lib/promscrape: follow-up after bced9fb978

- Document the bugfix at docs/CHANGELOG.md
- Wait until all the worker goroutines are done in consulWatcher.mustStop()
- Do not log `context canceled` errors when discovering consul serviceNames
- Removed explicit handling of gzipped responses at lib/promscrape/discoveryutils.Client,
  since this handling is automatically performed by net/http.Transport.
  See DisableCompression option at https://pkg.go.dev/net/http#Transport .
- Remove explicit handling of the proxyURL, since it is automatically handled
  by net/http.Transport. See Proxy option at https://pkg.go.dev/net/http#Transport .
- Expliticly set MaxIdleConnsPerHost, since its default value equals to 2.
  Such a small value may result in excess tcp connection churn
  when more than 2 concurrent requests are processed by lib/promscrape/discoveryutils.Client.
- Do not set explicitly the `Host` request header, since it is automatically set by net/http.Client.
- Backport the bugfix to the recently added nomad_sd_configs - see https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3367

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3468

docs/CHANGELOG.md

@@ -31,6 +31,7 @@ The following tip changes can be tested by building VictoriaMetrics components f
 * BUGFIX: [MetricsQL](https://docs.victoriametrics.com/MetricsQL.html): properly parse durations with uppercase suffixes such as `10S`, `5MS`, `1W`, etc. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3589).
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): fix a panic during target discovery when `vmagent` runs with `-promscrape.dropOriginalLabels` command-line flag. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3580). The bug has been introduced in [v1.85.0](https://docs.victoriametrics.com/CHANGELOG.html#v1850).
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): [dockerswarm_sd_configs](https://docs.victoriametrics.com/sd_configs.html#dockerswarm_sd_configs): properly encode `filters` field. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3579).
+* BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): fix possible resource leak after hot reload of the updated [consul_sd_configs](https://docs.victoriametrics.com/sd_configs.html#consul_sd_configs). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3468).
 
 
 ## [v1.85.3](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.85.3)

lib/promscrape/discovery/consul/watch.go

@@ -34,6 +34,7 @@ type consulWatcher struct {
 	servicesLock sync.Mutex
 	services     map[string]*serviceWatcher
 
+	servicesWG sync.WaitGroup
 	wg         sync.WaitGroup
 	stopCh     chan struct{}
 }
@@ -73,7 +74,11 @@ func newConsulWatcher(client *discoveryutils.Client, sdc *SDConfig, datacenter,
 		stopCh:                make(chan struct{}),
 	}
 	initCh := make(chan struct{})
-	go cw.watchForServicesUpdates(initCh)
+	cw.wg.Add(1)
+	go func() {
+		cw.watchForServicesUpdates(initCh)
+		cw.wg.Done()
+	}()
 	// wait for initialization to complete
 	<-initCh
 	return cw
@@ -82,6 +87,7 @@ func newConsulWatcher(client *discoveryutils.Client, sdc *SDConfig, datacenter,
 func (cw *consulWatcher) mustStop() {
 	close(cw.stopCh)
 	cw.client.Stop()
+	cw.wg.Wait()
 }
 
 func (cw *consulWatcher) updateServices(serviceNames []string) {
@@ -98,14 +104,14 @@ func (cw *consulWatcher) updateServices(serviceNames []string) {
 			stopCh:      make(chan struct{}),
 		}
 		cw.services[serviceName] = sw
-		cw.wg.Add(1)
+		cw.servicesWG.Add(1)
 		serviceWatchersCreated.Inc()
 		initWG.Add(1)
 		go func() {
 			serviceWatchersCount.Inc()
 			sw.watchForServiceNodesUpdates(cw, &initWG)
 			serviceWatchersCount.Dec()
-			cw.wg.Done()
+			cw.servicesWG.Done()
 		}()
 	}
 
