forked from knative/eventing
/
history.go
78 lines (67 loc) · 2.23 KB
/
history.go
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/*
* Copyright 2018 The Knative Authors
*
* 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 channel
import (
"regexp"
"strings"
cloudevents "github.com/cloudevents/sdk-go"
)
const (
// EventHistory is the header containing all channel hosts traversed by the event.
// This is an experimental header: https://github.com/knative/eventing/issues/638.
EventHistory = "knativehistory"
EventHistorySeparator = "; "
)
var historySplitter = regexp.MustCompile(`\s*` + regexp.QuoteMeta(EventHistorySeparator) + `\s*`)
// AppendToHistory appends a new host at the end of the list of hosts of the event history.
func AppendHistory(event *cloudevents.Event, host string) {
host = cleanupEventHistoryItem(host)
if host == "" {
return
}
h := history(event)
setHistory(event, append(h, host))
}
// history returns the list of hosts where the event has been into.
func history(event *cloudevents.Event) []string {
var h string
if err := event.ExtensionAs(EventHistory, &h); err != nil {
return nil
}
return decodeEventHistory(h)
}
// setHistory sets the event history to the given value.
func setHistory(event *cloudevents.Event, history []string) {
event.SetExtension(EventHistory, encodeEventHistory(history))
}
func cleanupEventHistoryItem(host string) string {
return strings.Trim(host, " ")
}
func encodeEventHistory(history []string) string {
return strings.Join(history, EventHistorySeparator)
}
func decodeEventHistory(historyStr string) []string {
readHistory := historySplitter.Split(historyStr, -1)
// Filter and cleanup in-place
history := readHistory[:0]
for _, item := range readHistory {
cleanItem := cleanupEventHistoryItem(item)
if cleanItem != "" {
history = append(history, cleanItem)
}
}
return history
}