hadoop NameNodeResourcePolicy 源码
haddop NameNodeResourcePolicy 代码
文件路径：/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeResourcePolicy.java
/**
* 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.hdfs.server.namenode;
import java.util.Collection;
import org.apache.hadoop.classification.InterfaceAudience;
/**
* Given a set of checkable resources, this class is capable of determining
* whether sufficient resources are available for the NN to continue operating.
*/
@InterfaceAudience.Private
final class NameNodeResourcePolicy {
/**
* Return true if and only if there are sufficient NN
* resources to continue logging edits.
*
* @param resources the collection of resources to check.
* @param minimumRedundantResources the minimum number of redundant resources
* required to continue operation.
* @return true if and only if there are sufficient NN resources to
* continue logging edits.
*/
static boolean areResourcesAvailable(
Collection<? extends CheckableNameNodeResource> resources,
int minimumRedundantResources) {
// TODO: workaround:
// - during startup, if there are no edits dirs on disk, then there is
// a call to areResourcesAvailable() with no dirs at all, which was
// previously causing the NN to enter safemode
if (resources.isEmpty()) {
return true;
}
int requiredResourceCount = 0;
int redundantResourceCount = 0;
int disabledRedundantResourceCount = 0;
for (CheckableNameNodeResource resource : resources) {
if (!resource.isRequired()) {
redundantResourceCount++;
if (!resource.isResourceAvailable()) {
disabledRedundantResourceCount++;
}
} else {
requiredResourceCount++;
if (!resource.isResourceAvailable()) {
// Short circuit - a required resource is not available.
return false;
}
}
}
if (redundantResourceCount == 0) {
// If there are no redundant resources, return true if there are any
// required resources available.
return requiredResourceCount > 0;
} else {
return redundantResourceCount - disabledRedundantResourceCount >=
minimumRedundantResources;
}
}
}
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