@@ -136,11 +142,13 @@ func (cw *consulWatcher) updateServices(serviceNames []string) {
 // watchForServicesUpdates closes the initCh once the initialization is complete and first discovery iteration is done.
 func (cw *consulWatcher) watchForServicesUpdates(initCh chan struct{}) {
 	index := int64(0)
-	clientAddr := cw.client.Addr()
+	apiServer := cw.client.APIServer()
 	f := func() {
 		serviceNames, newIndex, err := cw.getBlockingServiceNames(index)
 		if err != nil {
-			logger.Errorf("cannot obtain Consul serviceNames from %q: %s", clientAddr, err)
+			if !errors.Is(err, context.Canceled) {
+				logger.Errorf("cannot obtain Consul serviceNames from %q: %s", apiServer, err)
+			}
 			return
 		}
 		if index == newIndex {
@@ -151,7 +159,7 @@ func (cw *consulWatcher) watchForServicesUpdates(initCh chan struct{}) {
 		index = newIndex
 	}
 
-	logger.Infof("started Consul service watcher for %q", clientAddr)
+	logger.Infof("started Consul service watcher for %q", apiServer)
 	f()
 
 	// send signal that initialization is complete
@@ -165,15 +173,15 @@ func (cw *consulWatcher) watchForServicesUpdates(initCh chan struct{}) {
 		case <-ticker.C:
 			f()
 		case <-cw.stopCh:
-			logger.Infof("stopping Consul service watchers for %q", clientAddr)
+			logger.Infof("stopping Consul service watchers for %q", apiServer)
 			startTime := time.Now()
 			cw.servicesLock.Lock()
 			for _, sw := range cw.services {
 				close(sw.stopCh)
 			}
 			cw.servicesLock.Unlock()
-			cw.wg.Wait()
-			logger.Infof("stopped Consul service watcher for %q in %.3f seconds", clientAddr, time.Since(startTime).Seconds())
+			cw.servicesWG.Wait()
+			logger.Infof("stopped Consul service watcher for %q in %.3f seconds", apiServer, time.Since(startTime).Seconds())
 			return
 		}
 	}
@@ -219,16 +227,15 @@ func (cw *consulWatcher) getBlockingServiceNames(index int64) ([]string, int64,
 //
 // watchForServiceNodesUpdates calls initWG.Done() once the initialization is complete and the first discovery iteration is done.
 func (sw *serviceWatcher) watchForServiceNodesUpdates(cw *consulWatcher, initWG *sync.WaitGroup) {
-	clientAddr := cw.client.Addr()
+	apiServer := cw.client.APIServer()
 	index := int64(0)
 	path := "/v1/health/service/" + sw.serviceName + cw.serviceNodesQueryArgs
 	f := func() {
 		data, newIndex, err := getBlockingAPIResponse(cw.client, path, index)
 		if err != nil {
-			if errors.Is(err, context.Canceled) {
-				return
+			if !errors.Is(err, context.Canceled) {
+				logger.Errorf("cannot obtain Consul serviceNodes for serviceName=%q from %q: %s", sw.serviceName, apiServer, err)
 			}
-			logger.Errorf("cannot obtain Consul serviceNodes for serviceName=%q from %q: %s", sw.serviceName, clientAddr, err)
 			return
 		}
 		if index == newIndex {
@@ -237,7 +244,7 @@ func (sw *serviceWatcher) watchForServiceNodesUpdates(cw *consulWatcher, initWG
 		}
 		sns, err := parseServiceNodes(data)
 		if err != nil {
-			logger.Errorf("cannot parse Consul serviceNodes response for serviceName=%q from %q: %s", sw.serviceName, clientAddr, err)
+			logger.Errorf("cannot parse Consul serviceNodes response for serviceName=%q from %q: %s", sw.serviceName, apiServer, err)
 			return
 		}
 

lib/promscrape/discovery/nomad/api.go

@@ -3,6 +3,7 @@ package nomad
 import (
 	"flag"
 	"fmt"
+	"net/http"
 	"os"
 	"strconv"
 	"strings"
@@ -11,7 +12,6 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promauth"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promscrape/discoveryutils"
-	"github.com/VictoriaMetrics/fasthttp"
 )
 
