[processor/transform] Add functions for conversion of scalar metric types

CHANGELOG.md

@@ -19,6 +19,7 @@
 
 - `tailsamplingprocessor`: Add support for string invert matching to `and` policy (#9553)
 - `mezemoexporter`: Add user agent string to outgoing HTTP requests (#10470)
+- `transformprocessor`: Add functions for conversion of scalar metric types (`gauge_to_sum` and `sum_to_gauge`) (#10255)
 
 ### 🧰 Bug fixes 🧰
 

processor/transformprocessor/README.md

@@ -37,6 +37,13 @@ the fields specified by the list of strings. e.g., `keep_keys(attributes, "http.
 
 - `replace_all_matches(target, pattern, replacement)` - `target` is a path expression to a map type field, `pattern` is a string following [filepath.Match syntax](https://pkg.go.dev/path/filepath#Match), and `replacement` is a string. Each string value in `target` that matches `pattern` will get replaced with `replacement`. e.g., `replace_all_matches(attributes, "/user/*/list/*", "/user/{userId}/list/{listId}")`
 
+Metric only functions:
+- `convert_sum_to_gauge()` - Converts incoming metrics of type "Sum" to type "Gauge", retaining the metric's datapoints. Noop for metrics that are not of type "Sum". 
+**NOTE:** This function may cause a metric to break semantics for [Gauge metrics](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/datamodel.md#gauge). Use at your own risk.
+
+- `convert_gauge_to_sum(aggregation_temporality, is_monotonic)` - `aggregation_temporality` specifies the resultant metric's aggregation temporality. `aggregation_temporality` may be `"cumulative"` or `"delta"`. `is_monotonic` specifies the resultant metric's monotonicity. `is_monotonic` is a boolean. Converts incoming metrics of type "Gauge" to type "Sum", retaining the metric's datapoints and setting its aggregation temporality and monotonicity accordingly. Noop for metrics that are not of type "Gauge". 
+**NOTE:** This function may cause a metric to break semantics for [Sum metrics](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/datamodel.md#sums). Use at your own risk.
+
 Supported where operations:
 - `==` - matches telemetry where the values are equal to each other
 - `!=` - matches telemetry where the values are not equal to each other
@@ -70,6 +77,8 @@ processors:
         - limit(attributes, 100)
         - truncate_all(attributes, 4096)
         - truncate_all(resource.attributes, 4096)
+        - convert_sum_to_gauge() where metric.name == "system.processes.count"
+        - convert_gauge_to_sum("cumulative", false) where metric.name == "prometheus_metric"
     logs:
       queries:
         - set(severity_text, "FAIL") where body == "request failed"
@@ -108,6 +117,8 @@ All metrics and their data points
 4) Limit all data point attributes such that each data point has no more than 100 attributes.
 6) Truncate all data point attributes such that no string value has more than 4096 characters.
 7) Truncate all resource attributes such that no string value has more than 4096 characters.
+8) Convert all metrics with name `system.processes.count` from a Sum to Gauge.
+9) Convert all metrics with name `prometheus_metric` from Gauge to a cumulative, non-monotonic Sum.
 
 All logs
 

processor/transformprocessor/config_test.go

@@ -24,6 +24,7 @@ import (
 	"go.opentelemetry.io/collector/config"
 	"go.opentelemetry.io/collector/service/servicetest"
 
+	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor/internal/metrics"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor/internal/traces"
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor/internal/logs"
@@ -56,7 +57,7 @@ func TestLoadingConfig(t *testing.T) {
 				`keep_keys(attributes, "http.method", "http.path")`,
 			},
 
-			functions: traces.DefaultFunctions(),
+			functions: metrics.DefaultFunctions(),
 		},
 		Logs: SignalConfig{
 			Queries: []string{

processor/transformprocessor/factory_test.go

@@ -27,6 +27,7 @@ import (
 	"go.opentelemetry.io/collector/pdata/pmetric"
 	"go.opentelemetry.io/collector/pdata/ptrace"
 
+	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor/internal/metrics"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor/internal/traces"
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor/internal/logs"
@@ -50,7 +51,7 @@ func TestFactory_CreateDefaultConfig(t *testing.T) {
 		Metrics: SignalConfig{
 			Queries: []string{},
 
-			functions: traces.DefaultFunctions(),
+			functions: metrics.DefaultFunctions(),
 		},
 		Logs: SignalConfig{
 			Queries: []string{},

processor/transformprocessor/internal/common/functions.go

@@ -247,6 +247,11 @@ func NewFunctionCall(inv Invocation, functions map[string]interface{}, pathParse
 					return nil, fmt.Errorf("invalid argument at position %v, must be a string", i)
 				}
 				args = append(args, reflect.ValueOf(*argDef.String))
+			case "bool":
+				if argDef.Bool == nil {
+					return nil, fmt.Errorf("invalid argument at position %v, must be a bool", i)
+				}
+				args = append(args, reflect.ValueOf(bool(*argDef.Bool)))
 			}
 		}
 		val := reflect.ValueOf(f)

processor/transformprocessor/internal/common/parser.go

@@ -20,6 +20,15 @@ import (
 	"go.uber.org/multierr"
 )
 
