[receiver/hostmetrics] Add system.memory.limit metric (open-telemetry…

…#30306)

Adds opt-in support for `system.memory.limit`, standardized on
open-telemetry/semantic-conventions/pull/409.

.chloggen/mx-psi_system.memory.limit.yaml

@@ -0,0 +1,28 @@
+# 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: hostmetricsreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Add `system.memory.limit` metric reporting the total memory available."
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [30306]
+
+# (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 is opt-in. To enable it, set `scrapers::memory::metrics::system.memory.limit::enabled` to `true` in the hostmetrics config.
+
+# 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/hostmetricsreceiver/internal/scraper/memoryscraper/documentation.md

@@ -46,6 +46,14 @@ An estimate of how much memory is available for starting new applications, witho
 | ---- | ----------- | ---------- | ----------------------- | --------- |
 | By | Sum | Int | Cumulative | false |
 
+### system.memory.limit
+
+Total bytes of memory available.
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic |
+| ---- | ----------- | ---------- | ----------------------- | --------- |
+| By | Sum | Int | Cumulative | false |
+
 ### system.memory.utilization
 
 Percentage of memory bytes in use.

receiver/hostmetricsreceiver/internal/scraper/memoryscraper/internal/metadata/testdata/config.yaml

@@ -3,6 +3,8 @@ all_set:
   metrics:
     system.linux.memory.available:
       enabled: true
+    system.memory.limit:
+      enabled: true
     system.memory.usage:
       enabled: true
     system.memory.utilization:
@@ -11,6 +13,8 @@ none_set:
   metrics:
     system.linux.memory.available:
       enabled: false
+    system.memory.limit:
+      enabled: false
     system.memory.usage:
       enabled: false
     system.memory.utilization:

receiver/hostmetricsreceiver/internal/scraper/memoryscraper/memory_scraper.go

@@ -53,6 +53,10 @@ func (s *scraper) start(ctx context.Context, _ component.Host) error {
 	return nil
 }
 
+func (s *scraper) recordMemoryLimitMetric(now pcommon.Timestamp, memInfo *mem.VirtualMemoryStat) {
+	s.mb.RecordSystemMemoryLimitDataPoint(now, int64(memInfo.Total))
+}
+
 func (s *scraper) scrape(ctx context.Context) (pmetric.Metrics, error) {
 	ctx = context.WithValue(ctx, common.EnvKey, s.envMap)
 
@@ -69,6 +73,7 @@ func (s *scraper) scrape(ctx context.Context) (pmetric.Metrics, error) {
 				memInfo.Total), metricsLen)
 		}
 		s.recordMemoryUtilizationMetric(now, memInfo)
+		s.recordMemoryLimitMetric(now, memInfo)
 		s.recordSystemSpecificMetrics(now, memInfo)
 	}
 

receiver/hostmetricsreceiver/internal/scraper/memoryscraper/metadata.yaml

@@ -11,6 +11,15 @@ attributes:
     enum: [buffered, cached, inactive, free, slab_reclaimable, slab_unreclaimable, used]
 
 metrics:
+  system.memory.limit:
+    enabled: false
+    description: Total bytes of memory available.
+    unit: By
+    sum:
+      value_type: int
+      aggregation_temporality: cumulative
+      monotonic: false
+
   system.memory.usage:
     enabled: true
     description: Bytes of memory in use.