[processor/metricstransformprocessor]: Support median aggregation type (

#33655)

**Description:**
- use aggregation business logic from `interval/core`
- support `median` aggregation type
- testing
- docs

**Link to tracking Issue:** #16224 

**Depends on**
#33669

---------

Signed-off-by: odubajDT <ondrej.dubaj@dynatrace.com>
Co-authored-by: Evan Bradley <11745660+evan-bradley@users.noreply.github.com>

.chloggen/aggregation-metricstransformprocessor.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: metricstransformprocessor
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Adds the 'median' aggregation type to the Metrics Transform Processor. Also uses the refactored aggregation business logic from internal/core package."
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [16224]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

processor/metricstransformprocessor/README.md

@@ -86,7 +86,7 @@ processors:
         # new_name specifies the updated name of the metric; if action is insert or combine, new_name is required
         new_name: <new_metric_name_inserted>
         # aggregation_type defines how combined data points will be aggregated; if action is combine, aggregation_type is required
-        aggregation_type: {sum, mean, min, max, count}
+        aggregation_type: {sum, mean, min, max, count, median}
         # submatch_case specifies the case that should be used when adding label values based on regexp submatches when performing a combine action; leave blank to use the submatch value as is
         submatch_case: {lower, upper}
         # operations contain a list of operations that will be performed on the resulting metric(s)
@@ -106,7 +106,7 @@ processors:
             # label_set contains a list of labels that will remain after aggregation; if action is aggregate_labels, label_set is required
             label_set: [labels...]
             # aggregation_type defines how data points will be aggregated; if action is aggregate_labels or aggregate_label_values, aggregation_type is required
-            aggregation_type: {sum, mean, min, max, count}
+            aggregation_type: {sum, mean, min, max, count, median}
             # experimental_scale specifies the scalar to apply to values
             experimental_scale: <scalar>
             # value_actions contain a list of operations that will be performed on the selected label
@@ -273,6 +273,8 @@ operations:
     aggregation_type: sum
 ```
 
+**NOTE:** Only the `sum` aggregation function is supported for histogram and exponential histogram datatypes.
+
 ### Aggregate label values
 ```yaml
 # aggregate data points with state label value slab_reclaimable & slab_unreclaimable using summation into slab
@@ -286,6 +288,8 @@ operations:
     aggregation_type: sum
 ```
 
+**NOTE:** Only the `sum` aggregation function is supported for histogram and exponential histogram datatypes.
+
 ### Combine metrics
 ```yaml
 # convert a set of metrics for each http_method into a single metric with an http_method label, i.e.

processor/metricstransformprocessor/config.go

@@ -3,6 +3,8 @@
 
 package metricstransformprocessor // import "github.com/open-telemetry/opentelemetry-collector-contrib/processor/metricstransformprocessor"
 
+import "github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal/aggregateutil"
+
 const (
 	// includeFieldName is the mapstructure field name for Include field
 	includeFieldName = "include"
@@ -75,7 +77,7 @@ type transform struct {
 
 	// AggregationType specifies how to aggregate.
 	// REQUIRED only if Action is COMBINE.
-	AggregationType aggregationType `mapstructure:"aggregation_type"`
+	AggregationType aggregateutil.AggregationType `mapstructure:"aggregation_type"`
 
 	// SubmatchCase specifies what case to use for label values created from regexp submatches.
 	SubmatchCase submatchCase `mapstructure:"submatch_case"`
@@ -112,7 +114,7 @@ type Operation struct {
 	LabelSet []string `mapstructure:"label_set"`
 
 	// AggregationType specifies how to aggregate.
-	AggregationType aggregationType `mapstructure:"aggregation_type"`
+	AggregationType aggregateutil.AggregationType `mapstructure:"aggregation_type"`
 
 	// AggregatedValues is a list of label values to aggregate away.
 	AggregatedValues []string `mapstructure:"aggregated_values"`
@@ -216,38 +218,6 @@ func (oa operationAction) isValid() bool {
 	return false
 }
 
