org.javagroups.protocols
Class PERF

java.lang.Object
  |
  +--org.javagroups.stack.Protocol
        |
        +--org.javagroups.protocols.PERF

public class PERF
extends Protocol

Measures time taken by each protocol to process a message. PERF has to be the top protocol in a stack. It adds a special header to the message which travels with the message. Upon initialization, PERF creates a ProtocolObserver for each protocol layer in the stack. That observer notes the time taken for a message to travel through the layer it observes, and records the start time, end time and total time in the message itself (in the header created by PERF). When a message is received by PERF, the statistics for the message are appended to a file (or displayed in a GUI (not yet done)).

Because of different wall times between different machines, PERF should only be used for members in the same JVM. For members in different processes, physical clocks have to be synchronized: if they are only a few milliseconds aprt, the values will be incorrect. For example, to write all performance data to a file, do the following:

  1. Set tracing to on, e.g. trace=true in javagroups.properties
  2. Add a trace statement for PERF.up(): trace0=PERF.up DEBUG /tmp/trace.perf. This will write all trace output to the given file.

Version:
$Revision: 1.6 $
Author:
Bela Ban Oct 2001

Field Summary
 
Fields inherited from class org.javagroups.stack.Protocol
down_handler, down_prot, down_queue, down_thread, down_thread_prio, observer, props, stack, up_handler, up_prot, up_queue, up_thread, up_thread_prio
 
Constructor Summary
PERF()
           
 
Method Summary
 void down(Event evt)
          An event is to be sent down the stack.
 java.lang.String getName()
          All protocol names have to be unique !
 boolean setProperties(java.util.Properties props)
          Configures the protocol initially.
 void start()
          This method is called on a Channel.connect(String).
 void up(Event evt)
          An event was received from the layer below.
 
Methods inherited from class org.javagroups.stack.Protocol
destroy, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, init, passDown, passUp, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setUpProtocol, startDownHandler, startUpHandler, stop, stopInternal
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

PERF

public PERF()
Method Detail

getName

public java.lang.String getName()
All protocol names have to be unique !

Specified by:
getName in class Protocol

setProperties

public boolean setProperties(java.util.Properties props)
Description copied from class: Protocol
Configures the protocol initially. A configuration string consists of name=value items, separated by a ';' (semicolon), e.g.:
 "loopback=false;unicast_inport=4444"
 

Overrides:
setProperties in class Protocol

start

public void start()
           throws java.lang.Exception
Description copied from class: Protocol
This method is called on a Channel.connect(String). Starts work. Protocols are connected and queues are ready to receive events. Will be called from bottom to top. This call will replace the START and START_OK events.

Overrides:
start in class Protocol
Throws:
java.lang.Exception - Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, so Channel.connect(String) will throw an exception

up

public void up(Event evt)
Description copied from class: Protocol
An event was received from the layer below. Usually the current layer will want to examine the event type and - depending on its type - perform some computation (e.g. removing headers from a MSG event type, or updating the internal membership list when receiving a VIEW_CHANGE event). Finally the event is either a) discarded, or b) an event is sent down the stack using passDown() or c) the event (or another event) is sent up the stack using passUp().

Overrides:
up in class Protocol

down

public void down(Event evt)
Description copied from class: Protocol
An event is to be sent down the stack. The layer may want to examine its type and perform some action on it, depending on the event's type. If the event is a message MSG, then the layer may need to add a header to it (or do nothing at all) before sending it down the stack using passDown(). In case of a GET_ADDRESS event (which tries to retrieve the stack's address from one of the bottom layers), the layer may need to send a new response event back up the stack using passUp().

Overrides:
down in class Protocol


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