72 lines
2.3 KiB
Go
72 lines
2.3 KiB
Go
/*
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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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https://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 cluster
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import (
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"fmt"
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"k8s.io/apimachinery/pkg/runtime"
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"k8s.io/client-go/util/jsonpath"
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)
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// An Expression is used to find information about a kubernetes resource. It
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// evaluates to a boolean when matched against a resource.
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type Expression struct {
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// A Condition describes a JSONPath filter which is matched against an
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// array containing a single resource.
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Condition string `json:"condition"`
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// jsonPath is used for the actual act of filtering on resources. It is
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// stored within the Expression as a means of memoization.
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jsonPath *jsonpath.JSONPath
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}
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// Match returns true if the given object matches the parsed jsonpath object.
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// An error is returned if the Expression's condition is not a valid JSONPath
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// as defined here: https://goessner.net/articles/JsonPath.
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func (e *Expression) Match(obj runtime.Unstructured) (bool, error) {
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// NOTE(howell): JSONPath filters only work on lists. This means that
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// in order to check if a certain condition is met for obj, we need to
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// put obj into an list, then see if the filter catches obj.
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const listName = "items"
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// Parse lazily
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if e.jsonPath == nil {
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jp := jsonpath.New("status-check")
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// The condition must be a filter on a list
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itemAsArray := fmt.Sprintf("{$.%s[?(%s)]}", listName, e.Condition)
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err := jp.Parse(itemAsArray)
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if err != nil {
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return false, ErrInvalidStatusCheck{
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What: fmt.Sprintf("unable to parse jsonpath %q: %v", e.Condition, err.Error()),
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}
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}
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e.jsonPath = jp
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}
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// Filters only work on lists
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list := map[string]interface{}{
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listName: []interface{}{obj.UnstructuredContent()},
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}
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results, err := e.jsonPath.FindResults(list)
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if err != nil {
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return false, ErrInvalidStatusCheck{
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What: fmt.Sprintf("failed to execute condition %q on object %v: %v", e.Condition, obj, err),
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}
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}
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return len(results[0]) == 1, nil
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}
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