[receiver/nginx] Add featuregate to emit 'nginx.connections_current' as a non-monotonic sum

.chloggen/nginx-connections-sum.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: nginxreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add featuregate to emit 'nginx.connections_current' as a non-monotonic sum
+
+# One or more tracking issues related to the change
+issues: [4326]
+
+# (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:

receiver/nginxreceiver/README.md

@@ -51,3 +51,15 @@ receivers:
 The full list of settings exposed for this receiver are documented [here](./config.go)
 with detailed sample configurations [here](./testdata/config.yaml).
 
+## Feature gate configurations
+
+See the [Collector feature gates](https://github.com/open-telemetry/opentelemetry-collector/blob/main/featuregate/README.md#collector-feature-gates) for an overview of feature gates in the collector.
+
+**ALPHA**: `receiver.nginx.emitCurrentConnectionsAsSum`
+
+The feature gate `receiver.nginx.emitConnectionsCurrentAsSum` once enabled will change the data type of the
+`nginx.connections_current` metric from a gauge to a non-monotonic sum.
+
+This feature gate will eventually be enabled by default, and eventually the old implementation will be removed. It aims
+to give users time to migrate to the new implementation. The target release for this featuregate to be enabled by default
+is 0.80.0.

receiver/nginxreceiver/documentation.md

@@ -49,3 +49,17 @@ Total number of requests made to the server since it started
 | Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic |
 | ---- | ----------- | ---------- | ----------------------- | --------- |
 | requests | Sum | Int | Cumulative | true |
+
+### temp.connections_current
+
+Temporary placeholder for new version of nginx.connections_current. See featuregate 'nginx.connections_as_sum'.
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic |
+| ---- | ----------- | ---------- | ----------------------- | --------- |
+| connections | Sum | Int | Cumulative | false |
+
+#### Attributes
+
+| Name | Description | Values |
+| ---- | ----------- | ------ |
+| state | The state of a connection | Str: ``active``, ``reading``, ``writing``, ``waiting`` |

receiver/nginxreceiver/factory.go

@@ -21,14 +21,24 @@ import (
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/config/confighttp"
 	"go.opentelemetry.io/collector/consumer"
+	"go.opentelemetry.io/collector/featuregate"
 	"go.opentelemetry.io/collector/receiver"
 	"go.opentelemetry.io/collector/receiver/scraperhelper"
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/nginxreceiver/internal/metadata"
 )
 
 const (
-	typeStr = "nginx"
+	typeStr          = "nginx"
+	connectionsAsSum = "receiver.nginx.emitConnectionsCurrentAsSum"
+)
+
+var connectorsAsSumGate = featuregate.GlobalRegistry().MustRegister(
+	connectionsAsSum,
+	featuregate.StageAlpha,
+	featuregate.WithRegisterDescription("When enabled, the receiver will emit the 'nginx.connections_current' metric as a nonmonotonic sum, rather than a gauge."),
+	featuregate.WithRegisterReferenceURL("https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/4326"),
+	featuregate.WithRegisterFromVersion("v0.78.0"),
 )
 
 // NewFactory creates a factory for nginx receiver.

receiver/nginxreceiver/go.mod

@@ -13,6 +13,7 @@ require (
 	go.opentelemetry.io/collector/component v0.77.0
 	go.opentelemetry.io/collector/confmap v0.77.0
 	go.opentelemetry.io/collector/consumer v0.77.0
+	go.opentelemetry.io/collector/featuregate v0.77.0
 	go.opentelemetry.io/collector/pdata v1.0.0-rcv0011
 	go.opentelemetry.io/collector/receiver v0.77.0
 	go.uber.org/zap v1.24.0
@@ -61,7 +62,6 @@ require (
 	github.com/sirupsen/logrus v1.9.0 // indirect
 	go.opencensus.io v0.24.0 // indirect
 	go.opentelemetry.io/collector/exporter v0.77.0 // indirect
-	go.opentelemetry.io/collector/featuregate v0.77.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.41.1 // indirect
 	go.opentelemetry.io/otel v1.15.1 // indirect
 	go.opentelemetry.io/otel/metric v0.38.1 // indirect

