| 1. |
- Bogdanov, Kirill, et al.
(author)
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The Nearest Replica Can Be Farther Than You Think
- 2015
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In: Proceedings of the ACM Symposium on Cloud Computing 2015. - New York, NY, USA : Association for Computing Machinery (ACM). ; , s. 16-29
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Conference paper (peer-reviewed)abstract
- Modern distributed systems are geo-distributed for reasons of increased performance, reliability, and survivability. At the heart of many such systems, e.g., the widely used Cassandra and MongoDB data stores, is an algorithm for choosing a closest set of replicas to service a client request. Suboptimal replica choices due to dynamically changing network conditions result in reduced performance as a result of increased response latency. We present GeoPerf, a tool that tries to automate the process of systematically testing the performance of replica selection algorithms for geodistributed storage systems. Our key idea is to combine symbolic execution and lightweight modeling to generate a set of inputs that can expose weaknesses in replica selection. As part of our evaluation, we analyzed network round trip times between geographically distributed Amazon EC2 regions, and showed a significant number of daily changes in nearestK replica orders. We tested Cassandra and MongoDB using our tool, and found bugs in each of these systems. Finally, we use our collected Amazon EC2 latency traces to quantify the time lost due to these bugs. For example due to the bug in Cassandra, the median wasted time for 10% of all requests is above 50 ms.
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| 2. |
- Bogdanov, Kirill, et al.
(author)
-
Toward Automated Testing of Geo-Distributed Replica Selection Algorithms
- 2015
-
In: Proceedings of the 2015 ACM Conference on Special Interest Group on Data Communication. - New York, NY, USA : Association for Computing Machinery (ACM). ; , s. 89-90
-
Conference paper (peer-reviewed)abstract
- Many geo-distributed systems rely on a replica selection algorithms to communicate with the closest set of replicas. Unfortunately, the bursty nature of the Internet traffic and ever changing network conditions present a problem in identifying the best choices of replicas. Suboptimal replica choices result in increased response latency and reduced system performance. In this work we present GeoPerf, a tool that tries to automate testing of geo-distributed replica selection algorithms. We used GeoPerf to test Cassandra and MongoDB, two popular data stores, and found bugs in each of these systems.
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