Adaptive TTL-Based Caching for Content Delivery
Adaptive TTL-Based Caching for Content Delivery
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DOI：
10.1145/3078505.3078560
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发表时间：
2017-04
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通讯作者：
S. Basu;Aditya Sundarrajan;Javad Ghaderi;S. Shakkottai;R. Sitaraman
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作者：
S. Basu;Aditya Sundarrajan;Javad Ghaderi;S. Shakkottai;R. Sitaraman
内容交付网络（CDN）缓存并提供互联网上大部分用户请求的内容，包括网页、视频和软件下载。我们提出了两个基于TTL的缓存算法，自动适应现实世界的内容请求的异构性，突发性和非平稳性。第一个算法称为d-TTL动态适应TTL参数使用随机逼近方法，并实现了一个给定的可行的目标命中率。第二种算法称为f-TTL，它使用两个缓存，每个缓存都有自己的TTL。较低级别的缓存自适应地过滤掉非静态内容，而较高级别的缓存存储频繁访问的静态内容。我们实现了d-TTL和f-TTL，并使用来自生产CDN服务器的超过5亿个请求的广泛的九天跟踪来评估这两种算法。我们表明，d-TTL和f-TTL收敛到他们的命中率目标的误差约为1.3%。我们还表明，f-TTL需要一个显着较小的缓存大小比d-TTL实现相同的命中率，因为它有效地过滤掉很少访问的内容。
Content Delivery Networks (CDNs) cache and serve a majority of the user-requested content on the Internet, including web pages, videos, and software downloads. We propose two TTL-based caching algorithms that automatically adapt to the heterogeneity, burstiness, and non-stationary nature of real-world content requests. The first algorithm called d-TTL dynamically adapts a TTL parameter using a stochastic approximation approach and achieves a given feasible target hit rate. The second algorithm called f-TTL uses two caches, each with its own TTL. The lower-level cache adaptively filters out non-stationary content, while the higher-level cache stores frequently-accessed stationary content. We implement d-TTL and f-TTL and evaluate both algorithms using an extensive nine-day trace consisting of more than 500 million requests from a production CDN server. We show that both d-TTL and f-TTL converge to their hit rate targets with an error of about 1.3%. We also show that f-TTL requires a significantly smaller cache size than d-TTL to achieve the same hit rate, since it effectively filters out rarely-accessed content.