org.apache.hadoop.metrics.spi
Class AbstractMetricsContext

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

All Implemented Interfaces:

MetricsContext

Direct Known Subclasses:

FileContext, GangliaContext, NullContext, NullContextWithUpdateThread

public abstract class AbstractMetricsContext
extends Object
implements MetricsContext

The main class of the Service Provider Interface. This class should be extended in order to integrate the Metrics API with a specific metrics client library.

This class implements the internal table of metric data, and the timer on which data is to be sent to the metrics system. Subclasses must override the abstract emitRecord method in order to transmit the data.

Field Summary

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

DEFAULT_PERIOD

Constructor Summary

protected

AbstractMetricsContext() Creates a new instance of AbstractMetricsContext

Method Summary

void	close() Stops monitoring and frees buffered data, returning this object to its initial state.
MetricsRecord	createRecord(String recordName) Creates a new AbstractMetricsRecord instance with the given recordName.
protected abstract void	emitRecord(String contextName, String recordName, OutputRecord outRec) Sends a record to the metrics system.
protected void	flush() Called each period after all records have been emitted, this method does nothing.
protected String	getAttribute(String attributeName) Convenience method for subclasses to access factory attributes.
protected Map<String,String>	getAttributeTable(String tableName) Returns an attribute-value map derived from the factory attributes by finding all factory attributes that begin with contextName.tableName.
ContextFactory	getContextFactory() Returns the factory by which this context was created.
String	getContextName() Returns the context name.
int	getPeriod() Returns the timer period.
void	init(String contextName, ContextFactory factory) Initializes the context.
boolean	isMonitoring() Returns true if monitoring is currently in progress.
protected MetricsRecordImpl	newRecord(String recordName) Subclasses should override this if they subclass MetricsRecordImpl.
void	registerUpdater(Updater updater) Registers a callback to be called at time intervals determined by the configuration.
protected void	remove(MetricsRecordImpl record) Called by MetricsRecordImpl.remove().
protected void	setPeriod(int period) Sets the timer period
void	startMonitoring() Starts or restarts monitoring, the emitting of metrics records.
void	stopMonitoring() Stops monitoring.
void	unregisterUpdater(Updater updater) Removes a callback, if it exists.
protected void	update(MetricsRecordImpl record) Called by MetricsRecordImpl.update().

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractMetricsContext

protected AbstractMetricsContext()

Creates a new instance of AbstractMetricsContext

Method Detail

init

public void init(String contextName,
                 ContextFactory factory)

Initializes the context.

getAttribute

protected String getAttribute(String attributeName)

Convenience method for subclasses to access factory attributes.

getAttributeTable

protected Map<String,String> getAttributeTable(String tableName)

Returns an attribute-value map derived from the factory attributes by finding all factory attributes that begin with contextName.tableName. The returned map consists of those attributes with the contextName and tableName stripped off.

getContextName

public String getContextName()

Returns the context name.

Specified by:

getContextName in interface MetricsContext

Returns:

the context name

getContextFactory

public ContextFactory getContextFactory()

Returns the factory by which this context was created.

startMonitoring

public void startMonitoring()
                     throws IOException

Starts or restarts monitoring, the emitting of metrics records.

Specified by:

startMonitoring in interface MetricsContext

Throws:

IOException

stopMonitoring

public void stopMonitoring()

Stops monitoring. This does not free buffered data.

Specified by:

stopMonitoring in interface MetricsContext

See Also:

close()

isMonitoring

public boolean isMonitoring()

Returns true if monitoring is currently in progress.

Specified by:

isMonitoring in interface MetricsContext

close

public void close()

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

Specified by:

close in interface MetricsContext

createRecord

public final MetricsRecord createRecord(String recordName)

Creates a new AbstractMetricsRecord 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.

Specified by:

createRecord in interface MetricsContext

Parameters:

recordName - the name of the record

Throws:

MetricsException - if recordName conflicts with configuration data

newRecord

protected MetricsRecordImpl newRecord(String recordName)

Subclasses should override this if they subclass MetricsRecordImpl.

Parameters:

recordName - the name of the record

Returns:

newly created instance of MetricsRecordImpl or subclass

registerUpdater

public void registerUpdater(Updater updater)

Registers a callback to be called at time intervals determined by the configuration.

Specified by:

registerUpdater in interface MetricsContext

Parameters:

updater - object to be run periodically; it should update some metrics records

unregisterUpdater

public void unregisterUpdater(Updater updater)

Removes a callback, if it exists.

Specified by:

unregisterUpdater in interface MetricsContext

Parameters:

updater - object to be removed from the callback list

emitRecord

protected abstract void emitRecord(String contextName,
                                   String recordName,
                                   OutputRecord outRec)
                            throws IOException

Sends a record to the metrics system.

Throws:

IOException

flush

protected void flush()
              throws IOException

Called each period after all records have been emitted, this method does nothing. Subclasses may override it in order to perform some kind of flush.

Throws:

IOException

update

protected void update(MetricsRecordImpl record)

Called by MetricsRecordImpl.update(). Creates or updates a row in the internal table of metric data.

remove

protected void remove(MetricsRecordImpl record)

Called by MetricsRecordImpl.remove(). Removes all matching rows in the internal table of metric data. A row matches if it has the same tag names and values as record, but it may also have additional tags.

getPeriod

public int getPeriod()

Returns the timer period.

setPeriod

protected void setPeriod(int period)

Sets the timer period