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clientimpl_watchers.go
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/
clientimpl_watchers.go
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/*
*
* Copyright 2020 gRPC authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package xdsclient
import (
"context"
"fmt"
"sync"
"google.golang.org/grpc/xds/internal/xdsclient/xdsresource"
)
// WatchResource uses xDS to discover the resource associated with the provided
// resource name. The resource type implementation determines how xDS requests
// are sent out and how responses are deserialized and validated. Upon receipt
// of a response from the management server, an appropriate callback on the
// watcher is invoked.
func (c *clientImpl) WatchResource(rType xdsresource.Type, resourceName string, watcher xdsresource.ResourceWatcher) (cancel func()) {
// Return early if the client is already closed.
//
// The client returned from the top-level API is a ref-counted client which
// contains a pointer to `clientImpl`. When all references are released, the
// ref-counted client sets its pointer to `nil`. And if any watch APIs are
// made on such a closed client, we will get here with a `nil` receiver.
if c == nil || c.done.HasFired() {
logger.Warningf("Watch registered for name %q of type %q, but client is closed", rType.TypeName(), resourceName)
return func() {}
}
if err := c.resourceTypes.maybeRegister(rType); err != nil {
logger.Warningf("Watch registered for name %q of type %q which is already registered", rType.TypeName(), resourceName)
c.serializer.Schedule(func(context.Context) { watcher.OnError(err) })
return func() {}
}
// TODO: replace this with the code does the following when we have
// implemented generic watch API on the authority:
// - Parse the resource name and extract the authority.
// - Locate the corresponding authority object and acquire a reference to
// it. If the authority is not found, error out.
// - Call the watchResource() method on the authority.
// - Return a cancel function to cancel the watch on the authority and to
// release the reference.
// TODO: Make ParseName return an error if parsing fails, and
// schedule the OnError callback in that case.
n := xdsresource.ParseName(resourceName)
a, unref, err := c.findAuthority(n)
if err != nil {
logger.Warningf("Watch registered for name %q of type %q, authority %q is not found", rType.TypeName(), resourceName, n.Authority)
c.serializer.Schedule(func(context.Context) { watcher.OnError(err) })
return func() {}
}
cancelF := a.watchResource(rType, n.String(), watcher)
return func() {
cancelF()
unref()
}
}
// A registry of xdsresource.Type implementations indexed by their corresponding
// type URLs. Registration of an xdsresource.Type happens the first time a watch
// for a resource of that type is invoked.
type resourceTypeRegistry struct {
mu sync.Mutex
types map[string]xdsresource.Type
}
func newResourceTypeRegistry() *resourceTypeRegistry {
return &resourceTypeRegistry{types: make(map[string]xdsresource.Type)}
}
func (r *resourceTypeRegistry) get(url string) xdsresource.Type {
r.mu.Lock()
defer r.mu.Unlock()
return r.types[url]
}
func (r *resourceTypeRegistry) maybeRegister(rType xdsresource.Type) error {
r.mu.Lock()
defer r.mu.Unlock()
url := rType.TypeURL()
typ, ok := r.types[url]
if ok && typ != rType {
return fmt.Errorf("attempt to re-register a resource type implementation for %v", rType.TypeName())
}
r.types[url] = rType
return nil
}
func (c *clientImpl) triggerResourceNotFoundForTesting(rType xdsresource.Type, resourceName string) error {
// Return early if the client is already closed.
if c == nil || c.done.HasFired() {
return fmt.Errorf("attempt to trigger resource-not-found-error for resource %q of type %q, but client is closed", rType.TypeName(), resourceName)
}
n := xdsresource.ParseName(resourceName)
a, unref, err := c.findAuthority(n)
if err != nil {
return fmt.Errorf("attempt to trigger resource-not-found-error for resource %q of type %q, but authority %q is not found", rType.TypeName(), resourceName, n.Authority)
}
defer unref()
a.triggerResourceNotFoundForTesting(rType, n.String())
return nil
}