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correlation_context.go
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correlation_context.go
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// Copyright © 2019 The Things Network Foundation, The Things Industries B.V.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package events
import (
"context"
"crypto/rand"
"sort"
ulid "github.com/oklog/ulid/v2"
)
type correlationKey struct{}
// ContextWithCorrelationID returns a derived context with the correlation IDs if they were not already in there.
func ContextWithCorrelationID(ctx context.Context, cids ...string) context.Context {
cids = append(cids[:0:0], cids...)
sort.Strings(cids)
existing, ok := ctx.Value(correlationKey{}).([]string)
if !ok {
return context.WithValue(ctx, correlationKey{}, cids)
}
return context.WithValue(ctx, correlationKey{}, mergeStrings(existing, cids))
}
// CorrelationIDsFromContext returns the correlation IDs that are attached to the context.
func CorrelationIDsFromContext(ctx context.Context) []string {
cids, ok := ctx.Value(correlationKey{}).([]string)
if !ok {
return nil
}
return cids
}
// NewCorrelationID returns a new random correlation ID.
func NewCorrelationID() string {
return ulid.MustNew(ulid.Now(), rand.Reader).String()
}
// mergeStrings merges 2 sorted string slices and returns the resulting slice
// See https://en.wikipedia.org/wiki/Merge_sort
func mergeStrings(a, b []string) []string {
merged := make([]string, 0, len(a)+len(b))
var i, j int
for i < len(a) && j < len(b) {
if a[i] < b[j] {
merged = append(merged, a[i])
i++
} else if a[i] > b[j] {
merged = append(merged, b[j])
j++
} else {
merged = append(merged, a[i])
i++
j++
}
}
if i < len(a) {
merged = append(merged, a[i:]...)
} else if j < len(b) {
merged = append(merged, b[j:]...)
}
return merged
}