[hostmetricsreceiver] add system uptime metric (open-telemetry#35954)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
Add new uptime scraper to emit the `system.uptime` metric

<!-- Issue number (e.g. open-telemetry#1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes open-telemetry#31627 

<!--Describe what testing was performed and which tests were added.-->
#### Testing
Unit test added. Also tested locally (Linux VM) with following config:
```yaml
receivers:
  hostmetrics:
    scrapers:
      uptime:
exporters:
  debug:
    verbosity: detailed
service:
  pipelines:
    metrics:
      receivers:
        - hostmetrics
      exporters:
        - debug
```
<details><summary>Details</summary>
<p>

```console
$ make genotelcontribcol
[...]

$ make RUN_CONFIG=config-uptime.yaml run
2024-10-23T13:24:48.195+0200    info    [email protected]/service.go:135 Setting up own telemetry...
2024-10-23T13:24:48.195+0200    info    telemetry/metrics.go:70 Serving metrics {"address": "localhost:8888", "metrics level": "Normal"}
2024-10-23T13:24:48.195+0200    info    builders/builders.go:26 Development component. May change in the future.        {"kind": "exporter", "data_type": "metrics", "name": "debug"}
2024-10-23T13:24:48.199+0200    info    [email protected]/service.go:207 Starting otelcontribcol...      {"Version": "0.112.0-dev", "NumCPU": 7}
2024-10-23T13:24:48.199+0200    info    extensions/extensions.go:39     Starting extensions...
2024-10-23T13:24:48.199+0200    info    [email protected]/service.go:230 Everything is ready. Begin running and processing data.
2024-10-23T13:24:49.202+0200    info    Metrics {"kind": "exporter", "data_type": "metrics", "name": "debug", "resource metrics": 1, "metrics": 1, "data points": 1}
2024-10-23T13:24:49.202+0200    info    ResourceMetrics #0
Resource SchemaURL: https://opentelemetry.io/schemas/1.9.0
ScopeMetrics #0
ScopeMetrics SchemaURL: 
InstrumentationScope github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper 0.112.0-dev
Metric #0
Descriptor:
     -> Name: system.uptime
     -> Description: The time the system has been running
     -> Unit: s
     -> DataType: Sum
     -> IsMonotonic: false
     -> AggregationTemporality: Cumulative
NumberDataPoints #0
StartTimestamp: 2024-10-22 18:23:22 +0000 UTC
Timestamp: 2024-10-23 11:24:49.202512199 +0000 UTC
Value: 61287.000000
        {"kind": "exporter", "data_type": "metrics", "name": "debug"}
2024-10-23T13:25:49.206+0200    info    Metrics {"kind": "exporter", "data_type": "metrics", "name": "debug", "resource metrics": 1, "metrics": 1, "data points": 1}
2024-10-23T13:25:49.206+0200    info    ResourceMetrics #0
Resource SchemaURL: https://opentelemetry.io/schemas/1.9.0
ScopeMetrics #0
ScopeMetrics SchemaURL: 
InstrumentationScope github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper 0.112.0-dev
Metric #0
Descriptor:
     -> Name: system.uptime
     -> Description: The time the system has been running
     -> Unit: s
     -> DataType: Sum
     -> IsMonotonic: false
     -> AggregationTemporality: Cumulative
NumberDataPoints #0
StartTimestamp: 2024-10-22 18:23:22 +0000 UTC
Timestamp: 2024-10-23 11:25:49.206657828 +0000 UTC
Value: 61347.000000
        {"kind": "exporter", "data_type": "metrics", "name": "debug"}
2024-10-23T13:26:49.205+0200    info    Metrics {"kind": "exporter", "data_type": "metrics", "name": "debug", "resource metrics": 1, "metrics": 1, "data points": 1}
2024-10-23T13:26:49.205+0200    info    ResourceMetrics #0
Resource SchemaURL: https://opentelemetry.io/schemas/1.9.0
ScopeMetrics #0
ScopeMetrics SchemaURL: 
InstrumentationScope github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper 0.112.0-dev
Metric #0
Descriptor:
     -> Name: system.uptime
     -> Description: The time the system has been running
     -> Unit: s
     -> DataType: Sum
     -> IsMonotonic: false
     -> AggregationTemporality: Cumulative
NumberDataPoints #0
StartTimestamp: 2024-10-22 18:23:22 +0000 UTC
Timestamp: 2024-10-23 11:26:49.2051249 +0000 UTC
Value: 61407.000000
        {"kind": "exporter", "data_type": "metrics", "name": "debug"}
2024-10-23T13:27:49.210+0200    info    Metrics {"kind": "exporter", "data_type": "metrics", "name": "debug", "resource metrics": 1, "metrics": 1, "data points": 1}
2024-10-23T13:27:49.210+0200    info    ResourceMetrics #0
Resource SchemaURL: https://opentelemetry.io/schemas/1.9.0
ScopeMetrics #0
ScopeMetrics SchemaURL: 
InstrumentationScope github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper 0.112.0-dev
Metric #0
Descriptor:
     -> Name: system.uptime
     -> Description: The time the system has been running
     -> Unit: s
     -> DataType: Sum
     -> IsMonotonic: false
     -> AggregationTemporality: Cumulative
NumberDataPoints #0
StartTimestamp: 2024-10-22 18:23:22 +0000 UTC
Timestamp: 2024-10-23 11:27:49.21007371 +0000 UTC
Value: 61467.000000
        {"kind": "exporter", "data_type": "metrics", "name": "debug"}
^C
2024-10-23T13:27:54.204+0200  info    [email protected]/collector.go:328       Received signal from OS {"signal": "interrupt"}
2024-10-23T13:27:54.204+0200    info    [email protected]/service.go:266 Starting shutdown...
2024-10-23T13:27:54.204+0200    info    extensions/extensions.go:66     Stopping extensions...
2024-10-23T13:27:54.204+0200    info    [email protected]/service.go:280 Shutdown complete.
```

