mirror of https://github.com/kubernetes/kops.git
90 lines
2.2 KiB
Go
90 lines
2.2 KiB
Go
/*
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Copyright 2019 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package loader
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import (
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"fmt"
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"reflect"
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"k8s.io/klog"
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"k8s.io/kops/util/pkg/reflectutils"
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)
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const maxIterations = 10
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type OptionsLoader struct {
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Builders []OptionsBuilder
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}
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type OptionsBuilder interface {
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BuildOptions(options interface{}) error
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}
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func NewOptionsLoader(builders []OptionsBuilder) *OptionsLoader {
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l := &OptionsLoader{}
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l.Builders = builders
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return l
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}
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// iterate performs a single iteration of all the templates, executing each template in order
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func (l *OptionsLoader) iterate(userConfig interface{}, current interface{}) (interface{}, error) {
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t := reflect.TypeOf(current).Elem()
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next := reflect.New(t).Interface()
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// Copy the current state before applying rules; they act as defaults
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reflectutils.JSONMergeStruct(next, current)
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for _, t := range l.Builders {
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klog.V(2).Infof("executing builder %T", t)
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err := t.BuildOptions(next)
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if err != nil {
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return nil, err
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}
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}
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// Also copy the user-provided values after applying rules; they act as overrides now
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reflectutils.JSONMergeStruct(next, userConfig)
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return next, nil
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}
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// Build executes the options configuration templates, until they converge
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// It bails out after maxIterations
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func (l *OptionsLoader) Build(userConfig interface{}) (interface{}, error) {
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options := userConfig
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iteration := 0
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for {
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nextOptions, err := l.iterate(userConfig, options)
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if err != nil {
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return nil, err
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}
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if reflect.DeepEqual(options, nextOptions) {
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return options, nil
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}
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iteration++
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if iteration > maxIterations {
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return nil, fmt.Errorf("options did not converge after %d iterations", maxIterations)
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}
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options = nextOptions
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}
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}
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