Online Demand Scheduling with Failovers

Authors Konstantina Mellou, Marco Molinaro, Rudy Zhou

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Author Details

Konstantina Mellou
  • Microsoft Research, Redmond, WA, USA
Marco Molinaro
  • Microsoft Research, Redmond, WA, USA
  • PUC-Rio de Janeiro, Brazil
Rudy Zhou
  • Carnegie Mellon University, Pittsburgh, PA, USA


We thank the anonymous reviewers for their valuable suggestions. We also thank Alok Gautam Kumbhare and Ishai Menache for useful discussions.

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Konstantina Mellou, Marco Molinaro, and Rudy Zhou. Online Demand Scheduling with Failovers. In 50th International Colloquium on Automata, Languages, and Programming (ICALP 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 261, pp. 92:1-92:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


Motivated by cloud computing applications, we study the problem of how to optimally deploy new hardware subject to both power and robustness constraints. To model the situation observed in large-scale data centers, we introduce the Online Demand Scheduling with Failover problem. There are m identical devices with capacity constraints. Demands come one-by-one and, to be robust against a device failure, need to be assigned to a pair of devices. When a device fails (in a failover scenario), each demand assigned to it is rerouted to its paired device (which may now run at increased capacity). The goal is to assign demands to the devices to maximize the total utilization subject to both the normal capacity constraints as well as these novel failover constraints. These latter constraints introduce new decision tradeoffs not present in classic assignment problems such as the Multiple Knapsack problem and AdWords. In the worst-case model, we design a deterministic ≈ 1/2-competitive algorithm, and show this is essentially tight. To circumvent this constant-factor loss, which represents substantial capital losses for big cloud providers, we consider the stochastic arrival model, where all demands come i.i.d. from an unknown distribution. In this model we design an algorithm that achieves sub-linear additive regret (i.e. as OPT or m increases, the multiplicative competitive ratio goes to 1). This requires a combination of different techniques, including a configuration LP with a non-trivial post-processing step and an online monotone matching procedure introduced by Rhee and Talagrand.

Subject Classification

ACM Subject Classification
  • Theory of computation → Online algorithms
  • online algorithms
  • approximation algorithms
  • resource allocation


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