Federated computing, including federated learning and federated analytics, needs to meet certain task Service Level Objective (SLO) in terms of various performance metrics, e.g., mean task response time and task tail latency. The lack of control and access to client activities requires a carefully crafted client selection process for each round of task processing to meet a designated task SLO. To achieve this, one must be able to predict task performance metrics for a given client selection per round of task execution. In this paper, we develop, FedSLO, a general framework that allows task performance in terms of a wide range of performance metrics of practical interest to be predicted for synchronous federated computing systems, in line with the Google federated learning system architecture. Specifically, with each task performance metric expressed as a cost function of the task response time, a relationship between the task performance measure - the mean cost and task/subtask response time distributions is established, allowing for unified task performance prediction algorithms to be developed. Practical issues concerning the computational complexity, measurement cost and implementation of FedSLO are also addressed. Finally, we propose preliminary ideas on how to apply FedSLO to the client selection process to enable task SLO guarantee.

Unexpected long query latency of a database system can cause domino effects on all the upstream services and severely degrade end users' experience with unpredicted long waits, resulting in an increasing number of users disengaged with the services and thus leading to a high user disengagement ratio (UDR). A high UDR usually translates to reduced revenue for service providers. This paper proposes UTSLO, a UDR-oriented SLO guaranteed system, which enables a database system to support multi-tenant UDR targets in a cost-effective fashion through UDR-oriented capacity planning and dynamic UDR target enforcement. The former aims to estimate the feasibility of UDR targets while the latter dynamically tracks and regulates per-connection query latency distribution needed for accurate UDR target guarantee. In UTSLO, the database service capacity can be fully exploited to efficiently accommodate tenants while minimizing resources required for UDR target guarantee.

A primary design objective for Data-intensive User-facing (DU) services for cloud and edge computing is to maximize query throughput, while meeting query tail latency Service Level Objectives (SLOs) for individual queries. Unfortunately, the existing solutions fall short of achieving this design objective, which we argue, is largely attributed to the fact that they fail to take the query fanout explicitly into account. In this paper, we propose TailGuard based on a Tail-latency-SLO-and-Fanout-aware Earliest-Deadline-First Queuing policy (TF-EDFQ) for task queuing at individual task servers the query tasks are fanned out to. With the task queuing deadline for each task being derived based on both query tail latency SLO and query fanout, TailGuard takes an important first step towards achieving the design objective. TailGuard is evaluated against First-In-First-Out (FIFO) task queuing, task PRIority Queuing (PRIQ) and Tail-latency-SLO-aware EDFQ (T-EDFQ) policies by simulation. It is driven by three types of applications in the Tailbench benchmark suite. The results demonstrate that TailGuard can improve resource utilization by up to 80%, while meeting the targeted tail latency SLOs, as compared with the other three policies. TailGuard is also implemented and tested in a highly heterogeneous Sensing-as-a-Service (SaS) testbed for a data sensing service, with test results in line with the other ones.

The Fork-Join structure underlays many distributed computing applications in data centers. In this paper, we develop a technique, called ForkMV, to estimate the mean and variance of request response time for Fork-Join queuing networks (FJQNs) with both short-tailed and long-tailed service time distributions and arbitrary request fanout degrees (i.e., the number of Fork nodes). Specifically, for an FJQN with any given service time distribution of practical interests, ForkMV is able to estimate the mean and variance of request response time, accurate enough to facilitate effective resource allocation for data center applications. The test results indicate that in the entire range of the fanout degrees being tested (i.e., [1], [4000]), ForkMV is able to estimate the mean response time within 5 % and 15 % and variance response time within 15% and 10% of the simulation results for short-tailed exponential service distribution and long-tailed truncated Pareto distribution, respectively, at the 90 % load or higher.