org.apache.hadoop.metrics.file
Class FileContext

java.lang.Object
  org.apache.hadoop.metrics.spi.AbstractMetricsContext
      org.apache.hadoop.metrics.file.FileContext

All Implemented Interfaces:

MetricsContext

public class FileContext
extends AbstractMetricsContext

Metrics context for writing metrics to a file.

This class is configured by setting ContextFactory attributes which in turn are usually configured through a properties file. All the attributes are prefixed by the contextName. For example, the properties file might contain:

 myContextName.fileName=/tmp/metrics.log
 myContextName.period=5
 

Field Summary

protected static String	FILE_NAME_PROPERTY
protected static String	PERIOD_PROPERTY

Fields inherited from interface org.apache.hadoop.metrics.MetricsContext

DEFAULT_PERIOD

Constructor Summary

FileContext()
Creates a new instance of FileContext

Method Summary

void	emitRecord(String contextName, String recordName, OutputRecord outRec) Emits a metrics record to a file.
void	flush() Flushes the output writer, forcing updates to disk.
String	getFileName() Returns the configured file name, or null.
void	init(String contextName, ContextFactory factory) Initializes the context.
void	startMonitoring() Starts or restarts monitoring, by opening in append-mode, the file specified by the fileName attribute, if specified.
void	stopMonitoring() Stops monitoring, closing the file.

Methods inherited from class org.apache.hadoop.metrics.spi.AbstractMetricsContext

close, createRecord, getAttribute, getAttributeTable, getContextFactory, getContextName, getPeriod, isMonitoring, newRecord, registerUpdater, remove, setPeriod, unregisterUpdater, update

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

FILE_NAME_PROPERTY

protected static final String FILE_NAME_PROPERTY

See Also:

Constant Field Values

PERIOD_PROPERTY

protected static final String PERIOD_PROPERTY

See Also:

Constant Field Values

Constructor Detail

FileContext

public FileContext()

Creates a new instance of FileContext

Method Detail

init

public void init(String contextName,
                 ContextFactory factory)

Description copied from class: AbstractMetricsContext

Initializes the context.

Overrides:

init in class AbstractMetricsContext

getFileName

public String getFileName()

Returns the configured file name, or null.

startMonitoring

public void startMonitoring()
                     throws IOException

Starts or restarts monitoring, by opening in append-mode, the file specified by the fileName attribute, if specified. Otherwise the data will be written to standard output.

Specified by:

startMonitoring in interface MetricsContext

Overrides:

startMonitoring in class AbstractMetricsContext

Throws:

IOException

stopMonitoring

public void stopMonitoring()

Stops monitoring, closing the file.

Specified by:

stopMonitoring in interface MetricsContext

Overrides:

stopMonitoring in class AbstractMetricsContext

See Also:

AbstractMetricsContext.close()

emitRecord

public void emitRecord(String contextName,
                       String recordName,
                       OutputRecord outRec)

Emits a metrics record to a file.

Specified by:

emitRecord in class AbstractMetricsContext

flush

public void flush()

Flushes the output writer, forcing updates to disk.

Overrides:

flush in class AbstractMetricsContext