It Takes Two to Tango: Serverless Workflow Serving via Bilaterally Engaged Resource Adaptation

TL;DR

Janus introduces a dynamic resource adaptation framework for serverless workflows, enabling runtime-based function sizing that improves resource efficiency and maintains service-level objectives.

Contribution

Janus is the first framework to enable late-binding resource adaptation in serverless workflows, bridging the information gap between developers and providers.

Findings

Resource efficiency improved by up to 34.7%

Dynamic adaptation maintains SLO compliance

Effective in real-world serverless workflows

Abstract

Serverless platforms typically adopt an early-binding approach for function sizing, requiring developers to specify an immutable size for each function within a workflow beforehand. Accounting for potential runtime variability, developers must size functions for worst-case scenarios to ensure service-level objectives (SLOs), resulting in significant resource inefficiency. To address this issue, we propose Janus, a novel resource adaptation framework for serverless platforms. Janus employs a late-binding approach, allowing function sizes to be dynamically adapted based on runtime conditions. The main challenge lies in the information barrier between the developer and the provider: developers lack access to runtime information, while providers lack domain knowledge about the workflow. To bridge this gap, Janus allows developers to provide hints containing rules and options for resource adaptation. Providers then follow these hints to dynamically adjust resource allocation at runtime based on real-time function execution information, ensuring compliance with SLOs. We implement Janus and conduct extensive experiments with real-world serverless workflows. Our results demonstrate that Janus enhances resource efficiency by up to 34.7% compared to the state-of-the-art.