[receiver/apache] Add support for number of connections per async state metric (#42158)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
The PR adds changes to extract metrics pertaining to connections per
async state. See the related issue for more details.
<!-- Issue number (e.g. #1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Relates
#41886

<!--Describe what testing was performed and which tests were added.-->
#### Testing
Unit and integration tests for the scraper have been extended with data
for new metrics.

<!--Describe the documentation added.-->
#### Documentation
Documentation generated by mdatagen has been added.

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

---------

Co-authored-by: Antoine Toulme <[email protected]>

Author: devamanv

.chloggen/apache-req-connections-metrics.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: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: apachereceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add number of connections per async state metrics.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [41886]
+
+# (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/apachereceiver/documentation.md

@@ -12,6 +12,20 @@ metrics:
     enabled: false
 ```
 
+### apache.connections.async
+
+The number of connections in different asynchronous states reported by Apache's server-status.
+
+| Unit | Metric Type | Value Type |
+| ---- | ----------- | ---------- |
+| {connections} | Gauge | Int |
+
+#### Attributes
+
+| Name | Description | Values | Optional |
+| ---- | ----------- | ------ | -------- |
+| connection_state | The asynchronous connection state reported by Apache's server-status. | Str: ``writing``, ``keepalive``, ``closing`` | false |
+
 ### apache.cpu.load
 
 Current load of the CPU.

receiver/apachereceiver/internal/metadata/generated_config.go

@@ -1,6 +1,8 @@
 default:
 all_set:
   metrics:
+    apache.connections.async:
+      enabled: true
     apache.cpu.load:
       enabled: true
     apache.cpu.time:
@@ -32,6 +34,8 @@ all_set:
       enabled: true
 none_set:
   metrics:
+    apache.connections.async:
+      enabled: false
     apache.cpu.load:
       enabled: false
     apache.cpu.time:

receiver/apachereceiver/internal/metadata/generated_config_test.go

@@ -58,6 +58,13 @@ attributes:
       - finishing
       - idle_cleanup
       - unknown
+  connection_state:
+    description: The asynchronous connection state reported by Apache's server-status.
+    type: string
+    enum:
+      - writing
+      - keepalive
+      - closing
 
 metrics:
   apache.uptime:
@@ -174,3 +181,11 @@ metrics:
       monotonic: false
       aggregation_temporality: cumulative
     attributes: [scoreboard_state]
+  apache.connections.async:
+    enabled: true
+    description: The number of connections in different asynchronous states reported by Apache's server-status.
+    unit: "{connections}"
+    gauge:
+      value_type: int
+      input_type: string
+    attributes: [connection_state]

receiver/apachereceiver/internal/metadata/generated_metrics.go

@@ -76,6 +76,12 @@ func (r *apacheScraper) scrape(context.Context) (pmetric.Metrics, error) {
 			addPartialIfError(errs, r.mb.RecordApacheUptimeDataPoint(now, metricValue))
 		case "ConnsTotal":
 			addPartialIfError(errs, r.mb.RecordApacheCurrentConnectionsDataPoint(now, metricValue))
+		case "ConnsAsyncWriting":
+			addPartialIfError(errs, r.mb.RecordApacheConnectionsAsyncDataPoint(now, metricValue, metadata.AttributeConnectionStateWriting))
+		case "ConnsAsyncKeepAlive":
+			addPartialIfError(errs, r.mb.RecordApacheConnectionsAsyncDataPoint(now, metricValue, metadata.AttributeConnectionStateKeepalive))
+		case "ConnsAsyncClosing":
+			addPartialIfError(errs, r.mb.RecordApacheConnectionsAsyncDataPoint(now, metricValue, metadata.AttributeConnectionStateClosing))
 		case "BusyWorkers":
 			addPartialIfError(errs, r.mb.RecordApacheWorkersDataPoint(now, metricValue, metadata.AttributeWorkersStateBusy))
 		case "IdleWorkers":

receiver/apachereceiver/internal/metadata/generated_metrics_test.go

@@ -145,12 +145,18 @@ ReqPerSec: 719.771
 IdleWorkers: 227
 ConnsTotal: 110
 BytesPerSec: 73.12
+ConnsAsyncWriting: 2
+ConnsAsyncKeepAlive: 1
+ConnsAsyncClosing: 1
 		`
 		want := map[string]string{
-			"ReqPerSec":   "719.771",
-			"IdleWorkers": "227",
-			"ConnsTotal":  "110",
-			"BytesPerSec": "73.12",
+			"ReqPerSec":           "719.771",
+			"IdleWorkers":         "227",
+			"ConnsTotal":          "110",
+			"BytesPerSec":         "73.12",
+			"ConnsAsyncWriting":   "2",
+			"ConnsAsyncKeepAlive": "1",
+			"ConnsAsyncClosing":   "1",
 		}
 		require.Equal(t, want, parseStats(got))
 	})
@@ -185,6 +191,9 @@ CPULoad: 0.66
 Load1: 0.9
 Load5: 0.4
 Load15: 0.3
+ConnsAsyncWriting: 2
+ConnsAsyncKeepAlive: 1
+ConnsAsyncClosing: 1
 Total Duration: 1501
 Scoreboard: S_DD_L_GGG_____W__IIII_C________________W__________________________________.........................____WR______W____W________________________C______________________________________W_W____W______________R_________R________C_________WK_W________K_____W__C__________W___R______.............................................................................................................................
 `))