Service-Level Object
SLO 是根据 SLA 设定的系统可用性的目标。在 SRE 中，系统可用性需要量化，SLO 即是系统可用性在不同维度量化后的目标。SLO 由一个或多个 SLI 附加商业价值来实现。
SLO 是一种向组织、别的团队传达可靠性的手段。
A service-level objective (SLO) is a key element of a service-level agreement (SLA) between a service provider and a customer. SLOs are agreed upon as a means of measuring the performance of the Service Provider and are outlined as a way of avoiding disputes between the two parties based on misunderstanding.[1]
Availability, in SRE terms, defines whether a system is able to fulfill its intended function at a point in time. In addition to being used as a reporting tool, the historical availability measurement can also describe the probability that your system will perform as expected in the future.
When we set out to define the terms of SRE, we wanted to set a precise numerical target for system availability. We term this target the availability Service-Level Objective (SLO) of our system.[2]
The SLO may be composed of one or more quality of service (QoS) measurements (service level indicators, SLIs) that are combined to produce the SLO achievement value.[1:1]
SLI, or Service Level Indicator, represents a measurement of a service’s behavior. A good SLI measures your service from the perspective of your users. An example SLI can be the speed at which a web page loads.[3]