0. Tycho: A Resource Discovery and Messaging Framework for Distributed Applications
Matthew Grove Cluster 2006

1. Outline Introduction and motivation, The architecture of Tycho,
Implementation details,
Updated benchmarking results,
Content distribution (Tycho swarm utility),
Summary.

2. Introduction
Tycho is a reference implementation of a combined extensible wide-area messaging framework with a built in distributed registry:
The Tycho components are:
Mediators,
Clients (Producers and Consumers).
Tycho provides services to allow clients to discover each other using a Virtual Registry (VR) made up of a network of mediators – this also aids communication over both LAN and WAN.
Tycho aims to simplify and speed application development by freeing developers from the need to use combinations of software to provide discovery and messaging services.

3. Tycho’s Architecture

4. General Design Philosophy
Reuse existing software components, if possible, rather than reinvent services or functionality.
Try to make use of existing software infrastructure.
Make Tycho simple to install, configure and use.
Provide a ‘basic release’ with the ability to extend functionality with a further more sophisticated component (Tycho utilities).
Java was used for portability and interoperability with other distributed systems, plus rapid development.

5. The Two Parts of Tycho Messaging: Virtual Registry:
Secure asynchronous communications between Consumers, Producers and Mediators.
Virtual Registry:
Boot-strapping – allows mediators to discover each other and form the VR with minimal hardwiring.
Communications - secure routing of queries between Virtual Registries.
Caching: keep a temporary local copy of some information to reduce the amount of communications between peers.

6. Tycho Mediator Implementation
Tycho provides a choice of implementations for each core service.

7. Tycho Clients & Utilities
The Tycho Connector provides the API for building producers and consumers.
Extra functionality can be added as utilities.

8. Tycho Core Services
Transport handler, allows different protocols to be used for communications (HTTP(S), Sockets, IRC).
Local store, for a mediator and VR information (JDBC, Java simple store).
Boot service, used by the VR within a mediator to locate and join the rest of the VR (HTTP(S), IRC).
Query parser and result annotator, to support different query and markup languages (SQL, LDIF).
Web wasn’t around until DNS was also done in 1988

9. Example Tycho Setup

10. Tycho Benchmarks Three rounds of benchmarking were performed:
Communications (A) - measured the performance of inter-client and inter-mediator messaging for Tycho and NaradaBrokering.
Virtual Registry tests (B) - measured and compared the performance of the Tycho VR to MDS4 and R-GMA.
Component Tests (C) - different components of the VR were tested in various configurations – these tests are discussed elsewhere.

11. Communications - Latency
The latency of communication for LAN and simulated WAN messaging was measured.
The tests used two clients with varying message size (ping-pong tests).
An eight node cluster was used to run the tests.

12. Communication Tests - Summary
Tycho has a lower latency and higher bandwidth than NaradaBrokering in all the tests.
With respect to scalability of producers and consumers, when either systems is saturated, the performance is stable under heavy load, however:
NaradaBrokering needs the JVM heap size to be increased as the number of clients increases (due to internal buffers):
Tycho used the default heap for all of the tests.

13. Virtual Registry Tests (B)
Two tests were used to measure aspects of the performance of Tycho’s VR, MDS4 and R-GMA:
Number of records in a registry (100,000 records),
Number of simultaneous client queries (1000 clients).
The tests were repeated with two different queries:
(S1) a single random record was selected,
(S2) all of the records were selected (worst case scenario).
Setup for comparison tests is in slide 16

14. VR Tests - Records (S1)
MDS4 out of memory

15. VR Tests - Records (S2)
MDS4 out of memory

16. VR Tests - Clients (S1)
R-GMA out of memory

17. Summary of VR Tests
Tycho has a better performance and client-scalability than both R-GMA and MDS4.
The heap R-GMA and MDS4 has to be set to 1.5 Gbytes (the max we could set) to carry out the tests.
Memory management in Java is an issue:
Without limited buffering or flow control, consuming the Java heap is a problem.
Storing information internally using XML seems to be a source for some of these memory problems:
Java database solutions such as HSQDLB can provide a high-performance solution for off-loading some of the storage requirements to disk.

18. Tycho Core – Future Work
Some performance improvements:
Caching of local mediator queries to reduce response times,
Use of a hybrid VR-interconnect to use IRC for query routing and HTTP for transporting large responses.
Additional functionality can be added to provide advanced services:
WS-based transport handlers for interoperability.

19. Tycho Applications
We developed a number of applications to further validate the implementation.
These include:
Demonstrations of publishing and discovering distributed webcams,
Remote resource discovery for the VOTechBroker project,
Part of the European Virtual Observatory project, Tycho provides automatic resource discovery for job submission.
Binding components for the Semantic Log Analyser (Slogger) project together:
Here Tycho helps locate and gather distributed logs for analysis.

20. The Tycho Swarm Utility
The swarm utility is a tool for distributed content distribution.
The utility was developed to test the potential of Tycho utilities and also further stress test the overall infrastructure:
By simultaneously utilising the VR and messaging functions,
Storing and updating thousands of entries records in the VR,
Sending thousands of multi-megabyte messages between clients.
Its potential uses include:
Distributing files for collaboration purposes,
Staging data for computation,
Mirroring and managing large data sets.

21. Swarm Utility Overview
The swarm utility provides distributed content distribution similar to BitTorrent.
Content is split into ‘chunks’ and the VR is used to store chunk availability.
Peers use the VR to locate each other and decide what chunks to download.
Tycho messages are used to transfer the chunks between peers and peers cooperate to distribute the content throughout the swarm.

22. Swarm Utility Architecture

23. Summary
The initial reference implementation of Tycho has been completed.
It can be downloaded from:
Both the messaging code and VR have been benchmarked and perform well.
The focus now is on developing Tycho utilities to provide more feature rich functionally.

24. Webcam Browser Demo

25. Links Project Web page: The DSG Web page: The ACET Web page:
The DSG Web page:
The ACET Web page: