[receiver/ntpreceiver] fix ntp.host was not being emitted (open-telemetry#43132)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

This PR fixes the `ntp.host` resource attribute was not being emitted
even though it was enabled by default.

I'm also proposing being an additional code owner for this component.

<!-- Issue number (e.g. open-telemetry#1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes open-telemetry#43129

<!--Describe what testing was performed and which tests were added.-->
#### Testing

I added new tests for `receiver.go`.

Also tested it locally with the same configuration shared on the issue.

```sh
2025-10-05T00:16:24.452+0100	info	[email protected]/service.go:222	Starting otelcontribcol...	{"resource": {"service.instance.id": "9202fda2-095d-4055-8412-dc4de4b8308d", "service.name": "otelcontribcol", "service.version": "0.136.0-dev"}, "Version": "0.136.0-dev", "NumCPU": 12}
2025-10-05T00:16:24.452+0100	info	extensions/extensions.go:41	Starting extensions...	{"resource": {"service.instance.id": "9202fda2-095d-4055-8412-dc4de4b8308d", "service.name": "otelcontribcol", "service.version": "0.136.0-dev"}}
2025-10-05T00:16:24.452+0100	info	[email protected]/service.go:245	Everything is ready. Begin running and processing data.	{"resource": {"service.instance.id": "9202fda2-095d-4055-8412-dc4de4b8308d", "service.name": "otelcontribcol", "service.version": "0.136.0-dev"}}
2025-10-05T00:16:25.658+0100	info	Metrics	{"resource": {"service.instance.id": "9202fda2-095d-4055-8412-dc4de4b8308d", "service.name": "otelcontribcol", "service.version": "0.136.0-dev"}, "otelcol.component.id": "debug", "otelcol.component.kind": "exporter", "otelcol.signal": "metrics", "resource metrics": 1, "metrics": 1, "data points": 1}
2025-10-05T00:16:25.659+0100	info	ResourceMetrics #0
Resource SchemaURL:
Resource attributes:
     -> ntp.host: Str(time.nist.gov:123)
ScopeMetrics #0
ScopeMetrics SchemaURL:
InstrumentationScope github.com/open-telemetry/opentelemetry-collector-contrib/receiver/ntpreceiver 0.136.0-dev
Metric #0
Descriptor:
     -> Name: ntp.offset
     -> Description: Time difference between local and NTP server clocks
     -> Unit: ns
     -> DataType: Gauge
NumberDataPoints #0
StartTimestamp: 2025-10-04 23:16:24.452351 +0000 UTC
Timestamp: 2025-10-04 23:16:25.647124 +0000 UTC
Value: 91327175
	{"resource": {"service.instance.id": "9202fda2-095d-4055-8412-dc4de4b8308d", "service.name": "otelcontribcol", "service.version": "0.136.0-dev"}, "otelcol.component.id": "debug", "otelcol.component.kind": "exporter", "otelcol.signal": "metrics"}
```

---------

Signed-off-by: Paulo Dias <[email protected]>

Author: paulojmdias

.chloggen/fix_43129.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: "bug_fix"
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: "ntpreceiver"
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Fix missing resource attribute 'ntp.host' to ntpreceiver metrics"
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [43129]
+
+# (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]

.github/CODEOWNERS

@@ -292,7 +292,7 @@ receiver/namedpipereceiver/                                      @open-telemetry
 receiver/netflowreceiver/                                        @open-telemetry/collector-contrib-approvers @evan-bradley @dlopes7
 receiver/nginxreceiver/                                          @open-telemetry/collector-contrib-approvers @colelaven @ishleenk17
 receiver/nsxtreceiver/                                           @open-telemetry/collector-contrib-approvers @dashpole @schmikei
-receiver/ntpreceiver/                                            @open-telemetry/collector-contrib-approvers @atoulme
+receiver/ntpreceiver/                                            @open-telemetry/collector-contrib-approvers @atoulme @paulojmdias
 receiver/oracledbreceiver/                                       @open-telemetry/collector-contrib-approvers @dmitryax @crobert-1 @atoulme
 receiver/osqueryreceiver/                                        @open-telemetry/collector-contrib-approvers @nslaughter @smithclay
 receiver/otelarrowreceiver/                                      @open-telemetry/collector-contrib-approvers @jmacd @moh-osman3

receiver/ntpreceiver/README.md

@@ -7,7 +7,7 @@
 | Distributions | [contrib] |
 | Issues        | [![Open issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aopen%20label%3Areceiver%2Fntp%20&label=open&color=orange&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aopen+is%3Aissue+label%3Areceiver%2Fntp) [![Closed issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aclosed%20label%3Areceiver%2Fntp%20&label=closed&color=blue&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aclosed+is%3Aissue+label%3Areceiver%2Fntp) |
 | Code coverage | [![codecov](https://codecov.io/github/open-telemetry/opentelemetry-collector-contrib/graph/main/badge.svg?component=receiver_ntp)](https://app.codecov.io/gh/open-telemetry/opentelemetry-collector-contrib/tree/main/?components%5B0%5D=receiver_ntp&displayType=list) |
-| [Code Owners](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CONTRIBUTING.md#becoming-a-code-owner)    | [@atoulme](https://www.github.com/atoulme) \| Seeking more code owners! |
+| [Code Owners](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CONTRIBUTING.md#becoming-a-code-owner)    | [@atoulme](https://www.github.com/atoulme), [@paulojmdias](https://www.github.com/paulojmdias) \| Seeking more code owners! |
 
