micro/metadata/metadata.go

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// Package metadata is a way of defining message headers
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package metadata
import (
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"context"
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)
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type metaKey struct{}
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// Metadata is our way of representing request headers internally.
// They're used at the RPC level and translate back and forth
// from Transport headers.
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type Metadata map[string]string
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// Copy makes a copy of the metadata
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func Copy(md Metadata) Metadata {
cmd := make(Metadata)
for k, v := range md {
cmd[k] = v
}
return cmd
}
// Get returns a single value from metadata in the context
func Get(ctx context.Context, key string) (string, bool) {
md, ok := FromContext(ctx)
if !ok {
return "", ok
}
val, ok := md[key]
return val, ok
}
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// FromContext returns metadata from the given context
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func FromContext(ctx context.Context) (Metadata, bool) {
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md, ok := ctx.Value(metaKey{}).(Metadata)
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return md, ok
}
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// NewContext creates a new context with the given metadata
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func NewContext(ctx context.Context, md Metadata) context.Context {
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return context.WithValue(ctx, metaKey{}, md)
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}
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// MergeContext merges metadata to existing metadata, overwriting if specified
func MergeContext(ctx context.Context, patchMd Metadata, overwrite bool) context.Context {
md, _ := ctx.Value(metaKey{}).(Metadata)
cmd := make(Metadata)
for k, v := range md {
cmd[k] = v
}
for k, v := range patchMd {
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if _, ok := cmd[k]; ok && !overwrite {
// skip
} else {
cmd[k] = v
}
}
return context.WithValue(ctx, metaKey{}, cmd)
}