazy value. If the initialization block threw an exception, it will be re-thrown here. + * The exception will be re-thrown with the current caller's stacktrace. + * An exception with stack trace from when the exception was first thrown can be accessed with + * ``` + * ex.getSuppressed.find { e => + * e.getMessage == org.apache.spark.util.Utils.TRY_WITH_CALLER_STACKTRACE_FULL_STACKTRACE + * } + * ``` + */ + def get: T = Utils.getTryWithCallerStacktrace(tryT) +} + +private[spark] object LazyTry { + /** + * Create a new Lazy instance. + * + * @param initialize The block of code to initialize the lazy value. + * @tparam T type of the lazy value. + * @return a new Lazy instance. Review Comment: ```suggestion * @return a new LazyTry instance. ``` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
