google.golang.org/grpc@v1.62.1/xds/internal/xdsclient/clientimpl_watchers.go (about)

     1  /*
     2   *
     3   * Copyright 2020 gRPC authors.
     4   *
     5   * Licensed under the Apache License, Version 2.0 (the "License");
     6   * you may not use this file except in compliance with the License.
     7   * You may obtain a copy of the License at
     8   *
     9   *     http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   */
    17  
    18  package xdsclient
    19  
    20  import (
    21  	"context"
    22  	"fmt"
    23  	"sync"
    24  
    25  	"google.golang.org/grpc/xds/internal/xdsclient/xdsresource"
    26  )
    27  
    28  // WatchResource uses xDS to discover the resource associated with the provided
    29  // resource name. The resource type implementation determines how xDS requests
    30  // are sent out and how responses are deserialized and validated. Upon receipt
    31  // of a response from the management server, an appropriate callback on the
    32  // watcher is invoked.
    33  func (c *clientImpl) WatchResource(rType xdsresource.Type, resourceName string, watcher xdsresource.ResourceWatcher) (cancel func()) {
    34  	// Return early if the client is already closed.
    35  	//
    36  	// The client returned from the top-level API is a ref-counted client which
    37  	// contains a pointer to `clientImpl`. When all references are released, the
    38  	// ref-counted client sets its pointer to `nil`. And if any watch APIs are
    39  	// made on such a closed client, we will get here with a `nil` receiver.
    40  	if c == nil || c.done.HasFired() {
    41  		logger.Warningf("Watch registered for name %q of type %q, but client is closed", rType.TypeName(), resourceName)
    42  		return func() {}
    43  	}
    44  
    45  	if err := c.resourceTypes.maybeRegister(rType); err != nil {
    46  		logger.Warningf("Watch registered for name %q of type %q which is already registered", rType.TypeName(), resourceName)
    47  		c.serializer.Schedule(func(context.Context) { watcher.OnError(err) })
    48  		return func() {}
    49  	}
    50  
    51  	// TODO: replace this with the code does the following when we have
    52  	// implemented generic watch API on the authority:
    53  	//  - Parse the resource name and extract the authority.
    54  	//  - Locate the corresponding authority object and acquire a reference to
    55  	//    it. If the authority is not found, error out.
    56  	//  - Call the watchResource() method on the authority.
    57  	//  - Return a cancel function to cancel the watch on the authority and to
    58  	//    release the reference.
    59  
    60  	// TODO: Make ParseName return an error if parsing fails, and
    61  	// schedule the OnError callback in that case.
    62  	n := xdsresource.ParseName(resourceName)
    63  	a, unref, err := c.findAuthority(n)
    64  	if err != nil {
    65  		logger.Warningf("Watch registered for name %q of type %q, authority %q is not found", rType.TypeName(), resourceName, n.Authority)
    66  		c.serializer.Schedule(func(context.Context) { watcher.OnError(err) })
    67  		return func() {}
    68  	}
    69  	cancelF := a.watchResource(rType, n.String(), watcher)
    70  	return func() {
    71  		cancelF()
    72  		unref()
    73  	}
    74  }
    75  
    76  // A registry of xdsresource.Type implementations indexed by their corresponding
    77  // type URLs. Registration of an xdsresource.Type happens the first time a watch
    78  // for a resource of that type is invoked.
    79  type resourceTypeRegistry struct {
    80  	mu    sync.Mutex
    81  	types map[string]xdsresource.Type
    82  }
    83  
    84  func newResourceTypeRegistry() *resourceTypeRegistry {
    85  	return &resourceTypeRegistry{types: make(map[string]xdsresource.Type)}
    86  }
    87  
    88  func (r *resourceTypeRegistry) get(url string) xdsresource.Type {
    89  	r.mu.Lock()
    90  	defer r.mu.Unlock()
    91  	return r.types[url]
    92  }
    93  
    94  func (r *resourceTypeRegistry) maybeRegister(rType xdsresource.Type) error {
    95  	r.mu.Lock()
    96  	defer r.mu.Unlock()
    97  
    98  	url := rType.TypeURL()
    99  	typ, ok := r.types[url]
   100  	if ok && typ != rType {
   101  		return fmt.Errorf("attempt to re-register a resource type implementation for %v", rType.TypeName())
   102  	}
   103  	r.types[url] = rType
   104  	return nil
   105  }
   106  
   107  func (c *clientImpl) triggerResourceNotFoundForTesting(rType xdsresource.Type, resourceName string) error {
   108  	// Return early if the client is already closed.
   109  	if c == nil || c.done.HasFired() {
   110  		return fmt.Errorf("attempt to trigger resource-not-found-error for resource %q of type %q, but client is closed", rType.TypeName(), resourceName)
   111  	}
   112  
   113  	n := xdsresource.ParseName(resourceName)
   114  	a, unref, err := c.findAuthority(n)
   115  	if err != nil {
   116  		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)
   117  	}
   118  	defer unref()
   119  	a.triggerResourceNotFoundForTesting(rType, n.String())
   120  	return nil
   121  }