hadoop IOStatisticsContextIntegration 源码
haddop IOStatisticsContextIntegration 代码
文件路径:/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/statistics/impl/IOStatisticsContextIntegration.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.fs.statistics.impl;
import java.lang.ref.WeakReference;
import java.util.concurrent.atomic.AtomicLong;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.classification.VisibleForTesting;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.impl.WeakReferenceThreadMap;
import org.apache.hadoop.fs.statistics.IOStatisticsContext;
import static org.apache.hadoop.fs.CommonConfigurationKeys.IOSTATISTICS_THREAD_LEVEL_ENABLED;
import static org.apache.hadoop.fs.CommonConfigurationKeys.IOSTATISTICS_THREAD_LEVEL_ENABLED_DEFAULT;
/**
* A Utility class for IOStatisticsContext, which helps in creating and
* getting the current active context. Static methods in this class allows to
* get the current context to start aggregating the IOStatistics.
*
* Static initializer is used to work out if the feature to collect
* thread-level IOStatistics is enabled or not and the corresponding
* implementation class is called for it.
*
* Weak Reference thread map to be used to keep track of different context's
* to avoid long-lived memory leakages as these references would be cleaned
* up at GC.
*/
public final class IOStatisticsContextIntegration {
private static final Logger LOG =
LoggerFactory.getLogger(IOStatisticsContextIntegration.class);
/**
* Is thread-level IO Statistics enabled?
*/
private static boolean isThreadIOStatsEnabled;
/**
* ID for next instance to create.
*/
public static final AtomicLong INSTANCE_ID = new AtomicLong(1);
/**
* Active IOStatistics Context containing different worker thread's
* statistics. Weak Reference so that it gets cleaned up during GC and we
* avoid any memory leak issues due to long lived references.
*/
private static final WeakReferenceThreadMap<IOStatisticsContext>
ACTIVE_IOSTATS_CONTEXT =
new WeakReferenceThreadMap<>(
IOStatisticsContextIntegration::createNewInstance,
IOStatisticsContextIntegration::referenceLostContext
);
static {
// Work out if the current context has thread level IOStatistics enabled.
final Configuration configuration = new Configuration();
isThreadIOStatsEnabled =
configuration.getBoolean(IOSTATISTICS_THREAD_LEVEL_ENABLED,
IOSTATISTICS_THREAD_LEVEL_ENABLED_DEFAULT);
}
/**
* Static probe to check if the thread-level IO statistics enabled.
*
* @return if the thread-level IO statistics enabled.
*/
public static boolean isIOStatisticsThreadLevelEnabled() {
return isThreadIOStatsEnabled;
}
/**
* Private constructor for a utility class to be used in IOStatisticsContext.
*/
private IOStatisticsContextIntegration() {}
/**
* Creating a new IOStatisticsContext instance for a FS to be used.
* @param key Thread ID that represents which thread the context belongs to.
* @return an instance of IOStatisticsContext.
*/
private static IOStatisticsContext createNewInstance(Long key) {
IOStatisticsContextImpl instance =
new IOStatisticsContextImpl(key, INSTANCE_ID.getAndIncrement());
LOG.debug("Created instance {}", instance);
return instance;
}
/**
* In case of reference loss for IOStatisticsContext.
* @param key ThreadID.
*/
private static void referenceLostContext(Long key) {
LOG.debug("Reference lost for threadID for the context: {}", key);
}
/**
* Get the current thread's IOStatisticsContext instance. If no instance is
* present for this thread ID, create one using the factory.
* @return instance of IOStatisticsContext.
*/
public static IOStatisticsContext getCurrentIOStatisticsContext() {
return isThreadIOStatsEnabled
? ACTIVE_IOSTATS_CONTEXT.getForCurrentThread()
: EmptyIOStatisticsContextImpl.getInstance();
}
/**
* Set the IOStatisticsContext for the current thread.
* @param statisticsContext IOStatistics context instance for the
* current thread. If null, the context is reset.
*/
public static void setThreadIOStatisticsContext(
IOStatisticsContext statisticsContext) {
if (isThreadIOStatsEnabled) {
if (statisticsContext == null) {
// new value is null, so remove it
ACTIVE_IOSTATS_CONTEXT.removeForCurrentThread();
} else {
// the setter is efficient in that it does not create a new
// reference if the context is unchanged.
ACTIVE_IOSTATS_CONTEXT.setForCurrentThread(statisticsContext);
}
}
}
/**
* Get thread ID specific IOStatistics values if
* statistics are enabled and the thread ID is in the map.
* @param testThreadId thread ID.
* @return IOStatisticsContext if found in the map.
*/
@VisibleForTesting
public static IOStatisticsContext getThreadSpecificIOStatisticsContext(long testThreadId) {
LOG.debug("IOStatsContext thread ID required: {}", testThreadId);
if (!isThreadIOStatsEnabled) {
return null;
}
// lookup the weakRef IOStatisticsContext for the thread ID in the
// ThreadMap.
WeakReference<IOStatisticsContext> ioStatisticsSnapshotWeakReference =
ACTIVE_IOSTATS_CONTEXT.lookup(testThreadId);
if (ioStatisticsSnapshotWeakReference != null) {
return ioStatisticsSnapshotWeakReference.get();
}
return null;
}
/**
* A method to enable IOStatisticsContext to override if set otherwise in
* the configurations for tests.
*/
@VisibleForTesting
public static void enableIOStatisticsContext() {
if (!isThreadIOStatsEnabled) {
LOG.info("Enabling Thread IOStatistics..");
isThreadIOStatsEnabled = true;
}
}
}
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