54,040 research outputs found
A Peer-to-Peer Middleware Framework for Resilient Persistent Programming
The persistent programming systems of the 1980s offered a programming model
that integrated computation and long-term storage. In these systems, reliable
applications could be engineered without requiring the programmer to write
translation code to manage the transfer of data to and from non-volatile
storage. More importantly, it simplified the programmer's conceptual model of
an application, and avoided the many coherency problems that result from
multiple cached copies of the same information. Although technically
innovative, persistent languages were not widely adopted, perhaps due in part
to their closed-world model. Each persistent store was located on a single
host, and there were no flexible mechanisms for communication or transfer of
data between separate stores. Here we re-open the work on persistence and
combine it with modern peer-to-peer techniques in order to provide support for
orthogonal persistence in resilient and potentially long-running distributed
applications. Our vision is of an infrastructure within which an application
can be developed and distributed with minimal modification, whereupon the
application becomes resilient to certain failure modes. If a node, or the
connection to it, fails during execution of the application, the objects are
re-instantiated from distributed replicas, without their reference holders
being aware of the failure. Furthermore, we believe that this can be achieved
within a spectrum of application programmer intervention, ranging from minimal
to totally prescriptive, as desired. The same mechanisms encompass an
orthogonally persistent programming model. We outline our approach to
implementing this vision, and describe current progress.Comment: Submitted to EuroSys 200
S-Store: Streaming Meets Transaction Processing
Stream processing addresses the needs of real-time applications. Transaction
processing addresses the coordination and safety of short atomic computations.
Heretofore, these two modes of operation existed in separate, stove-piped
systems. In this work, we attempt to fuse the two computational paradigms in a
single system called S-Store. In this way, S-Store can simultaneously
accommodate OLTP and streaming applications. We present a simple transaction
model for streams that integrates seamlessly with a traditional OLTP system. We
chose to build S-Store as an extension of H-Store, an open-source, in-memory,
distributed OLTP database system. By implementing S-Store in this way, we can
make use of the transaction processing facilities that H-Store already
supports, and we can concentrate on the additional implementation features that
are needed to support streaming. Similar implementations could be done using
other main-memory OLTP platforms. We show that we can actually achieve higher
throughput for streaming workloads in S-Store than an equivalent deployment in
H-Store alone. We also show how this can be achieved within H-Store with the
addition of a modest amount of new functionality. Furthermore, we compare
S-Store to two state-of-the-art streaming systems, Spark Streaming and Storm,
and show how S-Store matches and sometimes exceeds their performance while
providing stronger transactional guarantees
Compensation methods to support cooperative applications: A case study in automated verification of schema requirements for an advanced transaction model
Compensation plays an important role in advanced transaction models, cooperative work and workflow systems. A schema designer is typically required to supply for each transaction another transaction to semantically undo the effects of . Little attention has been paid to the verification of the desirable properties of such operations, however. This paper demonstrates the use of a higher-order logic theorem prover for verifying that compensating transactions return a database to its original state. It is shown how an OODB schema is translated to the language of the theorem prover so that proofs can be performed on the compensating transactions
On fully superconducting rectifiers and fluxpumps. A review. Part 2: Commutation modes, characteristics and switches
This paper forms the second part of the review. Full and half wave superconducting transformer rectifiers are analysed. Modes of operation and loss mechanisms are detailed and a comparison between the behaviour of dynamos and rectifiers is presented. Investigations carried out to date still leave the flux pump relatively a long way from real applications. The possible use of a flux pump in a large magnet system and for the general protection of that system merits further study
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