A Cloud Filesystem With Locking Service

Yijie Ma

Carnegie Mellon University

ABSTRACT

The consistency of sharing file is always a concern when the file is
written or read by multiple clients at the same time. If a locking
mechanism is not used, then the last-writer-win situation may occur so
that the previous writing will be lost. Systems that cannot withstand
this situation such as an online banking system needs a locking
service to keep track of all operations on shared resource, keep them
in order and do not miss one of them. The author of this paper tries
to solve this problem under the situation when a single datastore is
shared by multiple clients. The system developed by the author is a
cloud filesystem using Amazon S3 as datastore and a locking server
which uses reader-writer lock to maintain the consistency of the file
on S3. The first part of this paper presents the detail of the system
architecture.  The second part presents design of different parts and
two reader-writer lock algorithms and compare them in terms of wakeup
latency and writer starvation issues.