</p>
</details> 


<!--Describe the documentation added.-->
#### Documentation
Updated readme & generated scraper docs

<!--Please delete paragraphs that you did not use before submitting.-->

.chloggen/add-hostmetric-system-uptime.yaml

@@ -0,0 +1,25 @@
+# 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: hostmetricsreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add an uptime scraper in the hostmetrics receiver
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [31627]
+
+# (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]

receiver/hostmetricsreceiver/README.md

@@ -49,6 +49,7 @@ The available scrapers are:
 | [paging]     | All                          | Paging/Swap space utilization and I/O metrics          |
 | [processes]  | Linux, Mac                   | Process count metrics                                  |
 | [process]    | Linux, Windows, Mac          | Per process CPU, Memory, and Disk I/O metrics          |
+| [uptime]     | Linux, Windows, Mac          | Uptime metric                                          |
 
 [cpu]: ./internal/scraper/cpuscraper/documentation.md
 [disk]: ./internal/scraper/diskscraper/documentation.md
@@ -59,6 +60,7 @@ The available scrapers are:
 [paging]: ./internal/scraper/pagingscraper/documentation.md
 [processes]: ./internal/scraper/processesscraper/documentation.md
 [process]: ./internal/scraper/processscraper/documentation.md
+[uptime]: ./internal/scraper/uptimescraper/documentation.md
 
 ### Notes
 

receiver/hostmetricsreceiver/config_test.go

@@ -27,6 +27,7 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/pagingscraper"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/processesscraper"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/processscraper"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper"
 )
 
 func TestLoadConfig(t *testing.T) {
@@ -118,6 +119,11 @@ func TestLoadConfig(t *testing.T) {
 				cfg.SetEnvMap(common.EnvMap{})
 				return cfg
 			})(),
+			uptimescraper.TypeStr: (func() internal.Config {
+				cfg := (&uptimescraper.Factory{}).CreateDefaultConfig()
+				cfg.SetEnvMap(common.EnvMap{})
+				return cfg
+			})(),
 		},
 	}
 

receiver/hostmetricsreceiver/example_config.yaml

@@ -14,6 +14,7 @@ receivers:
       network:
       paging:
       processes:
+      uptime:
 
 exporters:
   debug:

receiver/hostmetricsreceiver/factory.go

@@ -27,6 +27,7 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/pagingscraper"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/processesscraper"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/processscraper"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper"
 )
 
 const (
@@ -45,6 +46,7 @@ var (
 		pagingscraper.TypeStr:     &pagingscraper.Factory{},
 		processesscraper.TypeStr:  &processesscraper.Factory{},
 		processscraper.TypeStr:    &processscraper.Factory{},
+		uptimescraper.TypeStr:     &uptimescraper.Factory{},
 	}
 )
 

receiver/hostmetricsreceiver/hostmetrics_receiver_test.go

@@ -34,6 +34,7 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/pagingscraper"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/processesscraper"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/processscraper"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper"
 )
 
 var allMetrics = []string{
@@ -81,6 +82,7 @@ var factories = map[string]internal.ScraperFactory{
 	pagingscraper.TypeStr:     &pagingscraper.Factory{},
 	processesscraper.TypeStr:  &processesscraper.Factory{},
 	processscraper.TypeStr:    &processscraper.Factory{},
+	uptimescraper.TypeStr:     &uptimescraper.Factory{},
 }
 
 type testEnv struct {
@@ -395,6 +397,19 @@ func Benchmark_ScrapeProcessMetrics(b *testing.B) {
 	benchmarkScrapeMetrics(b, cfg)
 }
 
