prometheus/rules/recording.go

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// Copyright 2013 The Prometheus 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 rules
import (
"fmt"
"html/template"
"github.com/prometheus/common/model"
"github.com/prometheus/prometheus/promql"
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"github.com/prometheus/prometheus/util/strutil"
)
// A RecordingRule records its vector expression into new timeseries.
type RecordingRule struct {
name string
vector promql.Expr
labels model.LabelSet
}
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// NewRecordingRule returns a new recording rule.
func NewRecordingRule(name string, vector promql.Expr, labels model.LabelSet) *RecordingRule {
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return &RecordingRule{
name: name,
vector: vector,
labels: labels,
}
}
// Name returns the rule name.
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func (rule RecordingRule) Name() string {
return rule.name
}
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// eval evaluates the rule and then overrides the metric names and labels accordingly.
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func (rule RecordingRule) eval(timestamp model.Time, engine *promql.Engine) (model.Vector, error) {
query, err := engine.NewInstantQuery(rule.vector.String(), timestamp)
if err != nil {
return nil, err
}
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var (
result = query.Exec()
vector model.Vector
)
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if result.Err != nil {
return nil, err
}
switch result.Value.(type) {
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case model.Vector:
vector, err = result.Vector()
if err != nil {
return nil, err
}
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case *model.Scalar:
scalar, err := result.Scalar()
if err != nil {
return nil, err
}
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vector = model.Vector{&model.Sample{
Value: scalar.Value,
Timestamp: scalar.Timestamp,
Metric: model.Metric{},
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}}
default:
return nil, fmt.Errorf("rule result is not a vector or scalar")
}
// Override the metric name and labels.
for _, sample := range vector {
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sample.Metric[model.MetricNameLabel] = model.LabelValue(rule.name)
for label, value := range rule.labels {
if value == "" {
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delete(sample.Metric, label)
} else {
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sample.Metric[label] = value
}
}
}
return vector, nil
}
func (rule RecordingRule) String() string {
return fmt.Sprintf("%s%s = %s\n", rule.name, rule.labels, rule.vector)
}
// HTMLSnippet returns an HTML snippet representing this rule.
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func (rule RecordingRule) HTMLSnippet(pathPrefix string) template.HTML {
ruleExpr := rule.vector.String()
return template.HTML(fmt.Sprintf(
`<a href="%s">%s</a>%s = <a href="%s">%s</a>`,
pathPrefix+strutil.GraphLinkForExpression(rule.name),
rule.name,
rule.labels,
pathPrefix+strutil.GraphLinkForExpression(ruleExpr),
ruleExpr))
}