org.apache.hadoop.metrics
Interface MetricsContext

All Known Implementing Classes:

AbstractMetricsContext, FileContext, GangliaContext, NullContext, NullContextWithUpdateThread

public interface MetricsContext

The main interface to the metrics package.

Field Summary

static int

DEFAULT_PERIOD Default period in seconds at which data is sent to the metrics system.

Method Summary

void	close() Stops monitoring and also frees any buffered data, returning this object to its initial state.
MetricsRecord	createRecord(String recordName) Creates a new MetricsRecord instance with the given recordName.
String	getContextName() Returns the context name.
boolean	isMonitoring() Returns true if monitoring is currently in progress.
void	registerUpdater(Updater updater) Registers a callback to be called at regular time intervals, as determined by the implementation-class specific configuration.
void	startMonitoring() Starts or restarts monitoring, the emitting of metrics records as they are updated.
void	stopMonitoring() Stops monitoring.
void	unregisterUpdater(Updater updater) Removes a callback, if it exists.

Field Detail

DEFAULT_PERIOD

static final int DEFAULT_PERIOD

Default period in seconds at which data is sent to the metrics system.

See Also:

Constant Field Values

Method Detail

getContextName

String getContextName()

Returns the context name.

Returns:

the context name

startMonitoring

void startMonitoring()
                     throws IOException

Starts or restarts monitoring, the emitting of metrics records as they are updated.

Throws:

IOException

stopMonitoring

void stopMonitoring()

Stops monitoring. This does not free any data that the implementation may have buffered for sending at the next timer event. It is OK to call startMonitoring() again after calling this.

See Also:

close()

isMonitoring

boolean isMonitoring()

Returns true if monitoring is currently in progress.

close

void close()

Stops monitoring and also frees any buffered data, returning this object to its initial state.

createRecord

MetricsRecord createRecord(String recordName)

Creates a new MetricsRecord instance with the given recordName. Throws an exception if the metrics implementation is configured with a fixed set of record names and recordName is not in that set.

Parameters:

recordName - the name of the record

Throws:

MetricsException - if recordName conflicts with configuration data

registerUpdater

void registerUpdater(Updater updater)

Registers a callback to be called at regular time intervals, as determined by the implementation-class specific configuration.

Parameters:

updater - object to be run periodically; it should updated some metrics records and then return

unregisterUpdater

void unregisterUpdater(Updater updater)

Removes a callback, if it exists.

Parameters:

updater - object to be removed from the callback list