Frequently Asked Questions

What are XtremWeb researches about ? What is XtremWeb ? What can I do with XtremWeb ? Top XtremWeb Research The aim of the project is to address several issues related to Global Computing and Peer-to-Peer systems: We are currently working on: Security of distributed resources (PC and Personal Devices), Result certification, Monitoring and availability prediction of remote resources, Light weight resources (Palm devices), Parallel application execution on Large Scale Distributed Systems (LSDS). XtremWeb is itself a Global Computing system but compared to the other systems it is designed to be very flexible and reconfigurable. So most of the server and worker subsystems are upgradable, dedicatable for any particular experiments. Global Computing and Peer-to-Peer systems raise a lot of issues. Here are some of them: Computing middleware, programming models, environments and toolkits; Processing algorithms for typical configurations involving; personal devices (large number of processors, limited bandwidth, frequent faults); Resource management, reservation and scheduling; Performance evaluation and modeling of systems consisting of personal devices; Benchmarking of peer-to-peer and client server computing/communication systems; Compute and I/O driven applications (scientific, engineering, and business); Integration of legacy applications with distributed computing systems that use personal devices; Services and economies of computational grids consisting of personal devices. If you are interested by research in the field of Global Computing and Peer-to-Peer systems, you may use XtremWeb as a software subtract to ease your design and experiments. Top Background XtremWeb is a research project belonging to light weight Grid systems. Its a Free Open Source and non-profit software platform to explore scientific issues and applications of Desktop Grid, Global Computing and Peer to Peer distributed systems. Like the other Distributed System Platforms, an XW platform uses a) remote resources (PCs, workstations, servers) connected to Internet or b) a pool of resources (PCs, workstations, servers) inside a LAN. Participants of an XW platform cooperate by providing their CPU idle time. The XtremWeb software platform allows to setup and run Distributed System projects. Such project must be based on a community of participants. For example, XtremWeb platforms allow a High School, a University, ... or a Company to setup and run a Global Computing or Peer to Peer distributed system for either a specific application or a range of applications. Here are the current installed platforms: XtremWeb (XW) is a software platform designed to serve as a substrate for Global Computing (Large Scale Distributed System) experiments. XtremWeb belongs to the so called Cycle Stealing Environment family. Like some other projects XtremWeb extends the principle of cycle stealing to the PC connected to Internet. XtremWeb is composed of Client, Servers and Workers. XtremWeb can be used to build a Global Computing System with centralized control, job scheduling and result collection: This architecture corresponds to most of well known Global Computing Projects. Compared to some other platforms, XtremWeb also allows to connect several Servers and Result Collector on a single project (Workers keep a collection of Server and Result collectors IP address). During the execution, the workers contact the Server to get jobs. In response, the Server send a set of parameter and it also may send an application if the application is not already stored in the Workers. When the Workers end their job, they contact the Result collector to send the results. Depending on the result size, the communication between the Workers and the Result collector use different protocols. Currently, the worker may send result size up to 100 MBytes. In this architecture, the Client and the Server are the same computer. XtremWeb can also be used to build centralized Peer-to-Peer Systems such as some well known projects related to audio file exchange. However, currently, XtremWeb doesn't allow to store data on the Client/Worker resources. XtremWeb only allows P2P computing using the following design: Typically, one or several applications are downloaded on the Workers. Any Worker may submit jobs by contacting the P2P Server. In this case, the Worker behaves as a Client. Jobs submitted by Client are registered on the Server and scheduled on Workers. In this architecture any Worker can be a Client. Currently we recommend to use only trusted applications with this architecture. The next release of XW will encompass a sandboxing mechanism to protect the Worker of hackers attack. With this mechanism, any program may be submitted to the system and ran on a protected Worker. Note that the XtremWeb is not limited to centralized architectures and we are currently extending it to a hierarchical design. Also, Workers may send their results directly to Clients to limit the bandwidth consummation. Top What can I do with XtremWeb? As a system software, XtremWeb allows you to: use a Peer-to-Peer computing platform such as P2P Povray, participate (provide CPU cycles) to a Global Computing or a Peer-to-Peer Project by joining an XtremWeb platform (see the projects links on the main page), be collaborator of XtremWeb by helping us developing XtremWeb, easily build your own General Purpose Global Computing System. Users may submit jobs just by visiting the job submission page of a Peer-to-Peer computing project such as P2P PovRay. Participants may download the Worker software to participate. XtremWeb Worker examines constantly the workload of your PC. When the workload becomes insignificant, your PC starts participating to a world wide experiment (research or large contests). For most of the PCs, the computation is done during the night. Collaborators may download the entire software (Worker, Server, Lan administrator) to setup their own XtremWeb platform. See MyXtremWeb program. Large institutions that are spread among several geographical sites and that are using cycle stealing to increase their computational power may use XtremWeb to manage all the resources through a single environment. By downloading the entire XtremWeb system you will be able to launch a Global Computing or a Peer-to-Peer Computing system. To do so, you will have to setup a community of workers. Dedicated Global Computing System particularly match the requirements of institutions like Schools, Universities, Laboratories, Libraries, Factories, Industries, ..., Companies that need a system allowing the use of idle resources during the nights or week-end. Top Top Installation SQL server access error The installation may fail due to an SQL access error complaining that server is not reachable. The error message ends with something like : SQL server not running ? This is certainly due to your SQL server configuration. Please check that your SQL config file has the following line commented : skip-networking So that network connection is allowed through the port. Top XtremWeb server seems not reachable The server is not reachable, even if you start a worker in the same machine ; the worker throws an Exception complaining about RMI connections fails. Please ensure your /etc/hosts file looks like this : 127.0.0.1 localhost 1.2.3.4 yourHostName The localhost line should definitly not contain your host name (don't ask why...). The following makes RMI connections impossible : 127.0.0.1 yourHostName localhost 1.2.3.4 yourHostName Top Error messages when lauching the server The following message may appear when launching the server, either by rc.xtremweb.server or by xtremweb.server Warning: bad syntax, perhaps a bogus '-'? See http://procps.sf.net/faq.html This is linux version dependant and has no effect :) Top The server crashes immediatly The server initialization may fail at boot time, complaining about some stub classes not known. If so, please insure there is no rmiregistry running before starting the server as the script try to start its own rmiregistry.