feat(host_metrics): expose number of oom_kill events

changelog.d/host_metrics_oom_kill.feature.md

@@ -0,0 +1,4 @@
+The `host_metrics` source now exposes an `oom_kill` counter metric on Linux,
+reporting the number of Out-Of-Memory kill events recorded by the kernel.
+
+authors: simonhammes

src/sources/host_metrics/memory.rs

@@ -10,6 +10,9 @@ use vector_lib::event::MetricTags;
 use super::HostMetrics;
 use crate::internal_events::HostMetricsScrapeDetailError;
 
+#[cfg(target_os = "linux")]
+const OOM_KILL: &str = "oom_kill";
+
 impl HostMetrics {
     pub async fn memory_metrics(&self, output: &mut super::MetricsBuffer) {
         output.name = "memory";
@@ -122,4 +125,62 @@ impl HostMetrics {
             }
         }
     }
+
+    #[cfg(target_os = "linux")]
+    pub async fn vmstat_metrics(&self, output: &mut super::MetricsBuffer) {
+        output.name = "memory";
+
+        // Spawn blocking task to avoid blocking the async runtime with synchronous I/O
+        let result = tokio::task::spawn_blocking(procfs::vmstat)
+            .await
+            .unwrap_or_else(|join_error| {
+                Err(procfs::ProcError::Other(format!(
+                    "Failed to join blocking task: {}",
+                    join_error
+                )))
+            });
+
+        match result {
+            Ok(stats) => {
+                if let Some(&oom_kill) = stats.get("oom_kill") {
+                    output.counter(OOM_KILL, oom_kill as f64, MetricTags::default());
+                }
+            }
+            Err(error) => {
+                emit!(HostMetricsScrapeDetailError {
+                    message: "Failed to load vmstat info.",
+                    error,
+                });
+            }
+        }
+    }
+}
+
+#[cfg(all(test, target_os = "linux"))]
+mod tests {
+    use crate::event::metric::MetricValue;
+    use crate::sources::host_metrics::{HostMetrics, HostMetricsConfig, MetricsBuffer};
+
+    use super::OOM_KILL;
+
+    #[tokio::test]
+    async fn generates_vmstat_oom_kill_metric() {
+        let mut buffer = MetricsBuffer::new(None);
+        HostMetrics::new(HostMetricsConfig::default())
+            .vmstat_metrics(&mut buffer)
+            .await;
+        let metrics = buffer.metrics;
+
+        assert_eq!(metrics.len(), 1);
+
+        let metric = &metrics[0];
+        assert_eq!(metric.name(), OOM_KILL);
+        assert!(
+            matches!(metric.value(), MetricValue::Counter { .. }),
+            "oom_kill metric should be a counter"
+        );
+
+        let tags = metric.tags().expect("metric must have tags");
+        assert_eq!(tags.get("collector"), Some("memory"));
+    }
 }

src/sources/host_metrics/mod.rs

@@ -423,6 +423,8 @@ impl HostMetrics {
         if self.config.has_collector(Collector::Memory) {
             self.memory_metrics(&mut buffer).await;
             self.swap_metrics(&mut buffer).await;
+            #[cfg(target_os = "linux")]
+            self.vmstat_metrics(&mut buffer).await;
         }
         if self.config.has_collector(Collector::Network) {
             self.network_metrics(&mut buffer).await;

website/cue/reference/components/sources/host_metrics.cue

@@ -166,6 +166,7 @@ components: sources: host_metrics: {
 		memory_total_bytes: _host & _memory_gauge & {description: "The total number of bytes of main memory."}
 		memory_used_bytes: _host & _memory_linux & {description: "The number of bytes of main memory used by programs or caches."}
 		memory_wired_bytes: _host & _memory_macos & {description: "The number of wired bytes of main memory."}
+		oom_kill: _host & _memory_counter & _linux & {description: "The number of Out-Of-Memory (OOM) kill events recorded."}
 
 		// Host network
 		network_receive_bytes_total: _host & _network_counter & {description: "The number of bytes received on this interface."}
@@ -177,15 +178,15 @@ components: sources: host_metrics: {
 		network_transmit_packets_total: _host & _network_nomac & {description: "The number of packets transmitted on this interface."}
 
 		// Host tcp
-		tcp_connections_total: _host & _tcp_linux & _tcp_gauge & {description: "The number of TCP connections."}
-		tcp_tx_queued_bytes_total: _host & _tcp_linux & {
+		tcp_connections_total: _host & _linux & _tcp_gauge & {description: "The number of TCP connections."}
+		tcp_tx_queued_bytes_total: _host & _linux & {
 			description: "The number of bytes in the send queue across all connections."
 			type:        "gauge"
 			tags: _host_metrics_tags & {
 				collector: examples: ["tcp"]
 			}
 		}
-		tcp_rx_queued_bytes_total: _host & _tcp_linux & {
+		tcp_rx_queued_bytes_total: _host & _linux & {
 			description: "The number of bytes in the receive queue across all connections."
 			type:        "gauge"
 			tags: _host_metrics_tags & {
@@ -300,7 +301,7 @@ components: sources: host_metrics: {
 			}
 		}
 
-		_tcp_linux: {relevant_when: "OS is Linux"}
+		_linux: {relevant_when: "OS is Linux"}
 		_tcp_gauge: {
 			type: "gauge"
 			tags: _host_metrics_tags & {