 var waitTime = flag.Duration("promscrape.nomad.waitTime", 0, "Wait time used by Nomad service discovery. Default value is used if not set")
@@ -138,13 +138,13 @@ func maxWaitTime() time.Duration {
 func getBlockingAPIResponse(client *discoveryutils.Client, path string, index int64) ([]byte, int64, error) {
 	path += "&index=" + strconv.FormatInt(index, 10)
 	path += "&wait=" + fmt.Sprintf("%ds", int(maxWaitTime().Seconds()))
-	getMeta := func(resp *fasthttp.Response) {
-		ind := resp.Header.Peek("X-Nomad-Index")
+	getMeta := func(resp *http.Response) {
+		ind := resp.Header.Get("X-Nomad-Index")
 		if len(ind) == 0 {
 			logger.Errorf("cannot find X-Nomad-Index header in response from %q", path)
 			return
 		}
-		newIndex, err := strconv.ParseInt(string(ind), 10, 64)
+		newIndex, err := strconv.ParseInt(ind, 10, 64)
 		if err != nil {
 			logger.Errorf("cannot parse X-Nomad-Index header value in response from %q: %s", path, err)
 			return

lib/promscrape/discovery/nomad/watch.go

@@ -1,7 +1,9 @@
 package nomad
 
 import (
+	"context"
 	"encoding/json"
+	"errors"
 	"flag"
 	"fmt"
 	"net/url"
@@ -31,6 +33,7 @@ type nomadWatcher struct {
 	servicesLock sync.Mutex
 	services     map[string]*serviceWatcher
 
+	servicesWG sync.WaitGroup
 	wg         sync.WaitGroup
 	stopCh     chan struct{}
 }
@@ -61,7 +64,11 @@ func newNomadWatcher(client *discoveryutils.Client, sdc *SDConfig, datacenter, n
 		stopCh:                make(chan struct{}),
 	}
 	initCh := make(chan struct{})
-	go cw.watchForServicesUpdates(initCh)
+	cw.wg.Add(1)
+	go func() {
+		cw.watchForServicesUpdates(initCh)
+		cw.wg.Done()
+	}()
 	// wait for initialization to complete
 	<-initCh
 	return cw
@@ -69,9 +76,8 @@ func newNomadWatcher(client *discoveryutils.Client, sdc *SDConfig, datacenter, n
 
 func (cw *nomadWatcher) mustStop() {
 	close(cw.stopCh)
-	// Do not wait for the watcher to stop, since it may take
-	// up to discoveryutils.BlockingClientReadTimeout to complete.
-	// TODO: add ability to cancel blocking requests.
+	cw.client.Stop()
+	cw.wg.Wait()
 }
 
 func (cw *nomadWatcher) updateServices(serviceNames []string) {
@@ -88,14 +94,14 @@ func (cw *nomadWatcher) updateServices(serviceNames []string) {
 			stopCh:      make(chan struct{}),
 		}
 		cw.services[serviceName] = sw
-		cw.wg.Add(1)
+		cw.servicesWG.Add(1)
 		serviceWatchersCreated.Inc()
 		initWG.Add(1)
 		go func() {
 			serviceWatchersCount.Inc()
 			sw.watchForServiceAddressUpdates(cw, &initWG)
 			serviceWatchersCount.Dec()
-			cw.wg.Done()
+			cw.servicesWG.Done()
 		}()
 	}
 
@@ -126,11 +132,13 @@ func (cw *nomadWatcher) updateServices(serviceNames []string) {
 // watchForServicesUpdates closes the initCh once the initialization is complete and first discovery iteration is done.
 func (cw *nomadWatcher) watchForServicesUpdates(initCh chan struct{}) {
 	index := int64(0)
-	clientAddr := cw.client.Addr()
+	apiServer := cw.client.APIServer()
 	f := func() {
 		serviceNames, newIndex, err := cw.getBlockingServiceNames(index)
 		if err != nil {
-			logger.Errorf("cannot obtain Nomad serviceNames from %q: %s", clientAddr, err)
+			if !errors.Is(err, context.Canceled) {
+				logger.Errorf("cannot obtain Nomad serviceNames from %q: %s", apiServer, err)
+			}
 			return
 		}
 		if index == newIndex {
@@ -141,7 +149,7 @@ func (cw *nomadWatcher) watchForServicesUpdates(initCh chan struct{}) {
 		index = newIndex
 	}
 