receiver/nginxreceiver/internal/metadata/testdata/config.yaml

@@ -9,6 +9,8 @@ all_set:
       enabled: true
     nginx.requests:
       enabled: true
+    temp.connections_current:
+      enabled: true
 none_set:
   metrics:
     nginx.connections_accepted:
@@ -19,3 +21,5 @@ none_set:
       enabled: false
     nginx.requests:
       enabled: false
+    temp.connections_current:
+      enabled: false

receiver/nginxreceiver/metadata.yaml

@@ -44,10 +44,23 @@ metrics:
       monotonic: true
       aggregation: cumulative
     attributes: []
+
+# Old version of metric, to be enabled when featuregate is stable
   nginx.connections_current:
     enabled: true
     description: The current number of nginx connections by state
     unit: connections
     gauge:
       value_type: int
     attributes: [state]
+
+# New version of metric, to be enabled when featuregate is stable
+  temp.connections_current:
+    enabled: true # must be enabled by default in order to apply necessary MetricBuilder option
+    description: Temporary placeholder for new version of nginx.connections_current. See featuregate 'nginx.connections_as_sum'.
+    unit: connections
+    sum:
+      value_type: int
+      monotonic: false
+      aggregation: cumulative
+    attributes: [state]

receiver/nginxreceiver/scraper.go

@@ -42,10 +42,16 @@ func newNginxScraper(
 	settings receiver.CreateSettings,
 	cfg *Config,
 ) *nginxScraper {
+	var mb *metadata.MetricsBuilder
+	if connectorsAsSumGate.IsEnabled() {
+		mb = metadata.NewMetricsBuilder(cfg.MetricsBuilderConfig, settings, metadata.WithCurrentConnectionsAsSum())
+	} else {
+		mb = metadata.NewMetricsBuilder(cfg.MetricsBuilderConfig, settings, metadata.WithCurrentConnectionsAsSumDisabled())
+	}
 	return &nginxScraper{
 		settings: settings.TelemetrySettings,
 		cfg:      cfg,
-		mb:       metadata.NewMetricsBuilder(cfg.MetricsBuilderConfig, settings),
+		mb:       mb,
 	}
 }
 
@@ -81,10 +87,18 @@ func (r *nginxScraper) scrape(context.Context) (pmetric.Metrics, error) {
 	r.mb.RecordNginxRequestsDataPoint(now, stats.Requests)
 	r.mb.RecordNginxConnectionsAcceptedDataPoint(now, stats.Connections.Accepted)
 	r.mb.RecordNginxConnectionsHandledDataPoint(now, stats.Connections.Handled)
-	r.mb.RecordNginxConnectionsCurrentDataPoint(now, stats.Connections.Active, metadata.AttributeStateActive)
-	r.mb.RecordNginxConnectionsCurrentDataPoint(now, stats.Connections.Reading, metadata.AttributeStateReading)
-	r.mb.RecordNginxConnectionsCurrentDataPoint(now, stats.Connections.Writing, metadata.AttributeStateWriting)
-	r.mb.RecordNginxConnectionsCurrentDataPoint(now, stats.Connections.Waiting, metadata.AttributeStateWaiting)
+
+	if connectorsAsSumGate.IsEnabled() {
+		r.mb.RecordTempConnectionsCurrentDataPoint(now, stats.Connections.Active, metadata.AttributeStateActive)
+		r.mb.RecordTempConnectionsCurrentDataPoint(now, stats.Connections.Reading, metadata.AttributeStateReading)
+		r.mb.RecordTempConnectionsCurrentDataPoint(now, stats.Connections.Writing, metadata.AttributeStateWriting)
+		r.mb.RecordTempConnectionsCurrentDataPoint(now, stats.Connections.Waiting, metadata.AttributeStateWaiting)
+	} else {
+		r.mb.RecordNginxConnectionsCurrentDataPoint(now, stats.Connections.Active, metadata.AttributeStateActive)
+		r.mb.RecordNginxConnectionsCurrentDataPoint(now, stats.Connections.Reading, metadata.AttributeStateReading)
+		r.mb.RecordNginxConnectionsCurrentDataPoint(now, stats.Connections.Writing, metadata.AttributeStateWriting)
+		r.mb.RecordNginxConnectionsCurrentDataPoint(now, stats.Connections.Waiting, metadata.AttributeStateWaiting)
+	}
 
 	return r.mb.Emit(), nil
 }