jojochuang commented on code in PR #9328:
URL: https://github.com/apache/ozone/pull/9328#discussion_r2558125435
##########
hadoop-ozone/common/src/main/java/org/apache/hadoop/ozone/om/lock/OzoneManagerLock.java:
##########
@@ -601,36 +604,97 @@ OMLockDetails lockResource(T resource) {
}
}
- private static final class FlatResourceLockManager extends
ResourceLockManager<FlatResource> {
+ private static final class DAGResourceLockManager extends
ResourceLockManager<DAGLeveledResource> {
- private EnumMap<FlatResource, ThreadLocal<Boolean>> acquiredLocksMap = new
EnumMap<>(FlatResource.class);
+ private final EnumMap<DAGLeveledResource, ThreadLocal<Boolean>>
acquiredLocksMap =
+ new EnumMap<>(DAGLeveledResource.class);
+ private final Map<DAGLeveledResource, Set<DAGLeveledResource>>
lockDependentAdjacencySet =
+ new EnumMap<>(DAGLeveledResource.class);
- private FlatResourceLockManager() {
- for (FlatResource flatResource : FlatResource.values()) {
- acquiredLocksMap.put(flatResource, ThreadLocal.withInitial(() ->
Boolean.FALSE));
+ /**
+ * Performs a depth-first traversal (DFS) on the directed acyclic graph
(DAG)
+ * of {@link DAGLeveledResource} objects, processing dependencies and
updating
+ * the lock-dependent adjacency set with resource relationships.
Review Comment:
After executing this method, lockDependentAdjacencySet is populated with the
transitive set of dependent child resources of a given resource type.
##########
hadoop-ozone/common/src/main/java/org/apache/hadoop/ozone/om/lock/DAGLeveledResource.java:
##########
@@ -0,0 +1,77 @@
+/*
+ * 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.hadoop.ozone.om.lock;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Set;
+import java.util.stream.Collectors;
+import org.apache.hadoop.ozone.om.lock.IOzoneManagerLock.Resource;
+
+/**
+ * The {@code DAGLeveledResource} enum represents a set of resources that are
associated with
+ * specific locks in the Ozone Manager Lock mechanism. These resources allow
fine-grained
+ * locking at various levels, ensuring consistent access and management of
system data.
+ * Each resource can optionally define child resources, forming a directed
acyclic graph (DAG)
+ * structure for hierarchical locking.
+ *
+ * The enum implements the {@code Resource} interface, providing a name for
identification and
+ * an associated {@link IOzoneManagerLock.ResourceManager} to manage its
locking behavior.
+ */
Review Comment:
A little more explanation will be nice.
Add: DAGLeveledResource defines the order in which resources can be locked.
Attempting to lock the resources out of order will throw a RuntimeException.
For instance, acquiring SNAPSHOT_DB_CONTENT_LOCK followed by SNAPSHOT_DB_LOCK
is allowed; acquiring SNAPSHOT_LOCAL_DATA_LOCK followed by
SNAPSHOT_DB_CONTENT_LOCK is not permitted.
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