-// aggregationType is the enum to capture the three types of aggregation for the aggregation operation.
-type aggregationType string
-
-const (
-	// sum indicates taking the sum of the aggregated data.
-	sum aggregationType = "sum"
-
-	// mean indicates taking the mean of the aggregated data.
-	mean aggregationType = "mean"
-
-	// min indicates taking the minimum of the aggregated data.
-	min aggregationType = "min"
-
-	// max indicates taking the max of the aggregated data.
-	max aggregationType = "max"
-
-	// count indicates taking the count of the aggregated data.
-	count aggregationType = "count"
-)
-
-var aggregationTypes = []aggregationType{sum, mean, min, max, count}
-
-func (at aggregationType) isValid() bool {
-	for _, aggregationType := range aggregationTypes {
-		if at == aggregationType {
-			return true
-		}
-	}
-
-	return false
-}
-
 // matchType is the enum to capture the two types of matching metric(s) that should have operations applied to them.
 type matchType string
 

processor/metricstransformprocessor/factory.go

@@ -14,6 +14,7 @@ import (
 	"go.opentelemetry.io/collector/processor"
 	"go.opentelemetry.io/collector/processor/processorhelper"
 
+	"github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal/aggregateutil"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/metricstransformprocessor/internal/metadata"
 )
 
@@ -88,8 +89,8 @@ func validateConfiguration(config *Config) error {
 			return fmt.Errorf("missing required field %q while %q is %v", groupResourceLabelsFieldName, actionFieldName, Group)
 		}
 
-		if transform.AggregationType != "" && !transform.AggregationType.isValid() {
-			return fmt.Errorf("%q must be in %q", aggregationTypeFieldName, aggregationTypes)
+		if transform.AggregationType != "" && !transform.AggregationType.IsValid() {
+			return fmt.Errorf("%q must be in %q", aggregationTypeFieldName, aggregateutil.AggregationTypes)
 		}
 
 		if transform.SubmatchCase != "" && !transform.SubmatchCase.isValid() {
@@ -114,8 +115,8 @@ func validateConfiguration(config *Config) error {
 				return fmt.Errorf("operation %v: missing required field %q while %q is %v", i+1, scaleFieldName, actionFieldName, scaleValue)
 			}
 
-			if op.AggregationType != "" && !op.AggregationType.isValid() {
-				return fmt.Errorf("operation %v: %q must be in %q", i+1, aggregationTypeFieldName, aggregationTypes)
+			if op.AggregationType != "" && !op.AggregationType.IsValid() {
+				return fmt.Errorf("operation %v: %q must be in %q", i+1, aggregationTypeFieldName, aggregateutil.AggregationTypes)
 			}
 		}
 	}

processor/metricstransformprocessor/factory_test.go

@@ -16,6 +16,7 @@ import (
 	"go.opentelemetry.io/collector/consumer/consumertest"
 	"go.opentelemetry.io/collector/processor/processortest"
 
+	"github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal/aggregateutil"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/metricstransformprocessor/internal/metadata"
 )
 
