Project JXTA
Instructor: Dr. Erdogan Dogdu
Presented by: Liu Shuai
http://tinman.cs.gsu.edu/~cscsnlx/ProjectJXTA.ppt
Outline
Introduction - what is JXTA
Goal - what JXTA is aiming at
Structure - how JXTA is built
Protocols - what protocols JXTA has
Implementation – JXTA programming in Java
Applications - what can be done with JXTA
Introduction
started by Sun's Chief Scientist Bill Joy
JXTA is pronounced as “juxta” , is short for juxtapose, as in side by side.
an effort to create a common platform for building distributed services and applications, especially for P2P networking.
What is P2P?
Server-Client model
What is P2P? (Cont.)
Problem with Server-Client Model Scalability
As the number of users increases, there is a higher demand for computing power, storage space, and bandwidth associated with the server-side
Reliability The whole network will depend on the highly
loaded server to function properly
What is P2P? (Cont.)
Peer-to-Peer model
What is P2P? (Cont.)
Advantage of P2P model1. The system is based on the direct communication
between peers 2. There is zero reliance on centralized serviced or
resources for operations 3. The system can survive extreme changes in network
composition 4. They thrive in a network with heterogeneous
environment 5. This model is highly scalable
Goals
Interoperability — JXTA technology is designed to enable peers providing
various P2P services to locate each other and communicate with each other.
Platform independence — JXTA technology is designed to be independent of
programming languages, transport protocols, and deployment platforms.
Ubiquity — JXTA technology is designed to be accessible by any
device with a digital heartbeat, not just PCs or a specific deployment platform.
JXTA Core
JXTA Services
JXTA Applications
Structure
Any Peer on the Web (Desktop, cell phone, PDA, Server)
Security
Peer Groups Peer Pipes Peer Monitoring
JXTA Community Services SunJXTA Services
JXTA Community Applications Sun Applications
JXTAShell
PeerCommands
Technology Concepts
Peer Any networked device that implements one or more of the
JXTA protocols
Peer group A collection of peers that have agreed on a common set of
services. Each peer group can establish its own membership policy One peer can belong to more than one peer group
Advertisement An XML-structured format file describing all existing resource,
such as peer, peer group, pipe, service.
Technology Concepts(Cont.)
Message A set of name/value pairs sent between JXTA peers.
Pipe Message transfer mechanism for service
communication A message queue supporting create, open, close,
delete, send and receive operations
Protocol
JXTA is a set of six protocols Peer Discovery Protocol - find peers, groups, advertisements
Peer Resolver Protocol - send/receive search queries for peers
Peer Information Protocol - learn peers’ status/properties
Peer Membership Protocol - sign in, sign out, authentication
Pipe Binding Protocol - pipe advertisement to pipe endpoint
Endpoint Routing Protocol - available routes to destination
Implementation
JXTA in Java JXTA Standard platform for JDK1.3 PJAVA for Personal Java JXME for J2ME (CLDC/MIDP)
Implementation in other language including C Perl 5.0 Python Ruby Smalltalk
Application
Create a group of peers that provide a serviceSecurely communicate with other peers on the networkFind other peers on the network with dynamic discovery across firewallsEasily share documents with anyone across the networkFind up to the minute content at network sitesMonitor peer activities remotely
Application - examples
Connected game/chat systems so that multiple people in multiple locations can locate each other, send messages securely.
Distributed file caching/knowledge base for data sharing. To share and search file/media over the network
A sample programpublic class DiscoveryDemo implements DiscoveryListener {
static PeerGroup netPeerGroup = null;
private DiscoveryService discovery;
PeerAdvertisement peerAdv;
public DiscoveryDemo() { . . . }
// method to start the JXTA platform
private void startJxta() {
try {
netPeerGroup = PeerGroupFactory.newNetPeerGroup();
}catch ( PeerGroupException e) { ... }
// Get the discovery service from our peer group
discovery = netPeerGroup.getDiscoveryService();
}
A sample program(cont.)//This thread loops forever discovering peers every minute, and displaying the results.
