util: Add idle timeout for scrape connections

retrieval/scrape.go

@@ -420,6 +420,7 @@ func (s *targetScraper) scrape(ctx context.Context, w io.Writer) error {
 
 		s.req = req
 	}
+
 	resp, err := ctxhttp.Do(ctx, s.client, s.req)
 	if err != nil {
 		return err

util/httputil/client.go

@@ -47,6 +47,9 @@ func NewClientFromConfig(cfg config.HTTPClientConfig) (*http.Client, error) {
 		DisableKeepAlives:  false,
 		TLSClientConfig:    tlsConfig,
 		DisableCompression: true,
+		// 5 minutes is typically above the maximum sane scrape interval. So we can
+		// use keepalive for all configurations.
+		IdleConnTimeout: 5 * time.Minute,
 	}
 
 	// If a bearer token is provided, create a round tripper that will set the