TRAGEN: a synthetic trace generator for realistic cache simulations

Anirudh Sabnis, Ramesh K. Sitaraman

Abstract: Traces from production caching systems of users accessing content are seldom made available to the public as they are considered private and proprietary. The dearth of realistic trace data makes it difficult for system designers and researchers to test and validate new caching algorithms and architectures. To address this key problem, we present TRAGEN, a tool that can generate a synthetic trace that is "similar" to an original trace from the production system in the sense that the two traces would result in similar hit rates in a cache simulation. We validate TRAGEN by first proving that the synthetic trace is similar to the original trace for caches of arbitrary size when the Least-Recently-Used (LRU) policy is used. Next, we empirically validate the similarity of the synthetic trace and original trace for caches that use a broad set of commonly-used caching policies that include LRU, SLRU, FIFO, RANDOM, MARKERS, CLOCK and PLRU. For our empirical validation, we use original request traces drawn from four different traffic classes from the world's largest CDN, each trace consisting of hundreds of millions of requests for tens of millions of objects. TRAGEN is publicly available and can be used to generate synthetic traces that are similar to actual production traces for a number of traffic classes such as videos, social media, web, and software downloads. Since the synthetic traces are similar to the original production ones, cache simulations performed using the synthetic traces will yield similar results to what might be attained in a production setting, making TRAGEN a key tool for cache system developers and researchers.