GAMMA Support - Cilium

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.. _gs_gamma:

GAMMA Support

What is GAMMA? ####################

(From the GAMMA page <https://gateway-api.sigs.k8s.io/mesh/gamma/>__ on the Gateway API site):

The GAMMA initiative is a dedicated workstream within the Gateway API subproject, shepherded by the GAMMA leads, rather than being a separate subproject. GAMMA’s goal is to define how Gateway API can be used to configure a service mesh, with the intention of making minimal changes to Gateway API and always preserving the role-oriented nature of Gateway API. Additionally, GAMMA strives to advocate for consistency between implementations of Gateway API by service mesh projects, regardless of their technology stack or proxy.

In Gateway API v1.0, GAMMA supports adding extra HTTP routing to Services by binding a HTTPRoute to a Service as a parent (as opposed to the north/south Gateway API usage of binding a HTTPRoute to a Gateway as a parent).

This allows Cilium to intercept layer 7 traffic flowing to a parent Service and route the traffic through the per-node Envoy proxy. Because of this, GAMMA performs the same function as Cilium's :ref:Layer 7 traffic management <gs_l7_traffic_management>, without the user needing to know anything about configuring Envoy directly.

Types of GAMMA configuration ############################

In GAMMA, there are two types of HTTPRoutes: "producer" and "consumer" Routes.

"Producer" routes are HTTPRoutes that bind to a Service that lives in the same namespace and have the same owner as the owner of the Service whose traffic is being managed. So, for an application foo, in the namespace foo, with a Service called foo-svc, the owner of foo would create a HTTPRoute in the foo namespace that lists foo-svc as its parent. The routing then affects all traffic coming to the foo service from the whole cluster, and is controlled by the "producer" of the foo service - its owner.

"Consumer" routes are HTTPRoutes that bind to a Service that lives in a different namespace than that Service. These Routes are called "consumer" Routes because they are owned by the consumer of the Service they bind to. For the foo Service above, a Route in the bar namespace, to be used by the app in that namespace, that binds to the foo-svc Service in the foo namespace is a consumer Service because it changes the routing for the bar service, which consumes the foo Service.

Cilium currently supports only "Producer" Routes, and so HTTPRoutes must be in the same namespace as the Service that they are binding to.

Cilium GAMMA Support ##########################

Cilium supports GAMMA v1.0.0 for the following resources:

HTTPRoute <https://gateway-api.sigs.k8s.io/api-types/httproute/>_
ReferenceGrant <https://gateway-api.sigs.k8s.io/api-types/referencegrant/>_

Cilium support is limited to passing the Core conformance
tests and two out of three Extended Mesh tests. Note that GAMMA is itself
experimental as at Gateway API v1.0.0.

Cilium currently does not support "consumer" HTTPRoutes, and so does not
support the MeshConsumerRoute feature of the Mesh conformance profile.

.. include:: installation.rst