Groupcast Echoes Sample Application

Author: Pablo Chacin

Version. 1.0

Created: March 07, 2006

(c) Technical University of Catalonya 2006

Overview

The application shows two agents, EchoesServer and EchoesClient, which commnicate in a send/reply model to implement a sort of "ping" command, as provided for TCPIP in most platforms. The EchoClient sends the "ping" messages using a groupcast to all the EchoServers in the neiborghood and registers the response time from each server.

EchoClient and EchoServer agents can be started in different JVMs as they communicate using P2P communication mechanisms.

This application can be considered a version of the Echoes Sample Application

Throught this example we can show how the following functionalities are implemented:

• Crete an agent and pass initialization parameters
• Wait for an agent to complete and get results from it
• Retrieve parameters passed to an agent and pass back results
• Send a groupcast messages
• Joing a groupcast group
• Reply to an message received from other agent
• Schedulle events to be executed in the future and handle them when the time expires
• Report execution metrics that can be externaly analyzed
• Keep a record of agent's the execution by means of log entries

Components

• EchoesClientMainApp: is the main application that starts the EchoClient agent and pass to them the required parameters, as specified below.

  The application receives as command line parameters:

  • Local tcp port to be used by the application (ussualy in the range 8050-8059). Must be unique for all the applications running in the same node (on different JVM), but can be the same across nodes.
  • Name of the local node (for example, "ClietNode").
• EchoesServerMainApp: is the main application that starts the EchoServer agent and pass to them the required parameters, as specified below. This application can be started in different nodes than the client application, or in different JVM in the same node.

  The application receives as command line parameters:

  • Local tcp port to be used by the application (ussualy in the range 8050-8059). Must be unique for all the applications running in the same node (on different JVM), but can be the same across nodes.
  • Name of the local node (for example, "ServerxxNode", where xx differentiates different server nodes).
• EchoServer joins the "Echoes" groupcast group and respond to messsages sent to this group by cliets after waiting for a random delay that simulates the response time of the server. The delay is implemented by a schedulled event with a random delay time. When the event expires, the server replies to the client with the same message it received. The server receives as parameters:
  • Average delay time
  • Variation on the delay time.
• EchoClient groupcasts a requests to the "Echoes" group and records the response time of each server. Upon finalization, calculates the average response time, reports it as a "ResponseTime" metrics and returns as a result argument to the caller application.

  The client receives as parameters:

  • Minumun number of requests expected
  • Maximun time to wait for responses.

Executing the application

• src/ source files
• lib/ libraries required by the application (including libraries required by the middleware)

In Eclipse

1. Import the Echoes project
2. Be sure that under the project's main directory there is a subdirectory called EchoClient and another called EchoServer. If not, create them. If you plan to run more than one instance of the EchoServerMainApp, create one additional subdirectory for each of them (for example, 'EchoServer2', 'EchoServer3' ...)
3. run the class EchoServerMainApp, passing the following command line parameters:
   config.node EchoServer config.port 8051. config.workdirectory ./EchoServer
4. If you plan to execute more than one instance of this class, change these parameters accordingly. Be sure the config.port is unique on the machine and that config.workdirectory maches the name of the working directory you created for each instance.
5. run the class EchoClientMainApp, passing the following command line parameters:
   config.node EchoServer config.port 8059 config.workdirectory ./EchoClient

Execution Results

Client output

After executing the application a trace should be shown in the console. This trace can also be seen in the file log.txt under the client's work directory. The trace should look as follows:


org.catnets.p2pagent.logging.LoggerAgentinitializing trace reporting
Waiting for the agent to complete
< INFO 2006-03-08 16:08:00,660 JxtaConfig:::94> JXTA_HOME=/home/pchacin/workspace/EchoesSample/EchoClient
Timestamp: 1141830480511
Severity: INFO
AgentName: GroupCommunication
Component: org.catnets.p2pagent.groupCommunication.GroupCommunicationAgent
Event: Initializing
Message: Initialized

< INFO 2006-03-08 16:08:05,318 NullConfigurator:::146> JXTA_HOME = /home/pchacin/workspace/EchoesSample/EchoClient
< INFO 2006-03-08 16:08:05,319 NullConfigurator::resetFromResource:361> /home/pchacin/workspace/EchoesSample/EchoClient/PlatformConfig already exists
< INFO 2006-03-08 16:08:05,320 NullConfigurator::resetFromResource:361> /home/pchacin/workspace/EchoesSample/EchoClient/jxta.properties already exists
< INFO 2006-03-08 16:08:05,374 NullConfigurator::adjustLog4JPriority:440> Log4J [user default] requested, not adjusting logging priority
< INFO 2006-03-08 16:08:05,819 NullConfigurator::adjustLog4JPriority:440> Log4J [user default] requested, not adjusting logging priority
Timestamp: 1141830480660
Severity: INFO
AgentName: EchoClient
Component: EchoRequestor
Event: execute
Message: Initiating Agent

Timestamp: 1141830480663
Severity: INFO
AgentName: EchoClient
Component: EchoRequestor
Event: makeRequest
Message: Making requests

Timestamp: 1141830488204
Severity: INFO
AgentName: EchoClient
Component: EchoRequestor
Event: Response received
Message: Request 1 execution time: 7541

Timestamp: 1141830489416
Severity: INFO
AgentName: EchoClient
Component: EchoRequestor
Event: Response received
Message: Request 2 execution time: 8754

Agent has finished
Average echo time: 8147.5
Timestamp: 1141830490695
Severity: INFO
AgentName: EchoClient
Component: EchoClient
Event: Handling timeout
Message: Time out expired. Number of responses: 2


Also, in the client's work directory there should be a file named ResponseTime.txt with a series of rows, each with the response time of each echo request sent by the client to the server. This file should look as follows:

1140714229886,EchoClient,ResponseTime,6565
1140714231382,EchoClient,ResponseTime,7495


Server output

After executing the application a trace should be shown in the console. This trace can also be seen in the file log.txt under the server's work directory. The trace should look as follows:

org.catnets.p2pagent.logging.LoggerAgentinitializing trace reporting
Timestamp: 1141829477408
Severity: INFO
AgentName: EchoServer
Component: EchoServer
Event: execution
Message: Initiating agent

< INFO 2006-03-08 15:51:21,918 NullConfigurator:::146> JXTA_HOME = /home/pchacin/workspace/EchoesSample/EchoServer2
< INFO 2006-03-08 15:51:21,919 NullConfigurator::resetFromResource:361> /home/pchacin/workspace/EchoesSample/EchoServer2/PlatformConfig already exists
< INFO 2006-03-08 15:51:21,923 NullConfigurator::resetFromResource:382> jxta.properties reset /home/pchacin/workspace/EchoesSample/EchoServer2/jxta.properties
< INFO 2006-03-08 15:51:21,982 NullConfigurator::adjustLog4JPriority:440> Log4J [user default] requested, not adjusting logging priority
< INFO 2006-03-08 15:51:22,442 NullConfigurator::adjustLog4JPriority:440> Log4J [user default] requested, not adjusting logging priority

Timestamp: 1141829499910
Severity: INFO
AgentName: OverlayAgent
Component: org.catnets.p2pagent.overlay.OverlayAgent
Event: processQuery
Message: JXTA handler processing a query: 0

Timestamp: 1141829499911
Severity: INFO
AgentName: EchoServer
Component: Server
Event: handle groupcast message
Message: Request Received

Timestamp: 1141829501410
Severity: INFO
AgentName: EchoServer
Component: Server
Event: handleEvent
Message: Event expired