Objective What is RFT How does it work

Objective What is RFT ? How does it work Architecture of RFT and OGSA Issues Demo Questions

What is Reliability The ability of a system or component to perform its required functions under stated conditions for a specified period of time. (IEEE) What is Reliability in the context of File Transfer (What is the scope of the problem ) How much of it we want to address ? Reliability can mean different things to different people Hash out something that is most general and acceptable to wide range of applications.

Our Goal To design and implement a Service that allows byte streams to be transferred in a Reliable manner Reliability, in our context, means that problems of less than a certain, user defined magnitude are dealt with automatically. Build prototypes using different technologies. n n n Java Web Services Etc. .

Our Goal (cont. . ) A non user based service n n Grid. FTP already provides restart markers for recovery but however the client needs to be active. Loss of client requires a manual restart from scratch Store transfer state persistently Recover from a set of Failure conditions reliably

Failure Conditions List of Failure conditions we want to address n n n Network Failures like dropped connections Machine crashes Temporary Network outages Failure of File Systems Etc…

Interface submit. Transfer() n n Set of URLs File size for partial file transfers get. Status() cancel. Transfer() resume. Transfer()

State Diagram

Architecture

OGSA and RFT How does RFT fit in OGSA? Things that are different from SC Demo RFT is a Web Service Single Transfer Reliability Service Definition in WSDL Talks XML over SOAP just like any standard Web Service

RFT Web Service Interface submit. Transfer. Job() n n Intput message: from. URL and to. URL (strings) Output message: transfer. Job. ID (integer) commit. Transfer. Job() n n Input message: transfer. Job. ID Output message: transfer. Job. ID get. Status() n n Input message: transfer. Job. ID Output message: status (integer) get. Statistics() n n Input message: transfer. Job. Id Output message: Statistics ( complex type)

Our Experience SC 2001 Demo List of Tests n Longest – 3 days transferring 0. 3 Terabytes of data from ANL to NERSC Failures recovered from n n n NFS Failures Network outages Server crashes

Issues Language n n Prototypes are in Java Language issue should not matter since it is a service whose interface is a socket Persistence Mechanism n n We used Post. Gre. SQL as database to store the transfer state Can we use File based persistence mechanism Scalability n n Multiple instances of RFT which may appear as a single logical entity Request redirection ?

Issues (cont. . ) XRM Functionality n Reservations for disk and bandwidth Higher Level Services n n n Interaction between RFT and Higher level Services like Reliable Replication Service Scheduler ? ? Services like NWS that can give performance estimates Compute. Job Submission n File transfer as a Job ?

Issues(cont. . ) Security n n CAS Proxy renewal Error Propagation

DEMO SC 2001 Demo OGSA and RFT

More Info http: //www. mcs. anl. gov/~madduri/RFT. html

Questions ? ?