1 // Copyright 2016 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
16 // LabelSet is a set of labels.
17 type LabelSet struct {
21 // labelContextKey is the type of contextKeys used for profiler labels.
22 type labelContextKey struct{}
24 func labelValue(ctx context.Context) labelMap {
25 labels, _ := ctx.Value(labelContextKey{}).(*labelMap)
32 // labelMap is the representation of the label set held in the context type.
33 // This is an initial implementation, but it will be replaced with something
34 // that admits incremental immutable modification more efficiently.
35 type labelMap map[string]string
37 // WithLabels returns a new context.Context with the given labels added.
38 // A label overwrites a prior label with the same key.
39 func WithLabels(ctx context.Context, labels LabelSet) context.Context {
40 childLabels := make(labelMap)
41 parentLabels := labelValue(ctx)
42 // TODO(matloob): replace the map implementation with something
43 // more efficient so creating a child context WithLabels doesn't need
45 for k, v := range parentLabels {
48 for _, label := range labels.list {
49 childLabels[label.key] = label.value
51 return context.WithValue(ctx, labelContextKey{}, &childLabels)
54 // Labels takes an even number of strings representing key-value pairs
55 // and makes a LabelList containing them.
56 // A label overwrites a prior label with the same key.
57 func Labels(args ...string) LabelSet {
59 panic("uneven number of arguments to pprof.Labels")
62 for i := 0; i+1 < len(args); i += 2 {
63 labels.list = append(labels.list, label{key: args[i], value: args[i+1]})
68 // Label returns the value of the label with the given key on ctx, and a boolean indicating
69 // whether that label exists.
70 func Label(ctx context.Context, key string) (string, bool) {
71 ctxLabels := labelValue(ctx)
72 v, ok := ctxLabels[key]
76 // ForLabels invokes f with each label set on the context.
77 // The function f should return true to continue iteration or false to stop iteration early.
78 func ForLabels(ctx context.Context, f func(key, value string) bool) {
79 ctxLabels := labelValue(ctx)
80 for k, v := range ctxLabels {