-	logger.Infof("started Nomad service watcher for %q", clientAddr)
+	logger.Infof("started Nomad service watcher for %q", apiServer)
 	f()
 
 	// send signal that initialization is complete
@@ -155,15 +163,15 @@ func (cw *nomadWatcher) watchForServicesUpdates(initCh chan struct{}) {
 		case <-ticker.C:
 			f()
 		case <-cw.stopCh:
-			logger.Infof("stopping Nomad service watchers for %q", clientAddr)
+			logger.Infof("stopping Nomad service watchers for %q", apiServer)
 			startTime := time.Now()
 			cw.servicesLock.Lock()
 			for _, sw := range cw.services {
 				close(sw.stopCh)
 			}
 			cw.servicesLock.Unlock()
-			cw.wg.Wait()
-			logger.Infof("stopped Nomad service watcher for %q in %.3f seconds", clientAddr, time.Since(startTime).Seconds())
+			cw.servicesWG.Wait()
+			logger.Infof("stopped Nomad service watcher for %q in %.3f seconds", apiServer, time.Since(startTime).Seconds())
 			return
 		}
 	}
@@ -225,14 +233,16 @@ func (cw *nomadWatcher) getServiceSnapshot() map[string][]Service {
 //
 // watchForServiceNodesUpdates calls initWG.Done() once the initialization is complete and the first discovery iteration is done.
 func (sw *serviceWatcher) watchForServiceAddressUpdates(nw *nomadWatcher, initWG *sync.WaitGroup) {
-	clientAddr := nw.client.Addr()
+	apiServer := nw.client.APIServer()
 	index := int64(0)
 	// TODO: Maybe use a different query arg.
 	path := "/v1/service/" + sw.serviceName + nw.serviceNamesQueryArgs
 	f := func() {
 		data, newIndex, err := getBlockingAPIResponse(nw.client, path, index)
 		if err != nil {
-			logger.Errorf("cannot obtain Nomad services for serviceName=%q from %q: %s", sw.serviceName, clientAddr, err)
+			if !errors.Is(err, context.Canceled) {
+				logger.Errorf("cannot obtain Nomad services for serviceName=%q from %q: %s", sw.serviceName, apiServer, err)
+			}
 			return
 		}
 		if index == newIndex {
@@ -241,7 +251,7 @@ func (sw *serviceWatcher) watchForServiceAddressUpdates(nw *nomadWatcher, initWG
 		}
 		sns, err := parseServices(data)
 		if err != nil {
-			logger.Errorf("cannot parse Nomad services response for serviceName=%q from %q: %s", sw.serviceName, clientAddr, err)
+			logger.Errorf("cannot parse Nomad services response for serviceName=%q from %q: %s", sw.serviceName, apiServer, err)
 			return
 		}
 

lib/promscrape/discoveryutils/client.go

@@ -1,7 +1,6 @@
 package discoveryutils
 
 import (
-	"compress/gzip"
 	"context"
 	"crypto/tls"
 	"flag"
@@ -55,7 +54,7 @@ func GetHTTPClient() *http.Client {
 	return defaultClient
 }
 
-// Client is http client, which talks to the given apiServer.
+// Client is http client, which talks to the given apiServer passed to NewClient().
 type Client struct {
 	// client is used for short requests.
 	client *HTTPClient
@@ -65,8 +64,6 @@ type Client struct {
 
 	apiServer string
 
-	dialAddr string
-
 	setHTTPHeaders      func(req *http.Request)
 	setHTTPProxyHeaders func(req *http.Request)
 
@@ -81,110 +78,96 @@ type HTTPClient struct {
 	WriteTimeout time.Duration
 }
 
-func addMissingPort(addr string, isTLS bool) string {
-	if strings.Contains(addr, ":") {
-		return addr
-	}
-	if isTLS {
-		return addr + ":443"
-	}
-	return addr + ":80"
-}
+var defaultDialer = &net.Dialer{}
 