 [beta]: https://github.com/open-telemetry/opentelemetry-collector/blob/main/docs/component-stability.md#beta
 [contrib]: https://github.com/open-telemetry/opentelemetry-collector-releases/tree/main/distributions/otelcol-contrib

receiver/ntpreceiver/metadata.yaml

@@ -6,7 +6,7 @@ status:
     beta: [metrics]
   distributions: [contrib]
   codeowners:
-    active: [atoulme]
+    active: [atoulme, paulojmdias]
     seeking_new: true
 
 resource_attributes:

receiver/ntpreceiver/receiver.go

@@ -16,6 +16,8 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/ntpreceiver/internal/metadata"
 )
 
+var queryWithOptions = ntp.QueryWithOptions
+
 type ntpScraper struct {
 	logger   *zap.Logger
 	mb       *metadata.MetricsBuilder
@@ -26,12 +28,16 @@ type ntpScraper struct {
 
 func (s *ntpScraper) scrape(context.Context) (pmetric.Metrics, error) {
 	options := ntp.QueryOptions{Version: s.version, Timeout: s.timeout}
-	response, err := ntp.QueryWithOptions(s.endpoint, options)
+	response, err := queryWithOptions(s.endpoint, options)
 	if err != nil {
-		return pmetric.Metrics{}, err
+		return pmetric.NewMetrics(), err
 	}
 	s.mb.RecordNtpOffsetDataPoint(pcommon.NewTimestampFromTime(time.Now()), response.ClockOffset.Nanoseconds())
-	s.mb.NewResourceBuilder().SetNtpHost(s.endpoint)
+
+	rb := s.mb.NewResourceBuilder()
+	rb.SetNtpHost(s.endpoint)
+
+	s.mb.EmitForResource(metadata.WithResource(rb.Emit()))
 	return s.mb.Emit(), nil
 }
 

receiver/ntpreceiver/receiver_test.go

@@ -0,0 +1,111 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package ntpreceiver
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/beevik/ntp"
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/pdata/pmetric"
+	"go.opentelemetry.io/collector/receiver/receivertest"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/ntpreceiver/internal/metadata"
+)
+
+// Minimal scraper builder for tests (no controller). We keep this close to prod.
+func newTestScraper(cfg *Config) *ntpScraper {
+	settings := receivertest.NewNopSettings(metadata.Type)
+	return &ntpScraper{
+		logger:   settings.Logger,
+		mb:       metadata.NewMetricsBuilder(cfg.MetricsBuilderConfig, settings),
+		version:  cfg.Version,
+		endpoint: cfg.Endpoint,
+		timeout:  5 * time.Second, // fixed timeout for tests
+	}
+}
+
+func TestScraper_Success(t *testing.T) {
+	// Mock NTP query
+	old := queryWithOptions
+	defer func() { queryWithOptions = old }()
+	queryWithOptions = func(_ string, _ ntp.QueryOptions) (*ntp.Response, error) {
+		// We return a non-zero offset; test will not assert the value to avoid controller-specific init.
+		return &ntp.Response{ClockOffset: 250 * time.Millisecond}, nil
+	}
+
+	cfg := createDefaultConfig().(*Config)
+	cfg.Endpoint = "time.example.com:123"
+
+	s := newTestScraper(cfg)
+	metrics, err := s.scrape(t.Context())
+	require.NoError(t, err)
+	require.NotNil(t, metrics)
+
+	// ResourceMetrics present
+	rmSlice := metrics.ResourceMetrics()
+	require.Equal(t, 1, rmSlice.Len())
+
+	// Resource attribute ntp.host set to endpoint
+	rm := rmSlice.At(0)
+	resAttrs := rm.Resource().Attributes()
+	val, ok := resAttrs.Get("ntp.host")
+	require.True(t, ok, "expected ntp.host resource attribute")
+	require.Equal(t, cfg.Endpoint, val.Str())
+
+	// One scope, one metric
+	smSlice := rm.ScopeMetrics()
+	require.Equal(t, 1, smSlice.Len())
+	mSlice := smSlice.At(0).Metrics()
+	require.Equal(t, 1, mSlice.Len())
+
+	m := mSlice.At(0)
+	require.Equal(t, "ntp.offset", m.Name())
+
+	// Unit should be "ns" per current receiver metadata (do not fail hard if empty, but assert when present)
+	if u := m.Unit(); u != "" {
+		require.Equal(t, "ns", u, "expected ntp.offset unit to be ns")
+	}
+
+	// Handle Gauge vs Sum defensively; generator may emit Gauge.
+	var dps pmetric.NumberDataPointSlice
+	switch m.Type() {
+	case pmetric.MetricTypeGauge:
+		dps = m.Gauge().DataPoints()
+	case pmetric.MetricTypeSum:
+		dps = m.Sum().DataPoints()
+	default:
+		t.Fatalf("unexpected metric type: %v", m.Type())
+	}
+
+	// Exactly one data point with non-zero timestamps
+	require.Equal(t, 1, dps.Len())
+	dp := dps.At(0)
+	require.NotZero(t, dp.Timestamp(), "datapoint must have a timestamp")
+	// StartTimestamp may be zero for Gauge; only assert when present
+	if st := dp.StartTimestamp(); st != 0 {
+		require.NotZero(t, st, "start timestamp should not be zero when set")
+	}
+}
+
+func TestScraper_Error(t *testing.T) {
+	// Mock failure
+	old := queryWithOptions
+	defer func() { queryWithOptions = old }()
+	queryWithOptions = func(_ string, _ ntp.QueryOptions) (*ntp.Response, error) {
+		return nil, errors.New("mock failure")
+	}
+
+	cfg := createDefaultConfig().(*Config)
+	cfg.Endpoint = "bad.host"
+
+	s := newTestScraper(cfg)
+	metrics, err := s.scrape(t.Context())
+
+	require.Error(t, err)
+	require.NotNil(t, metrics)
+	require.Equal(t, 0, metrics.ResourceMetrics().Len(), "expected no metrics on error")
+}