org.apache.hadoop.hdfs.server.protocol.SlowPeerReports Maven / Gradle / Ivy
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/**
* 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.protocol;
import io.prestosql.hadoop.$internal.com.google.common.collect.ImmutableMap;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.util.Map;
/**
* A class that allows a DataNode to communicate information about all
* its peer DataNodes that appear to be slow.
*
* The wire representation of this structure is a list of
* SlowPeerReportProto messages.
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
public final class SlowPeerReports {
/**
* A map from the DataNode's DataNodeUUID to its aggregate latency
* as seen by the reporting node.
*
* The exact choice of the aggregate is opaque to the NameNode but it
* should be chosen consistently by all DataNodes in the cluster.
* Examples of aggregates are 90th percentile (good) and mean (not so
* good).
*
* The NameNode must not attempt to interpret the aggregate latencies
* beyond exposing them as a diagnostic. e.g. metrics. Also, comparing
* latencies across reports from different DataNodes may not be not
* meaningful and must be avoided.
*/
@Nonnull
private final Map slowPeers;
/**
* An object representing a SlowPeerReports with no entries. Should
* be used instead of null or creating new objects when there are
* no slow peers to report.
*/
public static final SlowPeerReports EMPTY_REPORT =
new SlowPeerReports(ImmutableMap.of());
private SlowPeerReports(Map slowPeers) {
this.slowPeers = slowPeers;
}
public static SlowPeerReports create(
@Nullable Map slowPeers) {
if (slowPeers == null || slowPeers.isEmpty()) {
return EMPTY_REPORT;
}
return new SlowPeerReports(slowPeers);
}
public Map getSlowPeers() {
return slowPeers;
}
public boolean haveSlowPeers() {
return slowPeers.size() > 0;
}
/**
* Return true if the two objects represent the same set slow peer
* entries. Primarily for unit testing convenience.
*/
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (!(o instanceof SlowPeerReports)) {
return false;
}
SlowPeerReports that = (SlowPeerReports) o;
return slowPeers.equals(that.slowPeers);
}
@Override
public int hashCode() {
return slowPeers.hashCode();
}
}