Decentralize API Server

jakubdyszkiewicz commented 2 years ago

Description

pkg/api-server tries to gather all the endpoints in one package. The result is that API Server takes a lot of dependencies and is very bloated.

func NewApiServer(
    resManager manager.ResourceManager,
    meshContextBuilder xds_context.MeshContextBuilder,
    wsManager customization.APIInstaller,
    defs []model.ResourceTypeDescriptor,
    cfg *kuma_cp.Config,
    enableGUI bool,
    metrics metrics.Metrics,
    getInstanceId func() string, getClusterId func() string,
    authenticator authn.Authenticator,
    access runtime.Access,
    envoyAdminClient admin.EnvoyAdminClient,
) (*ApiServer, error) {

What we should do instead is what we've done with pkg/dp-server package. Which is to provide the backbone of api-server, but define and register the endpoints in a corresponding packages. For example:

token endpoints should be defined and registered in pkg/tokens.
inspect endpoint should be defined and registered in pkg/inspect (or something similar)

As we are ramping up GUI work, I expect new APIs, which will make this problem worse. Testing is also much easier this way, because you don't need to build the whole API Server that now has dependency on MeshContextBuilder just to test /config.