Peergroups

1. Peergroups

2. Learning Objectives • This module will teach you how to manipulate groups • How to join a group • How to publish and discover groups • How to create a new group • How to create secure groups

3. Creating Peergroup ID • If you need to create a peergroup, all peers must use same peergroup ID • In general, use pre-defined string • Can use JXTA Shell to generate string: JXTA> mkpgrp mygroup JXTA> groupsgroup0: name = mygroup JXTA> cat group0...<GID>urn:jxta:uuid-71A8EC0B31BA471BB053B287211BC75602</GID>....

4. Publishing Peergroups • Peergroups are automatically published locally when they are created • Published with default expiration values • No need to explicitly call DiscoveryService.publish() • To remotely publish a peergroup • Call DiscoveryService.remotePublish

5. Joining Peergroups • Membership Service • Used to apply for peergroup membership, join a peergroup, and resign from a peergroup • Enables peer to establish an identity within a peergroup • Identities used by services to determine the capabilities which should be offered peers

6. Sequence of Establishing Identity • Apply • Peer provides membership service an initial credential; service returns an authenticator object • Join • The completed authenticator is returned to the membership service and the identity of the peer is adjusted • Resign • The existing identity for this peer is discarded

7. Secure Peergroups • Need to assign a secure membership service to the peergroup • Decentralized (Peergroup certificates) • Centralized (LDAP authentication server) • Define principal roles in the peergroup • Read only – read/write access • Act as relay or rendezvous • etc. • Peergroup advertisement publishing scope

8. Peergroup – Java API Creating & Publishing Peergroups getAllPurposePeerGroupImplAdvertisement() • Get an allPurpose peerGroup ModuleImplAdvertisement compatible with this group. newGroup(Advertisement pgAdv)newGroup(PeerGroupID pgID)newGroup(PeerGroupID gid, Advertisement impl, java.lang.String name, java.lang.String descr) • Create a new group and publish it. publishGroup(java.lang.String name, java.lang.String descr) • Force publication of the group if it hasn't already been done.

9. Membership Service – Java API Joining Peergroups apply(AuthenticationCredential application) • Request the necessary credential to join the group with which this service is associated. getAuthCredentials()getCurrentCredentials() • Returns the current credentials for this peer join(Authenticator authenticated) • Join the group by the virtue of the complete authentication provided. makeCredential(Element element) • Given a fragment of a StructuredDocument, reconstruct a Credential object from that fragment. resign() • Leave the group to which this service is attached.

10. Create a Peergroup— Java private PeerGroup createGroup() { PeerGroupAdvertisement adv; System.out.println("Creating a new group advertisement"); try { // create a new all purpose peergroup. ModuleImplAdvertisement implAdv = myGroup.getAllPurposePeerGroupImplAdvertisement(); PeerGroup pg = myGroup.newGroup(null, // Assign new group ID implAdv, // The implem. adv "PubTest", // Group name "testing group adv"); // Helpful descr. // print the name of the group and the peer group ID adv = pg.getPeerGroupAdvertisement(); PeerGroupID GID = adv.getPeerGroupID(); System.out.println(" Group = " +adv.getName() + "\n Group ID = " + GID.toString()); } catch (Exception e) { System.out.println("Group creation failed with " + e.toString()); return null; } try { // publish this advertisement (send to other peers, rdv peers) discovery.publish(adv, DiscoveryService.GROUP, PeerGroup.DEFAULT_LIFETIME, PeerGroup.DEFAULT_EXPIRATION); discovery.remotePublish(adv, DiscoveryService.GROUP); System.out.println("Group published successfully."); } catch (IOException e) { System.out.println("Error publishing group advertisement"); e.printStackTrace(); } return(pg); }

11. Join a Peergroup—Java private void joinGroup(PeerGroup grp) { StructuredDocument creds = null; try { // Generate the credentials for the Peer Group AuthenticationCredential authCred = new AuthenticationCredential( grp, null, creds ); // Get the MembershipService from the peer group MembershipService membership = grp.getMembershipService(); // Get the Authenticator from the Authentication creds Authenticator auth = membership.apply( authCred ); // All authenticators besides 'Null' require you to do something here. // Check if everything is okay to join the group if (auth.isReadyForJoin()){ Credential myCred = membership.join(auth); System.out.println("Joined group " + grp.getPeerGroupName()); // display the credential as a plain text document. System.out.println("\nCredential: "); StructuredTextDocument doc = (StructuredTextDocument) myCred.getDocument(new MimeMediaType("text/plain")); StringWriter out = new StringWriter(); doc.sendToWriter(out); System.out.println(out.toString()); out.close(); } else System.out.println("Failure: unable to join group"); } catch (Exception e){ System.out.println("Failure in authentication."); } }

