Speaker
Dr
Steve Fisher
(RAL)
Description
R-GMA, as deployed by LCG, is a large distributed system. We are
currently addressing some design issues to make it highly reliable,
and fault tolerant.
In validating the new design, there were two classes of problems to
consider: one related to the flow of data and the other to the loss of
control messages. R-GMA streams data from one place to another; there
is a need to consider the behaviour when data is being inserted more
rapidly into the system than taken out and more generally how to deal
with bottlenecks. In the original R-GMA design the system tried hard
to deliver all control messages; those messages that were not
delivered quickly were queued for retry later. In the case of badly
configured firewalls, network problems or very slow machines this led
to long queues of messages, some of which were superseded by later
messages that were also queued. In the new design no individual
control message is critical; the system just needs to know if each
message was received successfully.
The system should also avoid single points of failure. However this
can require complex code resulting in a system that is actually less
reliable.
We describe how we have dealt with bottlenecks in the flow of data,
loss of control messages and the elimination of single points of
failure to produce a robust R-GMA design. The work presented, though
in the context of R-GMA, is applicable to any large distributed
system.
Primary authors
Mr
A Paventhan
(RAL)
Mr
Adebiyi Kuseju
(RAL)
Mr
Alastair Duncan
(RAL)
Dr
Antony Wilson
(RAL)
Mr
Ming Jiang
(RAL)
Ms
Parminder Bhatti
(RAL)
Dr
Steve Fisher
(RAL)
