This is SMI spec version v0.5.0. Learn more about versioning below.
The Service Mesh Interface (SMI) is a specification for service meshes that run on Kubernetes. It defines a common standard that can be implemented by a variety of providers. This allows for both standardization for end-users and innovation by providers of Service Mesh Technology. SMI enables flexibility and interoperability, and covers the most common service mesh capabilities.
The goal of the SMI API is to provide a common, portable set of Service Mesh APIs which a Kubernetes user can use in a provider agnostic manner. In this way people can define applications that use Service Mesh technology without tightly binding to any specific implementation.
It is a non-goal for the SMI project to implement a service mesh itself. It merely attempts to define the common specification. Likewise it is a non-goal to define the extent of what it means to be a Service Mesh, but rather a generally useful subset. If SMI providers want to add provider specific extensions and APIs beyond the SMI spec, they are welcome to do so. We expect that, over time, as more functionality becomes commonly accepted as part of what it means to be a Service Mesh, those definitions will migrate into the SMI specification.
The SMI is specified as a collection of Kubernetes APIs via Kubernetes Custom Resource Definitions (CRD) and Extension API Servers. These APIs can be installed onto any Kubernetes cluster and manipulated using standard tools. The APIs require an SMI provider to do something.
To activate these APIs an SMI provider is run in the Kubernetes cluster. For the resources that enable configuration, the SMI provider reflects back on their contents and configures the provider's components within a cluster to implement the desired behavior. In the case of extension APIs, the SMI provider translates from internal types to those the API expects to return.
This approach to pluggable interfaces is similar to other core Kubernetes APIs like NetworkPolicy, Ingress and CustomMetrics.
Find each API described at a high level below. Follow the links to see the individual API specification documents for the details. Each document outlines:
- Specification
- Possible use cases
- Example implementations
- Tradeoffs
Note: historical versions of the API specification as well as current working drafts can be found under the apis/ directory
Apply policies like identity and transport encryption across services.
The Traffic Access Control API describes a resource to configure access to specific pods and routes based on the identity of a client for locking down applications to only allowed users and services.
Shift traffic between different services.
The Traffic Split API describes a resource to incrementally direct percentages of traffic between various services to assist in building out canary rollouts.
Describe traffic on a per-protocol basis.
The Traffic Specs API describes a set of resources to define how traffic looks on a per-protocol basis. These resources work in concert with access control and other types of policy to manage traffic at a protocol level.
Capture key metrics like error rate and latency between services.
The Traffic Metrics API exposes common traffic metrics for use by tools such as dashboards and autoscalers.
- SMI Provider: An implementor of SMI. This could be a service mesh.
- API Group: A set of resources that are exposed together. Each group may have one or more versions that evolve independently of other API Groups. Group names are in domain form.
Please submit an issue or a pull request to this repository to propose a change. Changes are discussed on the SMI community meetings. Changes should be made to working draft documents of each API which can be found in the corresponding directories under apis/. Current working drafts documents have a suffix -WD.md
The spec has its own version listed above. This version describes the specification in its entirety. Although it is not related to the API specification versions, the minor version of the spec will be incremented every time any of the API Specification versions are incremented.