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schedule.go
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schedule.go
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// Copyright 2022 SAP SE or an SAP affiliate company. All rights reserved. This file is licensed under the Apache Software License, v. 2 except as noted otherwise in the LICENSE file
//
// 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 timewindow
import (
"fmt"
"hash/crc32"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/types"
)
// MutateScheduleFunc is a function for mutating the schedule based on the maintenance time window and UID.
type MutateScheduleFunc func(string, MaintenanceTimeWindow, types.UID) string
// DetermineSchedule determines a schedule based on the provided format and the creation timestamp. If both the begin
// and end of a maintenance time window are provided and different from the 'always time window' then the provided
// mutation function is applied.
func DetermineSchedule(
scheduleFormat string,
begin, end string,
uid types.UID,
creationTimestamp metav1.Time,
mutate MutateScheduleFunc,
) (
string,
error,
) {
if len(begin) != 0 && len(end) != 0 {
maintenanceTimeWindow, err := ParseMaintenanceTimeWindow(begin, end)
if err != nil {
return "", err
}
if !maintenanceTimeWindow.Equal(AlwaysTimeWindow) {
return mutate(scheduleFormat, *maintenanceTimeWindow, uid), nil
}
}
return fmt.Sprintf(scheduleFormat, creationTimestamp.Minute(), creationTimestamp.Hour()), nil
}
// RandomizeWithinTimeWindow computes a random time (based on the provided UID) within the provided time window.
func RandomizeWithinTimeWindow(scheduleFormat string, window MaintenanceTimeWindow, uid types.UID) string {
var (
windowBegin = window.Begin()
windowInMinutes = uint32(window.Duration().Minutes())
randomMinutes = int(crc32.ChecksumIEEE([]byte(uid)) % windowInMinutes)
randomTime = windowBegin.Add(0, randomMinutes, 0)
)
return fmt.Sprintf(scheduleFormat, randomTime.Minute(), randomTime.Hour())
}
// RandomizeWithinFirstHourOfTimeWindow computes a random time (based on the provided UID) within the first hour of the
// provided time window. It adds a 15 minutes time buffer before the start.
func RandomizeWithinFirstHourOfTimeWindow(scheduleFormat string, window MaintenanceTimeWindow, uid types.UID) string {
var (
windowBegin = window.Begin().Add(0, -15, 0)
randomMinutes = int(crc32.ChecksumIEEE([]byte(uid)) % 60)
randomTime = windowBegin.Add(-1, randomMinutes, 0)
)
return fmt.Sprintf(scheduleFormat, randomTime.Minute(), randomTime.Hour())
}