+// Type for capturing booleans, see:
+// https://github.com/alecthomas/participle#capturing-boolean-value
+type Boolean bool
+
+func (b *Boolean) Capture(values []string) error {
+	*b = values[0] == "true"
+	return nil
+}
+
 // ParsedQuery represents a parsed query. It is the entry point into the query DSL.
 // nolint:govet
 type ParsedQuery struct {
@@ -50,6 +59,7 @@ type Value struct {
 	String     *string     `| @String`
 	Float      *float64    `| @Float`
 	Int        *int64      `| @Int`
+	Bool       *Boolean    `| @("true" | "false")`
 	Path       *Path       `| @@ )`
 }
 

processor/transformprocessor/internal/common/parser_test.go

@@ -278,6 +278,40 @@ func Test_parse(t *testing.T) {
 				Condition: nil,
 			},
 		},
+		{
+			query: `convert_gauge_to_sum("cumulative", false)`,
+			expected: &ParsedQuery{
+				Invocation: Invocation{
+					Function: "convert_gauge_to_sum",
+					Arguments: []Value{
+						{
+							String: testhelper.Strp("cumulative"),
+						},
+						{
+							Bool: (*Boolean)(testhelper.Boolp(false)),
+						},
+					},
+				},
+				Condition: nil,
+			},
+		},
+		{
+			query: `convert_gauge_to_sum("cumulative", true)`,
+			expected: &ParsedQuery{
+				Invocation: Invocation{
+					Function: "convert_gauge_to_sum",
+					Arguments: []Value{
+						{
+							String: testhelper.Strp("cumulative"),
+						},
+						{
+							Bool: (*Boolean)(testhelper.Boolp(true)),
+						},
+					},
+				},
+				Condition: nil,
+			},
+		},
 	}
 
 	for _, tt := range tests {

processor/transformprocessor/internal/common/testhelper/testhelper.go

@@ -25,3 +25,7 @@ func Floatp(f float64) *float64 {
 func Intp(i int64) *int64 {
 	return &i
 }
+
+func Boolp(b bool) *bool {
+	return &b
+}

processor/transformprocessor/internal/metrics/functions.go

@@ -15,10 +15,83 @@
 package metrics // import "github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor/internal/metrics"
 
 import (
+	"fmt"
+
+	"go.opentelemetry.io/collector/pdata/pmetric"
+
 	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor/internal/common"
 )
 
+// registry is a map of names to functions for metrics pipelines
+var registry = map[string]interface{}{
+	"convert_sum_to_gauge": convertSumToGauge,
+	"convert_gauge_to_sum": convertGaugeToSum,
+}
+
+func init() {
+	// Init metrics registry with default functions common to all signals
+	for k, v := range common.DefaultFunctions() {
+		registry[k] = v
+	}
+}
+
 func DefaultFunctions() map[string]interface{} {
-	// No metric-only functions yet.
-	return common.DefaultFunctions()
+	return registry
+}
+
+func convertSumToGauge() (common.ExprFunc, error) {
+	return func(ctx common.TransformContext) interface{} {
+		mtc, ok := ctx.(metricTransformContext)
+		if !ok {
+			return nil
+		}
+
+		metric := mtc.GetMetric()
+		if metric.DataType() != pmetric.MetricDataTypeSum {
+			return nil
+		}
+
+		dps := metric.Sum().DataPoints()
+
+		metric.SetDataType(pmetric.MetricDataTypeGauge)
+		// Setting the data type removed all the data points, so we must copy them back to the metric.
+		dps.CopyTo(metric.Gauge().DataPoints())
+
+		return nil
+	}, nil
+}
+
+func convertGaugeToSum(stringAggTemp string, monotonic bool) (common.ExprFunc, error) {
+	var aggTemp pmetric.MetricAggregationTemporality
+	switch stringAggTemp {
+	case "delta":
+		aggTemp = pmetric.MetricAggregationTemporalityDelta
+	case "cumulative":
+		aggTemp = pmetric.MetricAggregationTemporalityCumulative
+	default:
+		return nil, fmt.Errorf("unknown aggregation temporality: %s", stringAggTemp)
+	}
+
+	return func(ctx common.TransformContext) interface{} {
+		mtc, ok := ctx.(metricTransformContext)
+		if !ok {
+			return nil
+		}
+
+		metric := mtc.GetMetric()
+		if metric.DataType() != pmetric.MetricDataTypeGauge {
+			return nil
+		}
+
+		dps := metric.Gauge().DataPoints()
+
+		metric.SetDataType(pmetric.MetricDataTypeSum)
+		metric.Sum().SetAggregationTemporality(aggTemp)
+		metric.Sum().SetIsMonotonic(monotonic)
+
+		// Setting the data type removed all the data points, so we must copy them back to the metric.
+		dps.CopyTo(metric.Sum().DataPoints())
+
+		return nil
+	}, nil
 }