Race Condition Prevention for CASQL Database Management Systems
Students: Yiheng Wang and Dailin Liu
Summary: Nowadays, query intensive applications such as social network websites enhance the performance by extending the Relational Database Management System (RDBMS) with a middle-tier cache system. Write through a KVS can leverage main memory effectively and offer ACID consistency using an RDBMS at the same time. An example is Memcached in use by very large well know social network websites like Facebook, Twitter and Youtube. Unfortunately, such caches cannot maintain transactional consistency across the entire system, violating the isolation properties of the underlying database. Gumball Technique (GT) proposed by Shahram Ghandeharizadeh and Jason Yap  appears to be a good solution to race condition in Cache Augmented DBMSs(CADBMS), but leaves a key design challenge of when to delete the tombstones making deleted objects. In this paper, we implements Gumball Technique in a open-sourced KVS called Memcached, improves the performance by refining the strategy of managing "gumballs" in the cache system and further evaluates and compares the performance of the system under different workloads.
Analysis and Prediction of Transaction Latency in MySQL
Students: Zichao Fu, Liuyi Wang, and Sen Cai
Summary: In this project, we profiled a MySQL based OLTP system to investigate why different fraction of transactions affects the running latencies and which system calls result in these latency differences. We have conducted a series of experiments and gathered enough data to explore the problems. We found from our data that the percentage of transactions that involve heavy update operations is linearly correlated with the running time and the system calls which involve locking operation contribute most to the increasing running time when running multi-users rather than a single user in an OLTP system. We hope the results of our experiment can give future researchers help and hints to continue the research in analyzing OLTP transaction latencies.
Students: Matthew Kneiser, Vijairam Parasuraman, and Balaji Soundararajan