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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.cassandra.utils;
import java.io.*;
import java.lang.management.ManagementFactory;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.text.StrBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Utility to log heap histogram.
*
*/
public final class HeapUtils
{
private static final Logger logger = LoggerFactory.getLogger(HeapUtils.class);
/**
* Generates a HEAP histogram in the log file.
*/
public static void logHeapHistogram()
{
try
{
logger.info("Trying to log the heap histogram using jcmd");
Long processId = getProcessId();
if (processId == null)
{
logger.error("The process ID could not be retrieved. Skipping heap histogram generation.");
return;
}
String jcmdPath = getJcmdPath();
// The jcmd file could not be found. In this case let's default to jcmd in the hope that it is in the path.
String jcmdCommand = jcmdPath == null ? "jcmd" : jcmdPath;
String[] histoCommands = new String[] {jcmdCommand,
processId.toString(),
"GC.class_histogram"};
logProcessOutput(Runtime.getRuntime().exec(histoCommands));
}
catch (Throwable e)
{
logger.error("The heap histogram could not be generated due to the following error: ", e);
}
}
/**
* Retrieve the path to the JCMD executable.
* @return the path to the JCMD executable or null if it cannot be found.
*/
private static String getJcmdPath()
{
// Searching in the JAVA_HOME is safer than searching into System.getProperty("java.home") as the Oracle
// JVM might use the JRE which do not contains jmap.
String javaHome = System.getenv("JAVA_HOME");
if (javaHome == null)
return null;
File javaBinDirectory = new File(javaHome, "bin");
File[] files = javaBinDirectory.listFiles(new FilenameFilter()
{
public boolean accept(File dir, String name)
{
return name.startsWith("jcmd");
}
});
return ArrayUtils.isEmpty(files) ? null : files[0].getPath();
}
/**
* Logs the output of the specified process.
*
* @param p the process
* @throws IOException if an I/O problem occurs
*/
private static void logProcessOutput(Process p) throws IOException
{
try (BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream())))
{
StrBuilder builder = new StrBuilder();
String line;
while ((line = input.readLine()) != null)
{
builder.appendln(line);
}
logger.info(builder.toString());
}
}
/**
* Retrieves the process ID or null
if the process ID cannot be retrieved.
* @return the process ID or null
if the process ID cannot be retrieved.
*/
private static Long getProcessId()
{
long pid = NativeLibrary.getProcessID();
if (pid >= 0)
return pid;
return getProcessIdFromJvmName();
}
/**
* Retrieves the process ID from the JVM name.
* @return the process ID or null
if the process ID cannot be retrieved.
*/
private static Long getProcessIdFromJvmName()
{
// the JVM name in Oracle JVMs is: '@' but this might not be the case on all JVMs
String jvmName = ManagementFactory.getRuntimeMXBean().getName();
try
{
return Long.valueOf(jvmName.split("@")[0]);
}
catch (NumberFormatException e)
{
// ignore
}
return null;
}
/**
* The class must not be instantiated.
*/
private HeapUtils()
{
}
}