Control points are similar to feature flags. They identify the location in the code or data plane (web servers, service meshes, API gateways, and so on) where flow control decisions are applied. They're defined by developers using the SDKs or configured when integrating with API Gateways or Service Meshes.
How to Integrate Control Points
To empower Aperture to act at any of the control points, integrations need to be installed to be able to interact with the Aperture Agent. Here are the two primary types of control points: Feature control points and HTTP/gRPC control points.
Feature Control Points
Feature control points are facilitated by the Aperture SDKs, which are available for various popular programming languages. These SDKs allow any function call or code snippet within the service code to be wrapped as a feature control point. In Aperture's context, every execution of the feature is seen as a flow.
The SDK offers an API to initiate a flow, which corresponds to a
flowcontrol.v1.Check call into the Agent. The response
from this call comprises a decision on whether to accept or reject the flow. The
execution of a feature might be gated based on this decision. There is also an
API to end a flow, which creates an OpenTelemetry span representing the flow and
dispatches it to the Agent.
HTTP/gRPC Control Points
HTTP control points use web framework and service-mesh-based integrations to establish control points in the traffic path of a service.
In principle, any web proxy or web framework can be integrated with Aperture using this method. There are integrations available for many popular web frameworks.
The integration with Envoy uses the External Authorization API. In such a setup,
the control point can be used to identify a specific filter chain in Envoy. If
insertion is achieved using the
Istio integration, the
default filter configuration designates
egress control points as
of Istio's EnvoyFilter CRD.
Understanding Control Points
In the above diagram, each service has HTTP or gRPC control points. Every
incoming API request to a service is a flow at its
ingress control point.
Likewise, every outgoing request from a service is a flow at its
In addition, the
Frontend service has feature control points identifying
recommendations and live-update features inside the
The control point definition does not care about which particular entity (such as a pod) is handling a particular flow. A single control point covers all the entities belonging to the same service.
Live Preview of Control Points
aperturectl flow-control control-points
CLI command to list active control points.
aperturectl flow-control control-points --kube
AGENT GROUP SERVICE NAME TYPE
default service1-demo-app.demoapp.svc.cluster.local egress http
default service1-demo-app.demoapp.svc.cluster.local ingress http
default service2-demo-app.demoapp.svc.cluster.local egress http
default service2-demo-app.demoapp.svc.cluster.local ingress http
default service3-demo-app.demoapp.svc.cluster.local ingress http