collector: add pprof labels to build and collection (#2562)

Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>

README.md

@@ -210,6 +210,9 @@ windows_exporter provides the following HTTP endpoints:
 * `/health`: Returns 200 OK when the exporter is running.
 * `/debug/pprof/`: Exposes the [pprof](https://golang.org/pkg/net/http/pprof/) endpoints. Only, if `--debug.enabled` is set.
 
+CPU and goroutine profiles include a `collector` label with the collector name, so profiles can be filtered by collector.
+Workers started during collector initialization inherit this label.
+
 ### Using [defaults] with `--collectors.enabled` argument
 
 Using `[defaults]`  with `--collectors.enabled` argument which gets expanded with all default collectors.

pkg/collector/collect.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"log/slog"
 	"runtime/debug"
+	"runtime/pprof"
 	"sync"
 	"time"
 
@@ -85,10 +86,12 @@ func (c *Collection) collectAll(ctx context.Context, ch chan<- prometheus.Metric
 	// timeout handling is done in the execute function
 	for name, metricsCollector := range c.collectors {
 		wg.Go(func() {
-			collectorStatusCh <- collectorStatus{
-				name:       name,
-				statusCode: c.collectCollector(ctx, ch, logger, name, metricsCollector),
-			}
+			pprof.Do(ctx, pprof.Labels("collector", name), func(ctx context.Context) {
+				collectorStatusCh <- collectorStatus{
+					name:       name,
+					statusCode: c.collectCollector(ctx, ch, logger, name, metricsCollector),
+				}
+			})
 		})
 	}
 

pkg/collector/collection.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"log/slog"
 	"maps"
+	"runtime/pprof"
 	"slices"
 	gotime "time"
 
@@ -248,10 +249,13 @@ func (c *Collection) Build(ctx context.Context, logger *slog.Logger) error {
 		state := c.state.collector(name)
 
 		go func() {
-			resultCh <- buildResult{
-				name: collector.GetName(),
-				err:  state.build(ctx, logger, miSession, collector),
-			}
+			// Workers started by Build inherit the collector's profiling label.
+			pprof.Do(ctx, pprof.Labels("collector", name), func(ctx context.Context) {
+				resultCh <- buildResult{
+					name: collector.GetName(),
+					err:  state.build(ctx, logger, miSession, collector),
+				}
+			})
 		}()
 	}