Quaestor: Query web caching for database-as-a-service providers

Today, web performance is primarily governed by round-trip latencies between end devices and cloud services. To improve performance, services need to minimize the delay of accessing data. In this paper, we propose a novel approach to low latency that relies on existing content delivery and web caching infrastructure. The main idea is to enable application-independent caching of query results and records with tunable consistency guarantees, in particular bounded staleness. Q uaestor (Query Store) employs two key concepts to incorporate both expiration-based and invalidation-based web caches: (1) an Expiring Bloom Filter data structure to indicate potentially stale data, and (2) statistically derived cache expiration times to maximize cache hit rates. Through a distributed query invalidation pipeline, changes to cached query results are detected in real-time. The proposed caching algorithms offer a new means for data-centric cloud services to trade latency against staleness bounds, e.g. in a database-as-a-service. Q uaestor is the core technology of the backend-as-a-service platform Baqend, a cloud service for low-latency websites. We provide empirical evidence for Q uaestor 's scalability and performance through both simulation and experiments. The results indicate that for read-heavy workloads, up to tenfold speed-ups can be achieved through Q uaestor 's caching. </jats:p

A trigger-based middleware cache for ORMs

ACM/IFIP/USENIX 12th International Middleware Conference, Lisbon, Portugal, December 12-16, 2011. ProceedingsCaching is an important technique in scaling storage for high-traffic web applications. Usually, building caching mechanisms involves significant effort from the application developer to maintain and invalidate data in the cache. In this work we present CacheGenie, a caching middleware which makes it easy for web application developers to use caching mechanisms in their applications. CacheGenie provides high-level caching abstractions for common query patterns in web applications based on Object-RelationalMapping (ORM) frameworks. Using these abstractions, the developer does not have to worry about managing the cache (e.g., insertion and deletion) or maintaining consistency (e.g., invalidation or updates) when writing application code. We design and implement CacheGenie in the popular Django web application framework, with PostgreSQL as the database backend and memcached as the caching layer. To automatically invalidate or update cached data, we use triggers inside the database. CacheGenie requires no modifications to PostgreSQL or memcached. To evaluate our prototype, we port several Pinax web applications to use our caching abstractions. Our results show that it takes little effort for application developers to use CacheGenie, and that CacheGenie improves throughput by 2-2.5× for read-mostly workloads in Pinax.Quanta Computer (Firm

Providing caching abstractions for web applications

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 99-101).Web-based applications are used by millions of users daily, and as a result a key challenge facing web application designers is scaling their applications to handle this load. A crucial component of this challenge is scaling the data storage layer, especially for the newer class of social networking applications that have huge amounts of shared data. Caching is an important scaling technique and is a critical part of the storage layer for such high-traffic web applications. Usually, building caching mechanisms involves significant effort from the application developer to maintain and invalidate data in the cache. In this work we present CacheGenie, a system which aims to make it easy for web application developers to build caching mechanisms in their applications. It achieves this by proposing high-level caching abstractions for frequently observed query patterns in web applications. These abstractions take the form of declarative query objects, and once the developer defines them, she does not have to worry about managing the cache (i.e., insertion and deletion) or maintaining consistency (e.g., invalidation or updates) when writing application code. We designed and implemented CacheGenie in the popular Django web application framework, with PostgreSQL as the database backend and memcached as the caching layer. We use triggers inside the database to automatically invalidate or keep the cache synchronized, as desired by the developer. We have not made any modifications to PostgreSQL or memcached. To evaluate our prototype, we ported several Pinax web applications to use our caching abstractions and performed several experiments. Our results show that it takes little effort for application developers to use CacheGenie, and that caching provides a throughput improvement by a factor of 2-2.5 for read-mostly workloads.by Priya Gupta.S.M

An architecture for recycling intermediates in a column-store

Automatically recycling (intermediate) results is a grand challenge for state-of-the-art databases to improve both query response time and throughput. Tuples are loaded and streamed through a tuple-at-a-time processing pipeline avoiding materialization of intermediates as much as possible. This limits the opportunities for reuse of overlapping computations to DBA-defined materialized views and function/result cache tuning. In contrast, the operator-at-a-time execution paradigm produces fully materialized results in each step of the query plan. To avoid resource contention, these intermediates are evicted as soon as possible. In this paper we study an architecture that harvests the by-products of the operator-at-a-time paradigm in a column store system using a lightweight mechanism, the recycler. The key challenge then becomes selection of the policies to admit intermediates to the resource pool, their retention period, and the eviction strategy when facing resource limitations. The proposed recycling architecture has been implemented in an open-source system. An experimental analysis against the TPC-H ad-hoc decision support benchmark and a complex, real-world application (SkyServer) demonstrates its effectiveness in terms of self-organizing behavior and its significant performance gains. The results indicate the potentials of recycling intermediates and charters a route for further development of database kernels

An architecture for recycling intermediates in a column-store

Automatic recycling intermediate results to improve both query response time and throughput is a grand c

A BitTorrent-based peer-to-peer database server

Database systems have traditionally used a Client-Server architecture, where clients send queries to a database server. If the data proves popular, the server may become overloaded, leading to clients experiencing an increase in query response time. In the domain of file-sharing, the problem of server overloading has been successfully addressed by the use of Peer-to-Peer (P2P) techniques in which users (peers) supply files – or pieces of files – to each other. This thesis will examine whether P2P techniques can be applied successfully in a database environment. It will introduce the Wigan Peer-to-Peer Database System, a P2P database system based on the popular BitTorrent file-sharing protocol. The potential benefits of a P2P database system include performance and scalability; allowing peers to answer each others’ queries will reduce the load on the database server and so could overcome the problem of a busy server becoming overloaded. Other potential benefits are fault tolerance and cost reduction. The Wigan architecture is introduced in this thesis, firstly by describing the BitTorrent algorithms and then by discussing how these algorithms must be modified for use in a database system. Experiments carried out on a simulator of Wigan are analysed in order to determine factors which affect its performance. These allow the identification of scenarios where Wigan could outperform a traditional database server. Further extensions to the Wigan architecture are discussed in this thesis, including possible means of handling data updates.EThOS - Electronic Theses Online ServiceGBUnited Kingdo