com.bigdata.ganglia

Class GangliaListener

java.lang.Object

com.bigdata.ganglia.GangliaListener

All Implemented Interfaces:

IGangliaDefaults, Callable<Void>

public class GangliaListener
extends Object
implements Callable<Void>, IGangliaDefaults

Class listens in to the Ganglia UDP protocol, decodes received messages, and dispatches them to an IGangliaMessageHandler.

The decoded messages are reported without any additional translation. The receiver may need to reconcile host names, IGangliaMetadataMessages with those already on hand, and/or reconcile IGangliaMetricMessage with the IGangliaMetadataMessages already on hand. The GangliaListener does NOT perform such operations by design so it maybe used to obtain a faithful transcription of the chatter on the ganglia network.

Field Summary

Fields inherited from interface com.bigdata.ganglia.IGangliaDefaults

BUFFER_SIZE, DEFAULT_DMAX, DEFAULT_GROUP, DEFAULT_PORT, DEFAULT_SLOPE, DEFAULT_TMAX, DEFAULT_UNITS, HEARTBEAT_INTERVAL, INITIAL_DELAY, MONITORING_INTERVAL, QUIET_PERIOD

Constructor Summary

Constructors

Constructor and Description
GangliaListener(IGangliaMessageHandler handler) Listen at the default multicast group address and port.
GangliaListener(InetAddress group, int port, IGangliaMessageDecoder decoder, IGangliaMessageHandler handler) Listen at the specified multicast group address and port.

Method Summary

Methods

Modifier and Type	Method and Description
Void	call() Listens for ganglia messages.
protected IGangliaMessage	decodeRecord(byte[] data, int off, int len) Decode a Ganglia message from the datagram packet.
boolean	isListening() Return true iff the listener is running when this method is invoked.
static void	main(String[] args) Listens to ganglia services on the default multicast address and port and writes out the messages that it observes on stdout.

Methods inherited from class java.lang.Object

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

Constructor Detail

GangliaListener

public GangliaListener(IGangliaMessageHandler handler)
                throws UnknownHostException

Listen at the default multicast group address and port.

Parameters:

handler - The interface to receive the ganglia messages.

Throws:

UnknownHostException

See Also:

IGangliaDefaults.DEFAULT_GROUP, IGangliaDefaults.DEFAULT_PORT

GangliaListener

public GangliaListener(InetAddress group,
               int port,
               IGangliaMessageDecoder decoder,
               IGangliaMessageHandler handler)

Listen at the specified multicast group address and port.

Parameters:

group - The multicast address used by ganglia for hosts to join.

port - The port on which the ganglia services are talking.

decoder - Object responsible for decoding packets.

handler - The interface to receive the ganglia messages.

Method Detail

isListening

public boolean isListening()

Return true iff the listener is running when this method is invoked.

call

public Void call()
          throws Exception

Listens for ganglia messages. Each message is decoded as as it is received. Bad packets are dropped. Valid messages are dispatched using a second thread to avoid latency in the thread which is listening to the ganglia protocol.

Note: This method BLOCKS and does NOT notice an interrupt. This is because JDK 6 does not support multicast NIO. TODO Java 6 does not support non-blocking multicast receive. Write a JDK 7 specific version of class class which uses multicast with non-blocking IO and hence can be interrupted.

Specified by:

call in interface Callable<Void>

Throws:

Exception

See Also:

Multicasting with NIO., MulticastChannel

decodeRecord

protected IGangliaMessage decodeRecord(byte[] data,
                           int off,
                           int len)

Decode a Ganglia message from the datagram packet.

Parameters:

data - The packet data.

off - The offset of the first byte in the packet.

len - The #of bytes in the packet.

Returns:

The decoded record.

main

public static void main(String[] args)
                 throws Exception

Listens to ganglia services on the default multicast address and port and writes out the messages that it observes on stdout.

Parameters:

args -

Throws:

Exception