[receiver/wavefront] wrap metrics receiver under carbon receiver inst…

…ead of using export function (open-telemetry#27259)

**Description:** 
Wavefrontreceiver is very similar to carbonreceiver: it is TCP based in
which each received text line represents a single metric data point. In
order to avoid using exported function `carbonreceiver.New(...)`, we can
wrap metrics receiver under carbon receiver.

**Link to tracking Issue:** 

open-telemetry#27248

**Testing:** 
make chlog-validate
go test for wavefrontreceiver

**Documentation:**

---------

Co-authored-by: Pablo Baeyens <pbaeyens31+github@gmail.com>

.chloggen/fix-wavefront-metric-factory.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: wavefrontreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Wrap metrics receiver under carbon receiver instead of using export function
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [27248]
+
+# (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: []

receiver/wavefrontreceiver/factory.go

@@ -5,14 +5,13 @@ package wavefrontreceiver // import "github.com/open-telemetry/opentelemetry-col
 
 import (
 	"context"
+	"fmt"
 
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/config/confignet"
 	"go.opentelemetry.io/collector/consumer"
 	"go.opentelemetry.io/collector/receiver"
 
-	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/carbonreceiver"
-	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/carbonreceiver/protocol"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/carbonreceiver/transport"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/wavefrontreceiver/internal/metadata"
 )
@@ -42,27 +41,9 @@ func createMetricsReceiver(
 	cfg component.Config,
 	consumer consumer.Metrics,
 ) (receiver.Metrics, error) {
-
-	rCfg := cfg.(*Config)
-
-	// Wavefront is very similar to Carbon: it is TCP based in which each received
-	// text line represents a single metric data point. They differ on the format
-	// of their textual representation.
-	//
-	// The Wavefront receiver leverages the Carbon receiver code by implementing
-	// a dedicated parser for its format.
-	carbonCfg := carbonreceiver.Config{
-		NetAddr: confignet.NetAddr{
-			Endpoint:  rCfg.Endpoint,
-			Transport: "tcp",
-		},
-		TCPIdleTimeout: rCfg.TCPIdleTimeout,
-		Parser: &protocol.Config{
-			Type: "plaintext", // TODO: update after other parsers are implemented for Carbon receiver.
-			Config: &WavefrontParser{
-				ExtractCollectdTags: rCfg.ExtractCollectdTags,
-			},
-		},
+	rCfg, ok := cfg.(*Config)
+	if !ok {
+		return nil, fmt.Errorf("a wavefront receiver config was expected by the receiver factory, but got %T", rCfg)
 	}
-	return carbonreceiver.New(params, carbonCfg, consumer)
+	return newMetricsReceiver(rCfg, params, consumer), nil
 }

receiver/wavefrontreceiver/receiver.go

@@ -0,0 +1,72 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package wavefrontreceiver // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/wavefrontreceiver"
+
+import (
+	"context"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/config/confignet"
+	"go.opentelemetry.io/collector/consumer"
+	"go.opentelemetry.io/collector/receiver"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/carbonreceiver"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/carbonreceiver/protocol"
+)
+
+var _ receiver.Metrics = (*metricsReceiver)(nil)
+
+type metricsReceiver struct {
+	cfg            *Config
+	set            receiver.CreateSettings
+	nextConsumer   consumer.Metrics
+	carbonReceiver receiver.Metrics
+}
+
+func newMetricsReceiver(cfg *Config, set receiver.CreateSettings, nextConsumer consumer.Metrics) *metricsReceiver {
+	return &metricsReceiver{
+		cfg:          cfg,
+		set:          set,
+		nextConsumer: nextConsumer,
+	}
+}
+
+func (r *metricsReceiver) Start(ctx context.Context, host component.Host) error {
+	fact := carbonreceiver.NewFactory()
+
+	// Wavefront is very similar to Carbon: it is TCP based in which each received
+	// text line represents a single metric data point. They differ on the format
+	// of their textual representation.
+	//
+	// The Wavefront receiver leverages the Carbon receiver code by implementing
+	// a dedicated parser for its format.
+	carbonCfg := &carbonreceiver.Config{
+		NetAddr: confignet.NetAddr{
+			Endpoint:  r.cfg.Endpoint,
+			Transport: "tcp",
+		},
+		TCPIdleTimeout: r.cfg.TCPIdleTimeout,
+		Parser: &protocol.Config{
+			Type: "plaintext", // TODO: update after other parsers are implemented for Carbon receiver.
+			Config: &WavefrontParser{
+				ExtractCollectdTags: r.cfg.ExtractCollectdTags,
+			},
+		},
+	}
+
+	carbonReceiver, err := fact.CreateMetricsReceiver(ctx, r.set, carbonCfg, r.nextConsumer)
+	if err != nil {
+		return err
+	}
+	r.carbonReceiver = carbonReceiver
+
+	return r.carbonReceiver.Start(ctx, host)
+}
+
+func (r *metricsReceiver) Shutdown(ctx context.Context) error {
+	if r.carbonReceiver != nil {
+		return r.carbonReceiver.Shutdown(ctx)
+	}
+	return nil
+}