12. Peergroup Service – C API Registering and Accessing Peergroups jxta_register_group_instance (Jxta_id *gid, Jxta_PG *pg) • This method registers a group instance. jxta_unregister_group_instance (Jxta_id *gid, Jxta_PG *pg) • This method unregisters a group instance. jxta_lookup_group_instance (Jxta_id *gid, Jxta_PG **pg) • This method is used to access a child peergroup instance jxta_PG_get_GID(Jxta_PG* self, Jxta_PGID** gid) • This method is used to access the peergroup ID jxta_PG_get_PID(Jxta_PG* self, Jxta_PID** pid) • This method is used to access peerid jxta_PG_get_groupname(Jxta_PG* self, JString** gname) • This method is used to access the peergroup name

13. Peergroup Service – C API Accessing Peergroup Services jxta_PG_get_endpoint_service(Jxta_PG* self,Jxta_endpoint_service** endp) • This method is used to access the peergroup endpoint service jxta_PG_get_rendezvous_service(Jxta_PG* self,Jxta_rdv_service** rdv) • This method is used to access the peergroup rendezvous service jxta_PG_get_discovery_service(Jxta_PG* self,Jxta_discovery_service** disco) • This method is used to access the peergroup discovery service jxta_PG_get__membership_service(Jxta_PG* self,Jxta_membership_service** membership) • This method is used to access the peergroup membership service jxta_PG_get_pipe_service(Jxta_PG* self, Jxta_pipe_service** pipe) • This method is used to access the peergroup pipe service jxta_PG_get_resolver_service(Jxta_PG* self, Jxta_resolver_service** resolver) • This method is used to access the peergroup resolver service jxta_PG_get_peerinfo_service(Jxta_PG* self, Jxta_peerinfo_service** peerinfo) • This method is used to access the peerinfo pipe service

14. Peergroup Service – C API Creating Peergroups jxta_PG_newfromadv (Jxta_PG *self, Jxta_advertisement *pgAdv Jxta_vector *resource_groups, Jxta_PG **result) • Instantiate a group from its given advertisement Use this when a published implementation advertisement for the group sub-class can be discovered. jxta_PG_newfromimpl (Jxta_PG *self, Jxta_PGID *gid, jxta_advertisement *impl, JString *name, JString *description, Jxta_vector *resource_groups, Jxta_PG **result) • Convenience method, instantiate a group from its elementary pieces and publish the corresponding peer group advertisement. jxta_PG_newfromid (Jxta_PG *self, Jxta_PGID *gid, Jxta_vector *resource_groups, Jxta_PG **result) • Instantiate a group from its group ID only.

15. Join a Group—C Jxta_PG * newPG = NULL; Jxta_PGA * pga = NULL /* Discover advertisement of the group we are looking to join */ jxta_PG_get_discovery_service(group, &discovery); discovery_service_get_local_advertisements(discovery, DISC_GROUP, (char *)jstring_get_string(attr), (char *)jstring_get_string(value), & res_vec); if (res_vec != NULL ) { for (i=0; i < jxta_vector_size(res_vec); i++ ){ jxta_vector_get_object_at (res_vec, (Jxta_object**)&pga, i); JXTA_OBJECT_SHARE(pga); } else { // No group advertisements retrieved } /* Reuse the resource groups of our parent. */ jxta_PG_get_resourcegroups( group, &resources ); /* add the new group's parent */ jxta_vector_add_object_last( resources, (Jxta_object*) group ); res = jxta_PG_newfromadv ( group, (Jxta_advertisement*) pga, resources, &newPG );

16. Join a Group—C (continued) if( res == JXTA_SUCCESS ) { // Group correctly joined } /* looking for a rendezvous */ jxta_PG_get_GID( newPG, &gid ); jxta_id_to_jstring( gid, &gidstr ); while( iterations < 20 ) { //Searching for Rendezvous /* flush */ if( 0 == (iterations % 3) ) { int qid = discovery_service_get_remote_advertisements(discovery, NULL, DISC_ADV, "RdvGroupId", jstring_get_string(gidstr), 5, NULL); } /* nap a while */ jpr_thread_delay( 5 * 1000 * 1000 );

17. Join a Group—C (continued) discovery_service_get_local_advertisements(discovery, DISC_ADV, "RdvGroupId", jstring_get_string(gidstr), & res_vec); if (res_vec != NULL ) { int i; for (i=0; i < jxta_vector_size(res_vec); i++ ) { Jxta_RdvAdvertisement * rdvAdv = NULL; jxta_vector_get_object_at ( res_vec, (Jxta_object**)&rdvAdv, i); if( NULL != rdvAdv ) jid = jxta_RdvAdvertisement_get_RdvPeerId( rdvAdv ); jxta_id_get_uniqueportion( jid, &jidstr ); addr_e = jxta_endpoint_address_new( (char*) jstring_get_string(jidstr)); jxta_PG_get_rendezvous_service( (Jxta_PG*) group, &rdv ); jxta_peer_set_address (peer, addr_e); jxta_rdv_service_add_peer( (Jxta_rdv_service*) rdv, peer); break; } } /* To resign from a peergroup */ Jxta_membership_service * membership; jxta_PG_get_membership_service( group, &membership ); if( NULL != membership ) { jxta_membership_service_resign( membership ); } }

18. End – Peergroups