+func Benchmark_ScrapeUptimeMetrics(b *testing.B) {
+	if runtime.GOOS != "linux" && runtime.GOOS != "windows" {
+		b.Skip("skipping test on non linux/windows")
+	}
+
+	cfg := &Config{
+		ControllerConfig: scraperhelper.NewDefaultControllerConfig(),
+		Scrapers:         map[string]internal.Config{uptimescraper.TypeStr: (&uptimescraper.Factory{}).CreateDefaultConfig()},
+	}
+
+	benchmarkScrapeMetrics(b, cfg)
+}
+
 func Benchmark_ScrapeSystemMetrics(b *testing.B) {
 	cfg := &Config{
 		ControllerConfig: scraperhelper.NewDefaultControllerConfig(),

receiver/hostmetricsreceiver/internal/scraper/uptimescraper/config.go

@@ -0,0 +1,16 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package uptimescraper // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper"
+
+import (
+	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper/internal/metadata"
+)
+
+// Config relating to Uptime Metric Scraper.
+type Config struct {
+	// MetricsBuilderConfig allows to customize scraped metrics/attributes representation.
+	metadata.MetricsBuilderConfig `mapstructure:",squash"`
+	internal.ScraperConfig
+}

receiver/hostmetricsreceiver/internal/scraper/uptimescraper/doc.go

@@ -0,0 +1,6 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+//go:generate mdatagen metadata.yaml
+
+package uptimescraper // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper"

receiver/hostmetricsreceiver/internal/scraper/uptimescraper/documentation.md

@@ -0,0 +1,23 @@
+[comment]: <> (Code generated by mdatagen. DO NOT EDIT.)
+
+# hostmetricsreceiver/uptime
+
+**Parent Component:** hostmetrics
+
+## Default Metrics
+
+The following metrics are emitted by default. Each of them can be disabled by applying the following configuration:
+
+```yaml
+metrics:
+  <metric_name>:
+    enabled: false
+```
+
+### system.uptime
+
+The time the system has been running
+
+| Unit | Metric Type | Value Type |
+| ---- | ----------- | ---------- |
+| s | Gauge | Double |

receiver/hostmetricsreceiver/internal/scraper/uptimescraper/factory.go

@@ -0,0 +1,54 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package uptimescraper // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper"
+
+import (
+	"context"
+	"errors"
+	"runtime"
+
+	"go.opentelemetry.io/collector/receiver"
+	"go.opentelemetry.io/collector/receiver/scraperhelper"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal"
+	hostmeta "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/metadata"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/uptimescraper/internal/metadata"
+)
+
+// This file implements Factory for Uptime scraper.
+
+const (
+	// TypeStr the value of "type" key in configuration.
+	TypeStr = "uptime"
+)
+
+// Factory is the Factory for scraper.
+type Factory struct {
+}
+
+// CreateDefaultConfig creates the default configuration for the Scraper.
+func (f *Factory) CreateDefaultConfig() internal.Config {
+	return &Config{
+		MetricsBuilderConfig: metadata.DefaultMetricsBuilderConfig(),
+	}
+}
+
+// CreateMetricsScraper creates a resource scraper based on provided config.
+func (f *Factory) CreateMetricsScraper(
+	ctx context.Context,
+	settings receiver.Settings,
+	cfg internal.Config,
+) (scraperhelper.Scraper, error) {
+	if runtime.GOOS != "linux" && runtime.GOOS != "windows" && runtime.GOOS != "darwin" {
+		return nil, errors.New("uptime scraper only available on Linux, Windows, or MacOS")
+	}
+
+	uptimeScraper := newUptimeScraper(ctx, settings, cfg.(*Config))
+
+	return scraperhelper.NewScraper(
+		hostmeta.Type,
+		uptimeScraper.scrape,
+		scraperhelper.WithStart(uptimeScraper.start),
+	)
+}