This document discusses using XMPP (eXtensible Messaging and Presence Protocol) for asynchronous messaging in an Eclipse client-server architecture. It defines XMPP, describes its architecture of clients connecting to local servers which then connect to other servers, and provides examples of how it can be used for long-running tasks, optimistic locking, and floating licenses.

1. An eclipse client server architecture
with asynchronous messaging
based on XMPP
Thomas Kratz
EclipseCon Europe 2011

2. What is XMPP?
• eXtensible Messaging and Presence Protocol
• Bi-directional streaming XML
• Core: IETF RFC 3920, 3921
• Extensions: XMPP Standards Foundation (XSF)
– Membership-based
– Elected technical council
– Unit of work: XMPP Extension Protocol (XEP)
– Process: Experimental, Proposed, Draft, Final
• Goals:
– Simple clients
– Federate everything

3. XMPP Architecture
• Addressing Scheme: node@domain/resource
– JID = Jabber ID
– Node: identity, e.g. user name
– Domain: DNS domain name
– Resource: device identifier
– node@domain identifies a person
• Client talks to “local” server
– Wherever the user account is hosted
– Tied to directory if desired
– Organizational policy enforced
• Servers talk to other servers
– DNS lookup on domain portion of address
– Dialback, MTLS for security
– One connection for many conversations

4. The Mango stack
Client
Synchronous remote Asynchronous
service calls notifications
through Spring‘s through Smack
HttpInvoker XMPP Api
Server

5. Long running tasks
• http-service call spawns a worker thread on
the server and returns immediately
• Client UI runs a fake worker job (Eclipse Jobs
API) that listens to XMPP messages
• Worker Thread reports progress to client Job
through XMPP messages
• Client Job fetches result through second http-
service call

6. Not so optimistic
locking
• Eclipse Editor lifecycle sends XMPP messages
on open/save/close
• Server keeps track of opened database
entities
• Sends warning on possible conflict
• If an enitity gets changed, other users get
notified to reload their editor input to prevent
conflicts.

7. Floating Licene
• Server listens to the „Presence“ part of the
XMPP protocol
• Keeps track of online users
• Rejects login if maximum user count is
exceeded
• Notifies online users before server shutdown
to prevent data loss.

8. Q&A
• Thank you for listening!
• Reach me at eiswind@googlemail.com