public void run() {
try {
// Add ourselves as a DiscoveryListener for DiscoveryResponse events
discovery.addDiscoveryListener(this);
while (true) {
System.out.println("Sending a Discovery Message");
// look for any peer
discovery.getRemoteAdvertisements(null, DiscoveryService.PEER,null, null, 5, null);
// wait a bit before sending next discovery message
try { Thread.sleep(10 * 1000); } catch(Exception e) { ... }
} //end while
} catch(Exception e) { ... }
}
A sample program(cont.)public void discoveryEvent(DiscoveryEvent ev) {
DiscoveryResponseMsg res = ev.getResponse();
String aRes = res.getPeerAdv();
try {
InputStream is = new ByteArrayInputStream( (aRes).getBytes() );
peerAdv = (PeerAdvertisement) AdvertisementFactory.newAdvertisement(new MimeMediaType( "text/xml" ), is);
System.out.println (" [ Got a Discovery Response ["+ res.getResponseCount()+ " elements] from peer : " + peerAdv.getName() +" ]");
} catch (java.io.IOException e) { ... }
Enumeration enum = res.getResponses(); String str=null;
PeerAdvertisement newAdv=null;
A sample program(cont.) while (enum.hasMoreElements()) {
try {
str = (String) enum.nextElement();
newAdv =(PeerAdvertisement) AdvertisementFactory.newAdvertisement (new MimeMediaType ("text/xml"), new
ByteArrayInputStream(str.getBytes()));
System.out.println(" Peer name = " + newAdv.getName());
} catch (java.io.IOException e) { ... } }
} // end while
}
A sample program(cont.) static public void main(String args[]) {
DiscoveryDemo myapp = new DiscoveryDemo();
myapp.startJxta();
myapp.run();
}
}
Reference
L. Gong, "Sun's Project JXTA: A technology Overview," http://www.jxta.org/project/www/docs/TechOverview.pdf
'Project JXTA': A Technology Overview, JavaOne 2001
Project JXTA: Java™ Programmer’s Guide http://www.jxta.org
Creating JXTA Systems
Instructor: Dr. Erdogan Dogdu
Presented by: Yan Gu
Outline
Application level design and architecture a top-down look at Jxta
A distributed data collection problem.
Analyze and design a solution through Jxta
How Jxta changes the networking landscape by juxtaposition
Jxta Service and Client
A specific example
Create a large-scale distributed weather data collection and analysis system.
Collectors: Are weather data collection points Dispersed all over the world Not all of them connected directly to the Internet May go online or offline at anytime.
Concentrator: Monitors data from many collectors feed data in realtime into relational database Vary in number and location
Relational Database Supercomputer:
Analysis for data from relational database
Problem to solve
how can our system
operate continuously
allow for the dynamic addition and removal of both collectors and concentrators
with little impact on overall performance? .
Solutions: Juxtaposition
Data Collector Network
Jxta Benefits for P2P Network
Uniform decentralized addressing Easy addition and removal of new collectors
or concentratorsNetwork virtualization simplicity in design
Fault Resiliency continuous operations
Dynamic self-organized network maintenance-free operations
Support for a diversity of implementations hardward platforms, programming
languages, and communication protocols
Unique Identifier
Uniquely identify an entity and serves to locate it
No central name server like DNS Presented as URN
Sort of URI 64 bytes array
Typical id: urn:jxta:uuid 59616261646162…
C8168F0E4BDA903
Network Virtualization
Peer Endpoint Protocol
Used to dynamically find a route to send a message to another peer Uses queries send to other routers
Caches route information locally and uses remote peers Uses the relay service for peers that are not
reachable (firewall) Leasing mechanism
Uses the Endpoint service to send messages The PeerAdvertisement contains a list of
Transport Protocols Endpoint service used to delegate the sending
part to the appropriate protocol
End point protocols as drivers
Jxta routing example
Fault ResiliencyP2P network topology will change
unreliable nature of P2P peer
reroute message on the fly as peers come and
go in the network
peergroup level
support peergroup service -- redundantly
implemented services that should always be
available within a peergroup
Dynamic self-organized network
A peer with a uniform ID must Locate the local peers and discover their capabilitiesdiscover the peergroups that are available and join onediscover the services available in a peergroup and start using them
A peergroupserve as a network-partitioning mechanismensuring that advertisements are only related to he group membersalso serve authentication domain for certain applications
Weather station example
Concentrator - Jxta Services
Collector - Jxta clients
Concentrator Implementation
1. Read and process appropriate configuration file
2. Start Jxta
3. Join the group in the configuration file
4. Determine if the service ad is present. If not, create one and publish it.
5. Wait on pipe for message from collectors
6. Process the message and store in database
7. Go back to step 6
Collector Implementation1. Read and process appropriate configuration file2. Start Jxta3. Join the group specified in the configuration file4. Discover service ad by concentrator. If not, we
can not go ahead.5. Extract pipe information from service ad. 6. Collect data at timed intervals7. Create message containing the collector location
and data8. Send message to concentrator through pipe9. Go back to step 6
Application PatternTwo extremely loosely coupled populations Consumer and Producer
Consumer not willing to committed to one specific producerConsumer may want Select the best producers at any time Reduce dependence on one single producer Choose from one large dynamic community
whose size and topology is unmanageable