github.com/m3db/m3@v1.5.0/src/metrics/transformation/binary.go (about)

     1  // Copyright (c) 2018 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 transformation
    22  
    23  import (
    24  	"math"
    25  	"time"
    26  )
    27  
    28  const (
    29  	nanosPerSecond = time.Second / time.Nanosecond
    30  )
    31  
    32  var (
    33  	// allows to use a single transform fn ref (instead of
    34  	// taking reference to it each time when converting to iface).
    35  	transformPerSecondFn = BinaryTransformFn(perSecond)
    36  	transformIncreaseFn  = BinaryTransformFn(increase)
    37  )
    38  
    39  func transformPerSecond() BinaryTransform {
    40  	return transformPerSecondFn
    41  }
    42  
    43  // perSecond computes the derivative between consecutive datapoints, taking into
    44  // account the time interval between the values.
    45  // Note:
    46  // * It skips NaN values.
    47  // * It assumes the timestamps are monotonically increasing, and values are non-decreasing.
    48  //   If either of the two conditions is not met, an empty datapoint is returned.
    49  func perSecond(prev, curr Datapoint, flags FeatureFlags) Datapoint {
    50  	if prev.TimeNanos >= curr.TimeNanos || math.IsNaN(prev.Value) || math.IsNaN(curr.Value) {
    51  		return emptyDatapoint
    52  	}
    53  	diff := curr.Value - prev.Value
    54  	if diff < 0 {
    55  		return emptyDatapoint
    56  	}
    57  	rate := diff * float64(nanosPerSecond) / float64(curr.TimeNanos-prev.TimeNanos)
    58  	return Datapoint{TimeNanos: curr.TimeNanos, Value: rate}
    59  }
    60  
    61  func transformIncrease() BinaryTransform {
    62  	return transformIncreaseFn
    63  }
    64  
    65  // increase computes the difference between consecutive datapoints, unlike
    66  // perSecond it does not account for the time interval between the values.
    67  // Note:
    68  // * It skips NaN values. If the previous value is a NaN value, it uses a previous value of 0.
    69  // * It assumes the timestamps are monotonically increasing, and values are non-decreasing.
    70  //   If either of the two conditions is not met, an empty datapoint is returned.
    71  func increase(prev, curr Datapoint, _ FeatureFlags) Datapoint {
    72  	if prev.TimeNanos >= curr.TimeNanos {
    73  		return emptyDatapoint
    74  	}
    75  	if math.IsNaN(curr.Value) {
    76  		return emptyDatapoint
    77  	}
    78  
    79  	if math.IsNaN(prev.Value) {
    80  		prev.Value = 0
    81  	}
    82  
    83  	diff := curr.Value - prev.Value
    84  	if diff < 0 {
    85  		return emptyDatapoint
    86  	}
    87  	return Datapoint{TimeNanos: curr.TimeNanos, Value: diff}
    88  }