google.golang.org/grpc@v1.72.2/internal/balancer/weight/weight.go (about)

     1  /*
     2   *
     3   * Copyright 2025 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  
    19  // Package weight contains utilities to manage endpoint weights. Weights are
    20  // used by LB policies such as ringhash to distribute load across multiple
    21  // endpoints.
    22  package weight
    23  
    24  import (
    25  	"fmt"
    26  
    27  	"google.golang.org/grpc/resolver"
    28  )
    29  
    30  // attributeKey is the type used as the key to store EndpointInfo in the
    31  // Attributes field of resolver.Endpoint.
    32  type attributeKey struct{}
    33  
    34  // EndpointInfo will be stored in the Attributes field of Endpoints in order to
    35  // use the ringhash balancer.
    36  type EndpointInfo struct {
    37  	Weight uint32
    38  }
    39  
    40  // Equal allows the values to be compared by Attributes.Equal.
    41  func (a EndpointInfo) Equal(o any) bool {
    42  	oa, ok := o.(EndpointInfo)
    43  	return ok && oa.Weight == a.Weight
    44  }
    45  
    46  // Set returns a copy of endpoint in which the Attributes field is updated with
    47  // EndpointInfo.
    48  func Set(endpoint resolver.Endpoint, epInfo EndpointInfo) resolver.Endpoint {
    49  	endpoint.Attributes = endpoint.Attributes.WithValue(attributeKey{}, epInfo)
    50  	return endpoint
    51  }
    52  
    53  // String returns a human-readable representation of EndpointInfo.
    54  // This method is intended for logging, testing, and debugging purposes only.
    55  // Do not rely on the output format, as it is not guaranteed to remain stable.
    56  func (a EndpointInfo) String() string {
    57  	return fmt.Sprintf("Weight: %d", a.Weight)
    58  }
    59  
    60  // FromEndpoint returns the EndpointInfo stored in the Attributes field of an
    61  // endpoint. It returns an empty EndpointInfo if attribute is not found.
    62  func FromEndpoint(endpoint resolver.Endpoint) EndpointInfo {
    63  	v := endpoint.Attributes.Value(attributeKey{})
    64  	ei, _ := v.(EndpointInfo)
    65  	return ei
    66  }