klion26 commented on a change in pull request #10449: [FLINK-7289][state-backend] Integrate RocksDB memory use with managed memory URL: https://github.com/apache/flink/pull/10449#discussion_r354653604
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/memory/SharedResources.java ########## @@ -0,0 +1,172 @@ +/* + * 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.flink.runtime.memory; + +import org.apache.flink.annotation.VisibleForTesting; +import org.apache.flink.util.function.LongFunctionWithException; + +import java.util.HashMap; +import java.util.HashSet; +import java.util.concurrent.locks.ReentrantLock; + +/** + * A map that keeps track of acquired shared resources and handles their allocation disposal. + */ +final class SharedResources { + + private final ReentrantLock lock = new ReentrantLock(); + + private final HashMap<String, LeasedResource<?>> reservedResources = new HashMap<>(); + + /** + * Gets the shared memory resource for the given owner and registers a lease. If the resource + * does not yet exist, it will be created via the given initializer function. + * + * <p>The resource must be released when no longer used. That releases the lease. When all leases are + * released, the resource is disposed. + */ + <T extends AutoCloseable> ResourceAndSize<T> getOrAllocateSharedResource( + String type, + Object leaseHolder, + LongFunctionWithException<T, Exception> initializer, + long sizeForInitialization) throws Exception { + + // We could be stuck on this lock for a while, in cases where another initialization is currently + // happening and the initialization is expensive. + // We lock interruptibly here to allow for faster exit in case of cancellation errors. + try { + lock.lockInterruptibly(); + } + catch (InterruptedException e) { + Thread.currentThread().interrupt(); + throw new MemoryAllocationException("Interrupted while acquiring memory"); + } + + try { + // we cannot use "computeIfAbsent()" here because the computing function may throw an exception. + @SuppressWarnings("unchecked") + LeasedResource<T> resource = (LeasedResource<T>) reservedResources.get(type); + if (resource == null) { + resource = createResource(initializer, sizeForInitialization); + reservedResources.put(type, resource); + } + + resource.addLeaseHolder(leaseHolder); + return resource; + } + finally { + lock.unlock(); + } + } + + /** + * Releases a lease (identified by the lease holder object) for the given type. + * If no further leases exist, the resource is disposed. + * + * @return True, if this was the last lease holder and the resource was disposed. + */ + boolean release(String type, Object leaseHolder) throws Exception { + lock.lock(); + try { + final LeasedResource resource = reservedResources.get(type); + if (resource == null) { + return false; + } + + if (resource.removeLeaseHolder(leaseHolder)) { + reservedResources.remove(type); + resource.dispose(); + return true; + } + + return false; + } + finally { + lock.unlock(); + } + } + + @VisibleForTesting + int getNumResources() { + return reservedResources.size(); + } + + private static <T extends AutoCloseable> LeasedResource<T> createResource( + LongFunctionWithException<T, Exception> initializer, + long size) throws Exception { + + final T resource = initializer.apply(size); + return new LeasedResource<>(resource, size); + } + + // ------------------------------------------------------------------------ + + /** + * A resource handle with size. + */ + interface ResourceAndSize<T extends AutoCloseable> { + + T resourceHandle(); + + long size(); + } + + // ------------------------------------------------------------------------ + + private static final class LeasedResource<T extends AutoCloseable> implements ResourceAndSize<T> { + + private final HashSet<Object> leaseHolders = new HashSet<>(); + + private final T resourceHandle; + + private final long size; + + private boolean disposed; + + private LeasedResource(T resourceHandle, long size) { + this.resourceHandle = resourceHandle; + this.size = size; + } + + public T resourceHandle() { + return resourceHandle; + } + + public long size() { + return size; + } + + void addLeaseHolder(Object leaseHolder) { + assert !disposed; + leaseHolders.add(leaseHolder); + } + + boolean removeLeaseHolder(Object leaseHolder) { + assert !disposed; Review comment: Just curious, when should we use `CheckState` and when to use `assert`, did not find relative things in our [codestyle](https://flink.apache.org/contributing/code-style-and-quality-common.html), as for `assert` seems we need to compile wilth `-ea`, or the assert would not work, only find enable `-ea` in `test_ha_datastream.sh` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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