@@ -87,7 +88,7 @@ func TestCreateProcessors(t *testing.T) {
 		{
 			configName:   "config_invalid_aggregationtype.yaml",
 			succeed:      false,
-			errorMessage: fmt.Sprintf("%q must be in %q", aggregationTypeFieldName, aggregationTypes),
+			errorMessage: fmt.Sprintf("%q must be in %q", aggregationTypeFieldName, aggregateutil.AggregationTypes),
 		},
 		{
 			configName:   "config_invalid_operation_action.yaml",
@@ -97,7 +98,7 @@ func TestCreateProcessors(t *testing.T) {
 		{
 			configName:   "config_invalid_operation_aggregationtype.yaml",
 			succeed:      false,
-			errorMessage: fmt.Sprintf("operation %v: %q must be in %q", 1, aggregationTypeFieldName, aggregationTypes),
+			errorMessage: fmt.Sprintf("operation %v: %q must be in %q", 1, aggregationTypeFieldName, aggregateutil.AggregationTypes),
 		},
 		{
 			configName:   "config_invalid_submatchcase.yaml",
@@ -221,14 +222,14 @@ func TestCreateProcessorsFilledData(t *testing.T) {
 				{
 					Action:          aggregateLabels,
 					LabelSet:        []string{"label1", "label2"},
-					AggregationType: sum,
+					AggregationType: aggregateutil.Sum,
 				},
 				{
 					Action:           aggregateLabelValues,
 					Label:            "label",
 					AggregatedValues: []string{"value1", "value2"},
 					NewValue:         "new-value",
-					AggregationType:  sum,
+					AggregationType:  aggregateutil.Sum,
 				},
 			},
 		},
@@ -265,7 +266,7 @@ func TestCreateProcessorsFilledData(t *testing.T) {
 					configOperation: Operation{
 						Action:          aggregateLabels,
 						LabelSet:        []string{"label1", "label2"},
-						AggregationType: sum,
+						AggregationType: aggregateutil.Sum,
 					},
 					labelSetMap: map[string]bool{
 						"label1": true,
@@ -278,7 +279,7 @@ func TestCreateProcessorsFilledData(t *testing.T) {
 						Label:            "label",
 						AggregatedValues: []string{"value1", "value2"},
 						NewValue:         "new-value",
-						AggregationType:  sum,
+						AggregationType:  aggregateutil.Sum,
 					},
 					aggregatedValuesSet: map[string]bool{
 						"value1": true,

processor/metricstransformprocessor/go.mod

@@ -3,6 +3,7 @@ module github.com/open-telemetry/opentelemetry-collector-contrib/processor/metri
 go 1.21.0
 
 require (
+	github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal v0.105.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/golden v0.105.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest v0.105.0
 	github.com/stretchr/testify v1.9.0
@@ -73,3 +74,5 @@ retract (
 )
 
 replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/golden => ../../pkg/golden
+
+replace github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal => ../../internal/coreinternal

processor/metricstransformprocessor/metrics_transform_processor.go

@@ -10,6 +10,8 @@ import (
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pmetric"
 	"go.uber.org/zap"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal/aggregateutil"
 )
 
 type metricsTransformProcessor struct {
@@ -23,7 +25,7 @@ type internalTransform struct {
 	Action              ConfigAction
 	NewName             string
 	GroupResourceLabels map[string]string
-	AggregationType     aggregationType
+	AggregationType     aggregateutil.AggregationType
 	SubmatchCase        submatchCase
 	Operations          []internalOperation
 }

processor/metricstransformprocessor/metrics_transform_processor_otlp.go

@@ -10,6 +10,8 @@ import (
 
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pmetric"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal/aggregateutil"
 )
 
 // extractAndRemoveMatchedMetrics extracts matched metrics from ms metric slice and returns a new slice.
@@ -440,6 +442,17 @@ func combine(transform internalTransform, metrics pmetric.MetricSlice) pmetric.M
 	return combinedMetric
 }
 
+// groupMetrics groups all the provided timeseries that will be aggregated together based on all the label values.
+// Returns a map of grouped timeseries and the corresponding selected labels
+// canBeCombined must be callled before.
+func groupMetrics(metrics pmetric.MetricSlice, aggType aggregateutil.AggregationType, to pmetric.Metric) {
+	ag := aggregateutil.AggGroups{}
+	for i := 0; i < metrics.Len(); i++ {
+		aggregateutil.GroupDataPoints(metrics.At(i), &ag)
+	}
+	aggregateutil.MergeDataPoints(to, aggType, ag)
+}
+
 func copyMetricDetails(from, to pmetric.Metric) {
 	to.SetName(from.Name())
 	to.SetUnit(from.Unit())
@@ -541,7 +554,13 @@ func transformMetric(metric pmetric.Metric, transform internalTransform) bool {
 			updateLabelOp(metric, op, transform.MetricIncludeFilter)
 		case aggregateLabels:
 			if canChangeMetric {
-				aggregateLabelsOp(metric, op)
+				attrs := []string{}
+				for k, v := range op.labelSetMap {
+					if v {
+						attrs = append(attrs, k)
+					}
+				}
+				aggregateLabelsOp(metric, attrs, op.configOperation.AggregationType)
 			}
 		case aggregateLabelValues:
 			if canChangeMetric {