haiyangsun-db commented on code in PR #55611: URL: https://github.com/apache/spark/pull/55611#discussion_r3168887016
########## udf/worker/core/src/main/scala/org/apache/spark/udf/worker/core/WorkerSessionFactory.scala: ########## @@ -0,0 +1,128 @@ +/* + * 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.udf.worker.core + +import java.util.HashMap + +import org.apache.spark.annotation.Experimental +import org.apache.spark.udf.worker.UDFWorkerSpecification +/** + * :: Experimental :: + * Creates [[WorkerSession]] instances for a given + * [[UDFWorkerSpecification]], managing [[WorkerDispatcher]] instances + * and their lifecycle internally. + * + * Dispatchers are cached by spec (protobuf value equality) and reused + * across sessions. The factory tracks the number of active sessions + * per dispatcher. When the last session for a dispatcher is closed, + * the entry is removed and [[onAllDispatcherSessionsClosed]] is + * called. + * + * Thread safety: a single lock guards all map mutations and session + * count changes. The actual [[WorkerDispatcher#createSession]] call + * and the [[onAllDispatcherSessionsClosed]] callback happen outside + * the lock. + * + * Subclasses must implement [[doCreateDispatcher]] to provide a + * concrete dispatcher and [[onAllDispatcherSessionsClosed]] to + * control dispatcher teardown policy. Keeping a dispatcher alive + * after all its sessions have closed should be a conscious decision. + */ +@Experimental +abstract class WorkerSessionFactory { + + private class DispatcherEntry(val dispatcher: WorkerDispatcher) { + var activeSessionCount: Int = 0 + } + + // All access guarded by `synchronized(lock)`. + private val lock = new Object + private val dispatchers = + new HashMap[UDFWorkerSpecification, DispatcherEntry]() + + /** + * Creates a [[WorkerSession]] for the given worker specification + * and optional security scope. + * + * If a dispatcher for this spec already exists it is reused; + * otherwise [[doCreateDispatcher]] is called to create one. + */ + final def createSession( + workerSpec: UDFWorkerSpecification, + securityScope: Option[WorkerSecurityScope] = None + ): WorkerSession = { + val entry = lock.synchronized { + var e = dispatchers.get(workerSpec) + if (e == null) { + e = new DispatcherEntry(doCreateDispatcher(workerSpec)) + dispatchers.put(workerSpec, e) + } + e.activeSessionCount += 1 + e + } + val underlying = entry.dispatcher.createSession(securityScope) + new ManagedWorkerSession(underlying, workerSpec) + } + + /** + * Creates a new [[WorkerDispatcher]] for the given specification. + * Called at most once per structurally distinct spec (until the + * entry is removed after all sessions close). The dispatcher may + * be used for many sessions over its lifetime. + */ + protected def doCreateDispatcher( + workerSpec: UDFWorkerSpecification): WorkerDispatcher + + /** + * Called when the last active session for a dispatcher is closed + * and the entry has been removed from the cache. Subclasses must + * decide what to do with the now-idle dispatcher: close it + * immediately, schedule idle-timeout eviction, etc. + * + * Called outside the lock so subclasses may perform blocking work. + * + * @param dispatcher The dispatcher whose session count reached + * zero. Guaranteed to be a dispatcher returned + * from [[doCreateDispatcher]]. + */ + protected def onAllDispatcherSessionsClosed( + dispatcher: WorkerDispatcher): Unit + + private class ManagedWorkerSession( + underlying: WorkerSession, + workerSpec: UDFWorkerSpecification) + extends DelegatedWorkerSession(underlying) { + + override def close(): Unit = { Review Comment: maybe this logic can also be a contract between session and dispatcher directly, instead of inventing an indirection here. -- 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]
