github.com/m3db/m3@v1.5.0/src/query/promqlengine/cache.go (about)

     1  // Copyright (c) 2021 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package promqlengine
    22  
    23  import (
    24  	"time"
    25  
    26  	"github.com/prometheus/prometheus/promql"
    27  )
    28  
    29  // NewEngineFn is a function to create a new promql.Engine with given lookback duration.
    30  type NewEngineFn func(lookbackDelta time.Duration) (*promql.Engine, error)
    31  
    32  // Cache caches PromQL engines by lookback duration.
    33  type Cache struct {
    34  	cachedEngines map[time.Duration]*promql.Engine
    35  	newEngineFn   NewEngineFn
    36  }
    37  
    38  // NewCache creates a new Cache.
    39  func NewCache(defaultEngines map[time.Duration]*promql.Engine, newEngineFn NewEngineFn) *Cache {
    40  	cachedEngines := make(map[time.Duration]*promql.Engine)
    41  	for l, e := range defaultEngines {
    42  		cachedEngines[l] = e
    43  	}
    44  	return &Cache{
    45  		cachedEngines: cachedEngines,
    46  		newEngineFn:   newEngineFn,
    47  	}
    48  }
    49  
    50  // Get returns a new or cached promql.Engine.
    51  func (c *Cache) Get(lookbackDelta time.Duration) (*promql.Engine, error) {
    52  	if engine, ok := c.cachedEngines[lookbackDelta]; ok {
    53  		return engine, nil
    54  	}
    55  
    56  	return c.newEngineFn(lookbackDelta)
    57  }