github.com/go-graphite/carbonapi@v0.17.0/expr/functions/changed/function.go (about)

     1  package changed
     2  
     3  import (
     4  	"context"
     5  	"math"
     6  
     7  	"github.com/go-graphite/carbonapi/expr/helper"
     8  	"github.com/go-graphite/carbonapi/expr/interfaces"
     9  	"github.com/go-graphite/carbonapi/expr/types"
    10  	"github.com/go-graphite/carbonapi/pkg/parser"
    11  )
    12  
    13  type changed struct{}
    14  
    15  func GetOrder() interfaces.Order {
    16  	return interfaces.Any
    17  }
    18  
    19  func New(configFile string) []interfaces.FunctionMetadata {
    20  	res := make([]interfaces.FunctionMetadata, 0)
    21  	f := &changed{}
    22  	functions := []string{"changed"}
    23  	for _, n := range functions {
    24  		res = append(res, interfaces.FunctionMetadata{Name: n, F: f})
    25  	}
    26  	return res
    27  }
    28  
    29  // changed(SeriesList)
    30  func (f *changed) Do(ctx context.Context, eval interfaces.Evaluator, e parser.Expr, from, until int64, values map[parser.MetricRequest][]*types.MetricData) ([]*types.MetricData, error) {
    31  	args, err := helper.GetSeriesArg(ctx, eval, e.Arg(0), from, until, values)
    32  	if err != nil {
    33  		return nil, err
    34  	}
    35  
    36  	result := make([]*types.MetricData, len(args))
    37  	for i, a := range args {
    38  		r := a.CopyTag(e.Target()+"("+a.Name+")", a.Tags)
    39  		r.Values = make([]float64, len(a.Values))
    40  
    41  		prev := math.NaN()
    42  		for i, v := range a.Values {
    43  			if math.IsNaN(prev) {
    44  				prev = v
    45  				r.Values[i] = 0
    46  			} else if !math.IsNaN(v) && prev != v {
    47  				r.Values[i] = 1
    48  				prev = v
    49  			} else {
    50  				r.Values[i] = 0
    51  			}
    52  		}
    53  		result[i] = r
    54  	}
    55  	return result, nil
    56  }
    57  
    58  // Description is auto-generated description, based on output of https://github.com/graphite-project/graphite-web
    59  func (f *changed) Description() map[string]types.FunctionDescription {
    60  	return map[string]types.FunctionDescription{
    61  		"changed": {
    62  			Description: "Takes one metric or a wildcard seriesList.\nOutput 1 when the value changed, 0 when null or the same\n\nExample:\n\n.. code-block:: none\n\n  &target=changed(Server01.connections.handled)",
    63  			Function:    "changed(seriesList)",
    64  			Group:       "Special",
    65  			Module:      "graphite.render.functions",
    66  			Name:        "changed",
    67  			Params: []types.FunctionParam{
    68  				{
    69  					Name:     "seriesList",
    70  					Required: true,
    71  					Type:     types.SeriesList,
    72  				},
    73  			},
    74  			NameChange:   true, // name changed
    75  			ValuesChange: true, // values changed
    76  		},
    77  	}
    78  }