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Diffstat (limited to 'src/runtime/pprof/label.go')
-rw-r--r-- | src/runtime/pprof/label.go | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/src/runtime/pprof/label.go b/src/runtime/pprof/label.go new file mode 100644 index 0000000..d39e0ad --- /dev/null +++ b/src/runtime/pprof/label.go @@ -0,0 +1,108 @@ +// Copyright 2016 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package pprof + +import ( + "context" + "fmt" + "sort" + "strings" +) + +type label struct { + key string + value string +} + +// LabelSet is a set of labels. +type LabelSet struct { + list []label +} + +// labelContextKey is the type of contextKeys used for profiler labels. +type labelContextKey struct{} + +func labelValue(ctx context.Context) labelMap { + labels, _ := ctx.Value(labelContextKey{}).(*labelMap) + if labels == nil { + return labelMap(nil) + } + return *labels +} + +// labelMap is the representation of the label set held in the context type. +// This is an initial implementation, but it will be replaced with something +// that admits incremental immutable modification more efficiently. +type labelMap map[string]string + +// String satisfies Stringer and returns key, value pairs in a consistent +// order. +func (l *labelMap) String() string { + if l == nil { + return "" + } + keyVals := make([]string, 0, len(*l)) + + for k, v := range *l { + keyVals = append(keyVals, fmt.Sprintf("%q:%q", k, v)) + } + + sort.Strings(keyVals) + + return "{" + strings.Join(keyVals, ", ") + "}" +} + +// WithLabels returns a new context.Context with the given labels added. +// A label overwrites a prior label with the same key. +func WithLabels(ctx context.Context, labels LabelSet) context.Context { + parentLabels := labelValue(ctx) + childLabels := make(labelMap, len(parentLabels)) + // TODO(matloob): replace the map implementation with something + // more efficient so creating a child context WithLabels doesn't need + // to clone the map. + for k, v := range parentLabels { + childLabels[k] = v + } + for _, label := range labels.list { + childLabels[label.key] = label.value + } + return context.WithValue(ctx, labelContextKey{}, &childLabels) +} + +// Labels takes an even number of strings representing key-value pairs +// and makes a LabelSet containing them. +// A label overwrites a prior label with the same key. +// Currently only the CPU and goroutine profiles utilize any labels +// information. +// See https://golang.org/issue/23458 for details. +func Labels(args ...string) LabelSet { + if len(args)%2 != 0 { + panic("uneven number of arguments to pprof.Labels") + } + list := make([]label, 0, len(args)/2) + for i := 0; i+1 < len(args); i += 2 { + list = append(list, label{key: args[i], value: args[i+1]}) + } + return LabelSet{list: list} +} + +// Label returns the value of the label with the given key on ctx, and a boolean indicating +// whether that label exists. +func Label(ctx context.Context, key string) (string, bool) { + ctxLabels := labelValue(ctx) + v, ok := ctxLabels[key] + return v, ok +} + +// ForLabels invokes f with each label set on the context. +// The function f should return true to continue iteration or false to stop iteration early. +func ForLabels(ctx context.Context, f func(key, value string) bool) { + ctxLabels := labelValue(ctx) + for k, v := range ctxLabels { + if !f(k, v) { + break + } + } +} |