lib/promscrape/discovery: close unused HTTP connections to service discovery servers

This should prevent from connection leaks

See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4724

app/vmagent/remotewrite/remotewrite.go

@@ -526,8 +526,8 @@ func newRemoteWriteCtx(argIdx int, at *auth.Token, remoteWriteURL *url.URL, maxI
 func (rwctx *remoteWriteCtx) MustStop() {
 	// sas must be stopped before rwctx is closed
 	// because sas can write pending series to rwctx.pss if there are any
-	sas := rwctx.sas.Swap(nil)
-	sas.MustStop()
+	rwctx.sas.MustStop()
+	rwctx.sas = nil
 
 	for _, ps := range rwctx.pss {
 		ps.MustStop()

docs/CHANGELOG.md

@@ -19,6 +19,7 @@ The following tip changes can be tested by building VictoriaMetrics components f
 * SECURITY: upgrade base docker image (Alpine) from 3.18.2 to 3.18.3. See [alpine 3.18.3 release notes](https://alpinelinux.org/posts/Alpine-3.15.10-3.16.7-3.17.5-3.18.3-released.html).
 
 * BUGFIX: vminsert: fixed decoding of label values with slash when accepting data via [pushgateway protocol](https://docs.victoriametrics.com/#how-to-import-data-in-prometheus-exposition-format). This fixes Prometheus golang client compatibility. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4692).
+* BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): close HTTP connections to [service discovery](https://docs.victoriametrics.com/sd_configs.html) servers when they are no longer needed. This should prevent from possible connection exhasution in some cases. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4724).
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): properly apply `if` filters during [relabeling](https://docs.victoriametrics.com/vmagent.html#relabeling-enhancements). Previously the `if` filter could improperly work. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4806) and [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/4816).
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): fix possible panic at shutdown when [stream aggregation](https://docs.victoriametrics.com/stream-aggregation.html) is enabled. See [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/4407) for details.
 * BUGFIX: [vmauth](https://docs.victoriametrics.com/vmauth.html): Properly handle LOCAL command for proxy protocol. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3335#issuecomment-1569864108).

lib/promscrape/discovery/azure/azure.go

@@ -58,7 +58,11 @@ func (sdc *SDConfig) GetLabels(baseDir string) ([]*promutils.Labels, error) {
 
 // MustStop stops further usage for sdc.
 func (sdc *SDConfig) MustStop() {
-	configMap.Delete(sdc)
+	v := configMap.Delete(sdc)
+	if v != nil {
+		cfg := v.(*apiConfig)
+		cfg.c.Stop()
+	}
 }
 
 func appendMachineLabels(vms []virtualMachine, port int, sdc *SDConfig) []*promutils.Labels {

lib/promscrape/discovery/azure/machine_test.go

@@ -70,6 +70,7 @@ func TestGetVirtualMachinesSuccess(t *testing.T) {
 			if err != nil {
 				t.Fatalf("unexpected error at client create: %s", err)
 			}
+			defer c.Stop()
 			ac := &apiConfig{
 				c:              c,
 				subscriptionID: "some-id",

lib/promscrape/discovery/consul/api.go

@@ -90,6 +90,7 @@ func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 	}
 	dc, err := getDatacenter(client, sdc.Datacenter)
 	if err != nil {
+		client.Stop()
 		return nil, fmt.Errorf("cannot obtain consul datacenter: %w", err)
 	}
 

lib/promscrape/discovery/digitalocean/digitalocean.go

@@ -155,5 +155,9 @@ func addDropletLabels(droplets []droplet, defaultPort int) []*promutils.Labels {
 
 // MustStop stops further usage for sdc.
 func (sdc *SDConfig) MustStop() {
-	configMap.Delete(sdc)
+	v := configMap.Delete(sdc)
+	if v != nil {
+		cfg := v.(*apiConfig)
+		cfg.client.Stop()
+	}
 }

lib/promscrape/discovery/docker/docker.go

@@ -47,5 +47,9 @@ func (sdc *SDConfig) GetLabels(baseDir string) ([]*promutils.Labels, error) {
 
 // MustStop stops further usage for sdc.
 func (sdc *SDConfig) MustStop() {
-	configMap.Delete(sdc)
+	v := configMap.Delete(sdc)
+	if v != nil {
+		cfg := v.(*apiConfig)
+		cfg.client.Stop()
+	}
 }

lib/promscrape/discovery/dockerswarm/dockerswarm.go

@@ -56,5 +56,9 @@ func (sdc *SDConfig) GetLabels(baseDir string) ([]*promutils.Labels, error) {
 
 // MustStop stops further usage for sdc.
 func (sdc *SDConfig) MustStop() {
-	configMap.Delete(sdc)
+	v := configMap.Delete(sdc)
+	if v != nil {
+		cfg := v.(*apiConfig)
+		cfg.client.Stop()
+	}
 }

lib/promscrape/discovery/eureka/eureka.go

@@ -101,7 +101,11 @@ func (sdc *SDConfig) GetLabels(baseDir string) ([]*promutils.Labels, error) {
 
