ServiceControllers

监听底层平台的服务注册中心，缓存注册中心Istio服务模型，触发更新事件回调方法

# pilot/pkg/serviceregistry/aggregate/controller.go
// Controller aggregates data across different registries and monitors for changes
type Controller struct {
   registries []Registry
   storeLock  sync.RWMutex
}
// Registry specifies the collection of service registry related interfaces
type Registry struct {
   // Name is the type of the registry - Kubernetes, Consul, etc.
   Name serviceregistry.ServiceRegistry
   // ClusterID is used when multiple registries of the same type are used,
   // for example in the case of K8S multicluster.
   ClusterID string
   model.Controller
   model.ServiceDiscovery

}

type Controller struct {
   domainSuffix string

   client    kubernetes.Interface
   queue     kube.Queue
   services  cacheHandler
   endpoints cacheHandler
   nodes     cacheHandler

   pods *PodCache

   // Env is set by server to point to the environment, to allow the controller to
   // use env data and push status. It may be null in tests.
   Env *model.Environment

   // ClusterID identifies the remote cluster in a multicluster env.
   ClusterID string

   // XDSUpdater will push EDS changes to the ADS model.
   XDSUpdater model.XDSUpdater

   stop chan struct{}

   sync.RWMutex
   // servicesMap stores hostname ==> service, it is used to reduce convertService calls.
   servicesMap map[host.Name]*model.Service
   // externalNameSvcInstanceMap stores hostname ==> instance, is used to store instances for ExternalName k8s services
   externalNameSvcInstanceMap map[host.Name][]*model.ServiceInstance

   // CIDR ranger based on path-compressed prefix trie
   ranger cidranger.Ranger

   // Network name for the registry as specified by the MeshNetworks configmap
   networkForRegistry string

}

pilot/pkg/model/controller.go

pilot/pkg/model/service.go

核心逻辑

pilot/pkg/serviceregistry/kube/controller/controller.go

NewController

1，istio支持多集群，即pilot/pkg/serviceregistry/aggregate/controller.go下的Controller为一个总ServiceController，主要功能就是存放Registry对象
2，一个pilot/pkg/serviceregistry/aggregate/controller.go下的Registry对应一个集群注册中心，包含对应集群的Name和ClusterID，model.Controller和 model.ServiceDiscovery是监听与感知注册中心变化的操作类
3，Registry下的model.Controller和 model.ServiceDiscovery对象指向的都是pilot/pkg/serviceregistry/kube/controller/controller.go下的Controller
4，pilot/pkg/serviceregistry/kube/controller/controller.go下的Controller对象主要作用是利用cacheHandler对象监听注册中心中services，endpoints，nodes等对象的变化并缓存在本地
5，cacheHandler对象中的informer负责监听注册中心的变化，监听到变化之后，调用handler中的方法，执行预设的逻辑操作