Haren: A Framework for Ad-Hoc Thread Scheduling Policies for Data Streaming Applications

In modern Stream Processing Engines (SPEs), numerous diverse applications, which can differ in aspects such as cost, criticality or latency sensitivity, can co-exist in the same computing node. When these differences need to be considered to control the performance of each application, custom scheduling of operators to threads is of key importance (e.g., when a smart vehicle needs to ensure that safety-critical applications always have access to computational power, while other applications are given lower, variable priorities).Many solutions have been proposed regarding schedulers that allocate threads to operators to optimize specific metrics (e.g., latency) but there is still lack of a tool that allows arbitrarily complex scheduling strategies to be seamlessly plugged on top of an SPE. We propose Haren to fill this gap. More specifically, we (1) formalize the thread scheduling problem in stream processing in a general way, allowing to define ad-hoc scheduling policies, (2) identify the bottlenecks and the opportunities of scheduling in stream processing, (3) distill a compact interface to connect Haren with SPEs, enabling rapid testing of various scheduling policies, (4) illustrate the usability of the framework by integrating it into an actual SPE and (5) provide a thorough evaluation. As we show, Haren makes it is possible to adapt the use of computational resources over time to meet the goals of a variety of scheduling policies

ANAPSID: An Adaptive Query Processing Engine for SPARQL Endpoints

Abstract. Following the design rules of Linked Data, the number of available SPARQL endpoints that support remote query processing is quickly growing; however, because of the lack of adaptivity, query executions may frequently be unsuccessful. First, fixed plans identified following the traditional optimize-then-execute paradigm, may timeout as a consequence of endpoint availability. Sec-ond, because blocking operators are usually implemented, endpoint query en-gines are not able to incrementally produce results, and may become blocked if data sources stop sending data. We present ANAPSID, an adaptive query engine for SPARQL endpoints that adapts query execution schedulers to data availabil-ity and run-time conditions. ANAPSID provides physical SPARQL operators that detect when a source becomes blocked or data traffic is bursty, and opportunis-tically, the operators produce results as quickly as data arrives from the sources. Additionally, ANAPSID operators implement main memory replacement policies to move previously computed matches to secondary memory avoiding duplicates. We compared ANAPSID performance with respect to RDF stores and endpoints, and observed that ANAPSID speeds up execution time, in some cases, in more than one order of magnitude.

Vertical distribution of oribatid mites (acari: Oribatida) and some ecological parameters affecting the distribution pattern in south-west turkey

The vertical distribution of oribatid mites and its dependence on ecological parameters such as moisture, pH, temperature, soil pore size, and amount of organic matter was studied in five areas in the Dalaman province of Turkey. A total of 2,737 individuals was obtained, with 35.1% from litter, 24.7% from a depth of 0–5 cm, 26.1% from 5–10 cm, and 14.2% from 10–15 cm. Maximum density was found in litter, minimum density at a depth of 10–15 cm. It was found that the density of oribatid mites was most affected (at a statistically significant level) by soil pH, temperature, pore size and moisture. Soil pH has the highest influence on the number of mites in the soil (P<0.01), and may thus be used as an indicator for monitoring soil pollution and global heating. © 2006 Taylor & Francis Group, LLC

A new species and new distribution records of Zercon C. L. Koch from Iran (Acari: Zerconidae)

A new species of the family Zerconidae, Zercon persicus sp. n., is described based on female and male morphological characters. It was collected in West Azarbaijan province (northwestern Iran). Idiosomal chaetotaxy, poroidotaxy and related notations are illustrated. The similarities and differences between the related species within the genus are discussed. Records of some other Zercon species from the province are given for the first time. http://www.zoobank.org/urn:lsid:zoobank.org:pub:3D1122C7-2B86-40D2-974E-EE69035A2413. © 2018, © 2018 Taylor & Francis

Adaptive Query Processing: A Survey

In wide-area database systems, which may be running on unpredictable and volatile environments (such as computational grids), it is di#cult to produce e#cient database query plans based on information available solely at compile time. A solution to this problem is to exploit information that becomes available at query runtime and adapt the query plan to changing conditions during execution. This paper presents a survey on adaptive query processing techniques, examining the opportunities they o#er to modify a plan dynamically and classifying them into categories according to the problem they focus on, their objectives, the nature of feedback they collect from the environment, the frequency at which they can adapt, their implementation environment and which component is responsible for taking the adaptation decisions