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cache.go
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cache.go
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// Copyright (c) 2021 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package promqlengine
import (
"time"
"github.com/prometheus/prometheus/promql"
)
// NewEngineFn is a function to create a new promql.Engine with given lookback duration.
type NewEngineFn func(lookbackDelta time.Duration) (*promql.Engine, error)
// Cache caches PromQL engines by lookback duration.
type Cache struct {
cachedEngines map[time.Duration]*promql.Engine
newEngineFn NewEngineFn
}
// NewCache creates a new Cache.
func NewCache(defaultEngines map[time.Duration]*promql.Engine, newEngineFn NewEngineFn) *Cache {
cachedEngines := make(map[time.Duration]*promql.Engine)
for l, e := range defaultEngines {
cachedEngines[l] = e
}
return &Cache{
cachedEngines: cachedEngines,
newEngineFn: newEngineFn,
}
}
// Get returns a new or cached promql.Engine.
func (c *Cache) Get(lookbackDelta time.Duration) (*promql.Engine, error) {
if engine, ok := c.cachedEngines[lookbackDelta]; ok {
return engine, nil
}
return c.newEngineFn(lookbackDelta)
}