Skewed write-intensive key-value storage workloads are increasingly observed in modern data centers, yet they also incur server overloads due to load imbalance. Programmable switches provide viable solutions for realizing load-balanced caching on the I/O path, and hence implementing write-back caching in programmable switches is a natural approach to absorb frequent writes and improve write performance. However, enabling in-switch write-back caching is challenged by not only the strict programming rules and limited stateful memory of programmable switches, but also the need for reliable protection against data loss due to switch failures. We first propose FarReach, a new caching framework that supports fast, available, and reliable in-switch write-back caching. FarReach carefully co-designs both the control and data planes for cache management in programmable switches, so as to achieve high data-plane performance with lightweight control-plane management. We further extend FarReach into DistReach, which reduces the reliability maintenance overhead via distributed switch deployment. Our experimental results on a Tofino-switch testbed show that FarReach achieves a throughput gain of up to$6.6\times $over a state-of-the-art in-switch caching approach under skewed write-intensive workloads. Also, DistReach reduces the crash recovery time of FarReach by 77.4%.

In-band network telemetry (INT) enriches network management at scale through the embedding of complete device-internal states into each packet along its forwarding path, yet such embedding of INT information also incurs significant bandwidth overhead in the data plane. We propose DeltaINT, a general INT framework that achieves extremely low bandwidth overhead and supports various packet-level and flow-level applications in network management. DeltaINTbuilds on the insight that state changes are often negligible at most time, so it embeds the complete state information into a packet only when the state change is deemed significant. We propose two variants for DeltaINTthat trade between bandwidth usage and measurement accuracy, while both variants achieve significantly lower bandwidth overhead than the original INT framework. We theoretically derive the time/space complexities and the guarantees of bandwidth mitigation for DeltaINT. We implement DeltaINTin both software and P4. Our evaluation shows that DeltaINTsignificantly mitigates the bandwidth overhead, and the deployment in a Tofino switch incurs limited hardware resource usage.

In-band network telemetry (INT) enriches network management at scale through the embedding of complete device-internal states into each packet along its forwarding path, yet such embedding of INT information also incurs significant band-width overhead in the data plane. We propose DeltaINT, a general INT framework that achieves extremely low bandwidth overhead and supports various packet-level and flow-level applications in network management. DeltaINT builds on the insight that state changes are often negligible at most time, so it embeds a state into a packet only when the state change is deemed significant. We theoretically derive the time/space complexities and the bounds of bandwidth mitigation for DeltaINT. We implement DeltaINT in both software and P4. Our evaluation shows that DeltaINT reduces up to 93% of INT bandwidth, and its deployment in a Barefoot Tofino switch incurs limited hardware resource usage.

Computing per-key aggregation is indispensable in streaming data analysis formulated as two phases, an update phase and a recovery phase. As the size and speed of data streams rise, accurate per-key information is useful in many applications like anomaly detection, attack prevention, and online diagnosis. Even though many algorithms have been proposed for per-key aggregation in stream processing, their accuracy guarantees only cover a small portion of keys. In this paper, we aim to achieve nearly full accuracy with limited resource usage. We follow the line of sketch-based techniques. We observe that existing methods suffer from high errors for most keys. The reason is that they track keys by complicated mechanism in the update phase and simply calculate per-key aggregation from some specific counter in the recovery phase. Therefore, we present PR-Sketch, a novel sketching design to address the two limitations. PR-Sketch builds linear equations between counter values and per-key aggregations to improve accuracy, and records keys in the recovery phase to reduce resource usage in the update phase. We also provide an extension called fast PR-Sketch to improve processing rate further. We derive space complexity, time complexity, and guaranteed error probability for both PR-Sketch and fast PR-Sketch. We conduct trace-driven experiments under 100K keys and 1M items to compare our algorithms with multiple state-of-the-art methods. Results demonstrate the resource efficiency and nearly full accuracy of our algorithms.

Database management systems (DBMSs) have a plethora of tunable knobs that control almost everything in the system. The performance of a DBMS is highly dependent on these configuration knobs, however, getting this tuning right is hard. Many organizations resort to hiring experts to configure these knobs, but this is prohibitively expensive. As databases grow in both size and complexity, optimizing a DBMS has surpassed the abilities of even the best human experts. We recently introduced OtterTune, a tuning service that is able to automatically find good settings for a DBMS's configuration knobs. OtterTune leverages data collected from previous tuning efforts to train machine learning models, and recommends new configurations that are as good as or better than ones generated by existing tools or a human expert. In this demonstration, we showcase OtterTune's ability to automatically select a configuration that improves a DBMS's performance.