Elia Battiston | ac8d23f | 2022-03-14 17:54:56 +0100 | [diff] [blame] | 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 | } |