 // MustStop stops further usage for sdc.
 func (sdc *SDConfig) MustStop() {
-	configMap.Delete(sdc)
+	v := configMap.Delete(sdc)
+	if v != nil {
+		cfg := v.(*apiConfig)
+		cfg.client.Stop()
+	}
 }
 
 func addInstanceLabels(apps *applications) []*promutils.Labels {

lib/promscrape/discovery/gce/api.go

@@ -42,6 +42,7 @@ func newAPIConfig(sdc *SDConfig) (*apiConfig, error) {
 	if len(project) == 0 {
 		proj, err := getCurrentProject()
 		if err != nil {
+			client.CloseIdleConnections()
 			return nil, fmt.Errorf("cannot determine the current project; make sure `vmagent` runs inside GCE; error: %w", err)
 		}
 		project = proj
@@ -52,6 +53,7 @@ func newAPIConfig(sdc *SDConfig) (*apiConfig, error) {
 		// Autodetect the current zone.
 		zone, err := getCurrentZone()
 		if err != nil {
+			client.CloseIdleConnections()
 			return nil, fmt.Errorf("cannot determine the current zone; make sure `vmagent` runs inside GCE; error: %w", err)
 		}
 		zones = append(zones, zone)
@@ -62,6 +64,7 @@ func newAPIConfig(sdc *SDConfig) (*apiConfig, error) {
 		// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3202
 		zs, err := getZonesForProject(client, project)
 		if err != nil {
+			client.CloseIdleConnections()
 			return nil, fmt.Errorf("cannot obtain zones for project %q: %w", project, err)
 		}
 		zones = zs

lib/promscrape/discovery/gce/gce.go

@@ -73,5 +73,9 @@ func (sdc *SDConfig) GetLabels(baseDir string) ([]*promutils.Labels, error) {
 
 // MustStop stops further usage for sdc.
 func (sdc *SDConfig) MustStop() {
-	configMap.Delete(sdc)
+	v := configMap.Delete(sdc)
+	if v != nil {
+		cfg := v.(*apiConfig)
+		cfg.client.CloseIdleConnections()
+	}
 }

lib/promscrape/discovery/http/http.go

@@ -56,5 +56,9 @@ func addHTTPTargetLabels(src []httpGroupTarget, sourceURL string) []*promutils.L
 
 // MustStop stops further usage for sdc.
 func (sdc *SDConfig) MustStop() {
-	configMap.Delete(sdc)
+	v := configMap.Delete(sdc)
+	if v != nil {
+		cfg := v.(*apiConfig)
+		cfg.client.Stop()
+	}
 }

lib/promscrape/discovery/openstack/api.go

@@ -87,6 +87,7 @@ func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 		}
 		ac, err := opts.NewConfig()
 		if err != nil {
+			cfg.client.CloseIdleConnections()
 			return nil, err
 		}
 		cfg.client.Transport = &http.Transport{
@@ -107,6 +108,7 @@ func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 		sdcAuth = readCredentialsFromEnv()
 	}
 	if strings.HasSuffix(sdcAuth.IdentityEndpoint, "v2.0") {
+		cfg.client.CloseIdleConnections()
 		return nil, errors.New("identity_endpoint v2.0 is not supported")
 	}
 	// trim .0 from v3.0 for prometheus cfg compatibility
@@ -114,11 +116,13 @@ func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 
 	parsedURL, err := url.Parse(sdcAuth.IdentityEndpoint)
 	if err != nil {
+		cfg.client.CloseIdleConnections()
 		return nil, fmt.Errorf("cannot parse identity_endpoint: %s as url, err: %w", sdcAuth.IdentityEndpoint, err)
 	}
 	cfg.endpoint = parsedURL
 	tokenReq, err := buildAuthRequestBody(&sdcAuth)
 	if err != nil {
+		cfg.client.CloseIdleConnections()
 		return nil, err
 	}
 	cfg.authTokenReq = tokenReq

lib/promscrape/discovery/openstack/openstack.go

@@ -57,5 +57,9 @@ func (sdc *SDConfig) GetLabels(baseDir string) ([]*promutils.Labels, error) {
 
 // MustStop stops further usage for sdc.
 func (sdc *SDConfig) MustStop() {
-	configMap.Delete(sdc)
+	v := configMap.Delete(sdc)
+	if v != nil {
+		cfg := v.(*apiConfig)
+		cfg.client.CloseIdleConnections()
+	}
 }

lib/promscrape/discoveryutils/client.go

@@ -74,6 +74,12 @@ type HTTPClient struct {
 	ReadTimeout time.Duration
 }
 
+func (hc *HTTPClient) stop() {
+	// Close idle connections to server in order to free up resources.
+	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4724
+	hc.client.CloseIdleConnections()
+}
+
 var defaultDialer = &net.Dialer{}
 
 // NewClient returns new Client for the given args.
@@ -254,6 +260,8 @@ func (c *Client) APIServer() string {
 // Stop cancels all in-flight requests
 func (c *Client) Stop() {
 	c.clientCancel()
+	c.client.stop()
+	c.blockingClient.stop()
 }
 
 func doRequestWithPossibleRetry(hc *HTTPClient, req *http.Request) (*http.Response, error) {