Overload Control for Scaling WeChat Microservices

TL;DR

This paper introduces DAGOR, a system-centric overload control scheme for WeChat's microservices, which manages overload collaboratively at the microservice level to improve success rates and fairness during overload conditions.

Contribution

DAGOR is a novel, service-agnostic overload control approach that decouples overload management from service logic and operates system-wide for microservice architectures.

Findings

DAGOR maintains high service success rates under overload.

It ensures fairness in overload control among services.

DAGOR has been effectively used in WeChat for five years.

Abstract

Effective overload control for large-scale online service system is crucial for protecting the system backend from overload. Conventionally, the design of overload control is ad-hoc for individual service. However, service-specific overload control could be detrimental to the overall system due to intricate service dependencies or flawed implementation of service. Service developers usually have difficulty to accurately estimate the dynamics of actual workload during the development of service. Therefore, it is essential to decouple the overload control from service logic. In this paper, we propose DAGOR, an overload control scheme designed for the account-oriented microservice architecture. DAGOR is service agnostic and system-centric. It manages overload at the microservice granule such that each microservice monitors its load status in real time and triggers load shedding in a collaborative manner among its relevant services when overload is detected. DAGOR has been used in the WeChat backend for five years. Experimental results show that DAGOR can benefit high success rate of service even when the system is experiencing overload, while ensuring fairness in the overload control.