JvmPauseMonitor (Apache HBase 1.2.12 API)

java.lang.Object
- org.apache.hadoop.hbase.util.JvmPauseMonitor

```
@InterfaceAudience.Private
public class JvmPauseMonitor
extends Object
```
Class which sets up a simple thread which runs in a loop sleeping for a short interval of time. If the sleep takes significantly longer than its target time, it implies that the JVM or host machine has paused processing, which may cause other problems. If such a pause is detected, the thread logs a message. The original JvmPauseMonitor is: ${hadoop-common-project}/hadoop-common/src/main/java/org/apache/hadoop/util/ JvmPauseMonitor.java r1503806 | cmccabe | 2013-07-17 01:48:24 +0800 (Wed, 17 Jul 2013) | 1 line HADOOP-9618. thread which detects GC pauses(Todd Lipcon)

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

private static class JvmPauseMonitor.GcTimes

private class JvmPauseMonitor.Monitor

Nested Classes
Modifier and Type	Class and Description
`private static class`	`JvmPauseMonitor.GcTimes`
`private class`	`JvmPauseMonitor.Monitor`

Field Summary

Fields
Modifier and Type	Field and Description
`private static long`	`INFO_THRESHOLD_DEFAULT`
`private static String`	`INFO_THRESHOLD_KEY`
`private long`	`infoThresholdMs` log INFO if we detect a pause longer than this threshold
`private static org.apache.commons.logging.Log`	`LOG`
`private Thread`	`monitorThread`
`private boolean`	`shouldRun`
`private static long`	`SLEEP_INTERVAL_MS` The target sleep time
`private static long`	`WARN_THRESHOLD_DEFAULT`
`private static String`	`WARN_THRESHOLD_KEY`
`private long`	`warnThresholdMs` log WARN if we detect a pause longer than this threshold

Constructor Summary

Constructors
Constructor and Description

JvmPauseMonitor(org.apache.hadoop.conf.Configuration conf)

Constructors
Constructor and Description
`JvmPauseMonitor(org.apache.hadoop.conf.Configuration conf)`

Method Summary

Methods
Modifier and Type	Method and Description
`private String`	`formatMessage(long extraSleepTime, Map<String,JvmPauseMonitor.GcTimes> gcTimesAfterSleep, Map<String,JvmPauseMonitor.GcTimes> gcTimesBeforeSleep)`
`private Map<String,JvmPauseMonitor.GcTimes>`	`getGcTimes()`
`static void`	`main(String[] args)` Simple 'main' to facilitate manual testing of the pause monitor.
`void`	`start()`
`void`	`stop()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail
- LOG
```
private static final org.apache.commons.logging.Log LOG
```
- SLEEP_INTERVAL_MS
```
private static final long SLEEP_INTERVAL_MS
```
  The target sleep time
  
  See Also:
  Constant Field Values
- warnThresholdMs
```
private final long warnThresholdMs
```
  log WARN if we detect a pause longer than this threshold
- WARN_THRESHOLD_KEY
```
private static final String WARN_THRESHOLD_KEY
```
  See Also:
  Constant Field Values
- WARN_THRESHOLD_DEFAULT
```
private static final long WARN_THRESHOLD_DEFAULT
```
  See Also:
  Constant Field Values
- infoThresholdMs
```
private final long infoThresholdMs
```
  log INFO if we detect a pause longer than this threshold
- INFO_THRESHOLD_KEY
```
private static final String INFO_THRESHOLD_KEY
```
  See Also:
  Constant Field Values
- INFO_THRESHOLD_DEFAULT
```
private static final long INFO_THRESHOLD_DEFAULT
```
  See Also:
  Constant Field Values
- monitorThread
```
private Thread monitorThread
```
- shouldRun
```
private volatile boolean shouldRun
```

Constructor Detail

JvmPauseMonitor

public JvmPauseMonitor(org.apache.hadoop.conf.Configuration conf)

Method Detail

start
```
public void start()
```

stop
```
public void stop()
```

formatMessage

private String formatMessage(long extraSleepTime,
                   Map<String,JvmPauseMonitor.GcTimes> gcTimesAfterSleep,
                   Map<String,JvmPauseMonitor.GcTimes> gcTimesBeforeSleep)

getGcTimes

private Map<String,JvmPauseMonitor.GcTimes> getGcTimes()

main
```
public static void main(String[] args)
                 throws Exception
```
Simple 'main' to facilitate manual testing of the pause monitor. This main function just leaks memory into a list. Running this class with a 1GB heap will very quickly go into "GC hell" and result in log messages about the GC pauses.

Throws:

Exception

Class JvmPauseMonitor

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LOG

SLEEP_INTERVAL_MS

warnThresholdMs

WARN_THRESHOLD_KEY

WARN_THRESHOLD_DEFAULT

infoThresholdMs

INFO_THRESHOLD_KEY

INFO_THRESHOLD_DEFAULT

monitorThread

shouldRun

Constructor Detail

JvmPauseMonitor

Method Detail

start

stop

formatMessage

getGcTimes

main