add cpu time information to the metrics endpoint

Author: leafo

zipserver/metrics.go

@@ -8,6 +8,7 @@ import (
 	"reflect"
 	"strings"
 	"sync/atomic"
+	"syscall"
 )
 
 var globalMetrics = &MetricsCounter{}
@@ -44,9 +45,24 @@ func (m *MetricsCounter) RenderMetrics(config *Config) string {
 
 	}
 
+	userCPU, systemCPU := getCPUTime()
+	metrics.WriteString(fmt.Sprintf("zipserver_cpu_user_seconds_total{host=\"%s\"} %f\n", hostname, userCPU))
+	metrics.WriteString(fmt.Sprintf("zipserver_cpu_system_seconds_total{host=\"%s\"} %f\n", hostname, systemCPU))
+
 	return metrics.String()
 }
 
+// getCPUTime returns the cumulative user and system CPU time for this process
+func getCPUTime() (userSeconds, systemSeconds float64) {
+	var rusage syscall.Rusage
+	if err := syscall.Getrusage(syscall.RUSAGE_SELF, &rusage); err != nil {
+		return 0, 0
+	}
+	userSeconds = float64(rusage.Utime.Sec) + float64(rusage.Utime.Usec)/1e6
+	systemSeconds = float64(rusage.Stime.Sec) + float64(rusage.Stime.Usec)/1e6
+	return
+}
+
 // wrap a reader to count bytes read into the counter
 func metricsReader(reader io.Reader, counter *atomic.Int64) readerClosure {
 	return func(p []byte) (int, error) {

zipserver/metrics_test.go

@@ -32,13 +32,18 @@ func Test_Metrics(t *testing.T) {
 		MetricsHost: "localhost",
 	}
 
-	expectedMetrics := `zipserver_requests_total{host="localhost"} 1
-zipserver_errors_total{host="localhost"} 0
-zipserver_extracted_files_total{host="localhost"} 1
-zipserver_copied_files_total{host="localhost"} 0
-zipserver_deleted_files_total{host="localhost"} 0
-zipserver_downloaded_bytes_total{host="localhost"} 7
-zipserver_uploaded_bytes_total{host="localhost"} 0
-`
-	assert.Equal(t, expectedMetrics, metrics.RenderMetrics(config))
+	rendered := metrics.RenderMetrics(config)
+
+	// Check counter metrics (exact values)
+	assert.Contains(t, rendered, `zipserver_requests_total{host="localhost"} 1`)
+	assert.Contains(t, rendered, `zipserver_errors_total{host="localhost"} 0`)
+	assert.Contains(t, rendered, `zipserver_extracted_files_total{host="localhost"} 1`)
+	assert.Contains(t, rendered, `zipserver_copied_files_total{host="localhost"} 0`)
+	assert.Contains(t, rendered, `zipserver_deleted_files_total{host="localhost"} 0`)
+	assert.Contains(t, rendered, `zipserver_downloaded_bytes_total{host="localhost"} 7`)
+	assert.Contains(t, rendered, `zipserver_uploaded_bytes_total{host="localhost"} 0`)
+
+	// Check CPU metrics are present (values vary per run)
+	assert.Contains(t, rendered, `zipserver_cpu_user_seconds_total{host="localhost"}`)
+	assert.Contains(t, rendered, `zipserver_cpu_system_seconds_total{host="localhost"}`)
 }