AdaptCache: Adaptive Data Partitioning and Migration for Distributed Object Caches

Caching is an important aspect of today's web enterprise systems, enhancing performance and reducing access frequency to the backend storage server. However, when implemented as an independent component, such as when using Memcached, access to the remote cache can lead to considerable overhead and delay. Instead, in this paper we propose a cooperative and integrated cache framework where each application server has its own local cache but can also access the caches of other servers. Our solution dynamically distributes objects across caches and requests across servers such that the load is equally distributed across servers and servers find the objects they need for request execution in their local cache most of the time. The challenge is to handle the complex workloads of current e-commerce sites where requests can access more than one object and change the object set they access over time, and different request types access overlapping sets of objects. As such, we look at a whole range of distribution mechanisms and analyze their behavior in detail. We evaluated the various alternatives using the YCSB and RUBiS benchmarks, showing that our approach is applicable in different dynamic workload scenarios and is able to autonomously capture workload changes and adapt instantly.