[receiver/sqlserver] Emit another metric for direct connection (open-telemetry#39940)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
Before this PR the `sqlserver.page.life_expectancy` metric was only
available when running on Windows as it was scraped from perf counters
directly. This change enables the metric to be emitted also from
directly connecting to SQL Server instances.

<!--Describe what testing was performed and which tests were added.-->
#### Testing
Updated existing testing.
open-telemetry#39930
adds this metric in the `configureAllScraperMetrics`, otherwise it would
have needed to be added here.

<!--Describe the documentation added.-->
#### Documentation
Removed documentation note that this metric was only available on
Windows.

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

Author: crobert-1

.chloggen/sqlserver_page_life_expectancy.yaml

@@ -0,0 +1,31 @@
+# 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: receiver/sqlserver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Enable `sqlserver.page.life_expectancy` metric for all configurations
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [39940]
+
+# (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: |
+  This metric was originally only available when running on Windows, but is
+  now available for all configuration options, including direct connection.
+  Since this metric is enabled by default, users who have direct connection
+  configured will now have this metric emitted by default.
+
+# 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/sqlserverreceiver/documentation.md

@@ -86,8 +86,6 @@ This metric is only available when running on Windows.
 
 Time a page will stay in the buffer pool.
 
-This metric is only available when running on Windows.
-
 | Unit | Metric Type | Value Type |
 | ---- | ----------- | ---------- |
 | s | Gauge | Int |

receiver/sqlserverreceiver/metadata.yaml

@@ -210,7 +210,6 @@ metrics:
     unit: s
     gauge:
       value_type: int
-    extended_documentation: This metric is only available when running on Windows.
   sqlserver.page.split.rate:
     enabled: true
     description: Number of pages split as a result of overflowing index pages.

receiver/sqlserverreceiver/scraper.go

@@ -235,6 +235,7 @@ func (s *sqlServerScraperHelper) recordDatabasePerfCounterMetrics(ctx context.Co
 	const numberOfDeadlocksPerSec = "Number of Deadlocks/sec"
 	const mirrorWritesTransactionPerSec = "Mirrored Write Transactions/sec"
 	const memoryGrantsPending = "Memory Grants Pending"
+	const pageLifeExpectancy = "Page life expectancy"
 	const pageLookupsPerSec = "Page lookups/sec"
 	const processesBlocked = "Processes blocked"
 	const sqlCompilationRate = "SQL Compilations/sec"
@@ -435,6 +436,14 @@ func (s *sqlServerScraperHelper) recordDatabasePerfCounterMetrics(ctx context.Co
 			} else {
 				s.mb.RecordSqlserverDeadlockRateDataPoint(now, val.(float64))
 			}
+		case pageLifeExpectancy:
+			val, err := retrieveInt(row, valueKey)
+			if err != nil {
+				err = fmt.Errorf("failed to parse valueKey for row %d: %w in %s", i, err, pageLifeExpectancy)
+				errs = append(errs, err)
+			} else {
+				s.mb.RecordSqlserverPageLifeExpectancyDataPoint(now, val.(int64))
+			}
 		case pageLookupsPerSec:
 			val, err := retrieveFloat(row, valueKey)
 			if err != nil {

receiver/sqlserverreceiver/testdata/expectedPerfCounters.yaml

@@ -151,6 +151,30 @@ resourceMetrics:
         scope:
           name: github.com/open-telemetry/opentelemetry-collector-contrib/receiver/sqlserverreceiver
           version: latest
+  - resource:
+      attributes:
+        - key: server.address
+          value:
+            stringValue: 0.0.0.0
+        - key: server.port
+          value:
+            intValue: "1433"
+        - key: sqlserver.instance.name
+          value:
+            stringValue: d26d40521426
+    scopeMetrics:
+      - metrics:
+          - description: Time a page will stay in the buffer pool.
+            gauge:
+              dataPoints:
+                - asInt: "16771"
+                  startTimeUnixNano: "1000000"
+                  timeUnixNano: "2000000"
+            name: sqlserver.page.life_expectancy
+            unit: s
+        scope:
+          name: github.com/open-telemetry/opentelemetry-collector-contrib/receiver/sqlserverreceiver
+          version: latest
   - resource:
       attributes:
         - key: server.address
@@ -175,6 +199,30 @@ resourceMetrics:
         scope:
           name: github.com/open-telemetry/opentelemetry-collector-contrib/receiver/sqlserverreceiver
           version: latest
+  - resource:
+      attributes:
+        - key: server.address
+          value:
+            stringValue: 0.0.0.0
+        - key: server.port
+          value:
+            intValue: "1433"
+        - key: sqlserver.instance.name
+          value:
+            stringValue: d26d40521426
+    scopeMetrics:
+      - metrics:
+          - description: Time a page will stay in the buffer pool.
+            gauge:
+              dataPoints:
+                - asInt: "16771"
+                  startTimeUnixNano: "1000000"
+                  timeUnixNano: "2000000"
+            name: sqlserver.page.life_expectancy
+            unit: s
+        scope:
+          name: github.com/open-telemetry/opentelemetry-collector-contrib/receiver/sqlserverreceiver
+          version: latest
   - resource:
       attributes:
         - key: server.address