context.go

Documentation: github.com/grpc-ecosystem/go-grpc-middleware/tags

     1  package grpc_ctxtags
     2  
     3  import (
     4  	"context"
     5  )
     6  
     7  type ctxMarker struct{}
     8  
     9  var (
    10  	// ctxMarkerKey is the Context value marker used by *all* logging middleware.
    11  	// The logging middleware object must interf
    12  	ctxMarkerKey = &ctxMarker{}
    13  	// NoopTags is a trivial, minimum overhead implementation of Tags for which all operations are no-ops.
    14  	NoopTags = &noopTags{}
    15  )
    16  
    17  // Tags is the interface used for storing request tags between Context calls.
    18  // The default implementation is *not* thread safe, and should be handled only in the context of the request.
    19  type Tags interface {
    20  	// Set sets the given key in the metadata tags.
    21  	Set(key string, value interface{}) Tags
    22  	// Has checks if the given key exists.
    23  	Has(key string) bool
    24  	// Values returns a map of key to values.
    25  	// Do not modify the underlying map, please use Set instead.
    26  	Values() map[string]interface{}
    27  }
    28  
    29  type mapTags struct {
    30  	values map[string]interface{}
    31  }
    32  
    33  func (t *mapTags) Set(key string, value interface{}) Tags {
    34  	t.values[key] = value
    35  	return t
    36  }
    37  
    38  func (t *mapTags) Has(key string) bool {
    39  	_, ok := t.values[key]
    40  	return ok
    41  }
    42  
    43  func (t *mapTags) Values() map[string]interface{} {
    44  	return t.values
    45  }
    46  
    47  type noopTags struct{}
    48  
    49  func (t *noopTags) Set(key string, value interface{}) Tags {
    50  	return t
    51  }
    52  
    53  func (t *noopTags) Has(key string) bool {
    54  	return false
    55  }
    56  
    57  func (t *noopTags) Values() map[string]interface{} {
    58  	return nil
    59  }
    60  
    61  // Extracts returns a pre-existing Tags object in the Context.
    62  // If the context wasn't set in a tag interceptor, a no-op Tag storage is returned that will *not* be propagated in context.
    63  func Extract(ctx context.Context) Tags {
    64  	t, ok := ctx.Value(ctxMarkerKey).(Tags)
    65  	if !ok {
    66  		return NoopTags
    67  	}
    68  
    69  	return t
    70  }
    71  
    72  func SetInContext(ctx context.Context, tags Tags) context.Context {
    73  	return context.WithValue(ctx, ctxMarkerKey, tags)
    74  }
    75  
    76  func NewTags() Tags {
    77  	return &mapTags{values: make(map[string]interface{})}
    78  }
    79
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