 // NewClient returns new Client for the given args.
 func NewClient(apiServer string, ac *promauth.Config, proxyURL *proxy.URL, proxyAC *promauth.Config) (*Client, error) {
 	u, err := url.Parse(apiServer)
 	if err != nil {
-		return nil, fmt.Errorf("cannot parse provided url %q: %w", apiServer, err)
+		return nil, fmt.Errorf("cannot parse apiServer=%q: %w", apiServer, err)
 	}
 
+	dialFunc := defaultDialer.DialContext
+	if u.Scheme == "unix" {
 		// special case for unix socket connection
-	var dialFunc func(addr string) (net.Conn, error)
-	if string(u.Scheme) == "unix" {
 		dialAddr := u.Path
-		apiServer = "http://"
-		dialFunc = func(_ string) (net.Conn, error) {
-			return net.Dial("unix", dialAddr)
+		apiServer = "http://unix"
+		dialFunc = func(ctx context.Context, _, _ string) (net.Conn, error) {
+			return defaultDialer.DialContext(ctx, "unix", dialAddr)
 		}
 	}
 
-	dialAddr := u.Host
-	isTLS := string(u.Scheme) == "https"
+	isTLS := u.Scheme == "https"
 	var tlsCfg *tls.Config
 	if isTLS {
 		tlsCfg = ac.NewTLSConfig()
 	}
 
-	setHTTPProxyHeaders := func(req *http.Request) {}
-
-	dialAddr = addMissingPort(dialAddr, isTLS)
-	if dialFunc == nil {
-		var err error
-		dialFunc, err = proxyURL.NewDialFunc(proxyAC)
-		if err != nil {
-			return nil, err
+	var proxyURLFunc func(*http.Request) (*url.URL, error)
+	if pu := proxyURL.GetURL(); pu != nil {
+		proxyURLFunc = http.ProxyURL(pu)
 	}
+
+	client := &http.Client{
+		Timeout: DefaultClientReadTimeout,
+		Transport: &http.Transport{
+			TLSClientConfig:       tlsCfg,
+			Proxy:                 proxyURLFunc,
+			TLSHandshakeTimeout:   10 * time.Second,
+			MaxIdleConnsPerHost:   *maxConcurrency,
+			ResponseHeaderTimeout: DefaultClientReadTimeout,
+			DialContext:           dialFunc,
+		},
+	}
+	blockingClient := &http.Client{
+		Timeout: BlockingClientReadTimeout,
+		Transport: &http.Transport{
+			TLSClientConfig:       tlsCfg,
+			Proxy:                 proxyURLFunc,
+			TLSHandshakeTimeout:   10 * time.Second,
+			MaxIdleConnsPerHost:   1000,
+			ResponseHeaderTimeout: BlockingClientReadTimeout,
+			DialContext:           dialFunc,
+		},
+	}
+
+	setHTTPHeaders := func(req *http.Request) {}
+	if ac != nil {
+		setHTTPHeaders = func(req *http.Request) {
+			ac.SetHeaders(req, true)
+		}
+	}
+	setHTTPProxyHeaders := func(req *http.Request) {}
 	if proxyAC != nil {
 		setHTTPProxyHeaders = func(req *http.Request) {
 			proxyURL.SetHeaders(proxyAC, req)
 		}
 	}
-	}
-
-	hcTransport := &http.Transport{
-		TLSClientConfig:       tlsCfg,
-		MaxConnsPerHost:       2 * *maxConcurrency,
-		ResponseHeaderTimeout: *maxWaitTime,
-		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
-			return dialFunc(dialAddr)
-		},
-	}
-
-	hc := &http.Client{
-		Timeout:   DefaultClientReadTimeout,
-		Transport: hcTransport,
-	}
-
-	blockingTransport := &http.Transport{
-		TLSClientConfig: tlsCfg,
-		MaxConnsPerHost: 64 * 1024,
-		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
-			return dialFunc(dialAddr)
-		},
-	}
-	blockingClient := &http.Client{
-		Timeout:   BlockingClientReadTimeout,
-		Transport: blockingTransport,
-	}
-
-	setHTTPHeaders := func(req *http.Request) {}
-	if ac != nil {
-		setHTTPHeaders = func(req *http.Request) { ac.SetHeaders(req, true) }
-	}
-
 	ctx, cancel := context.WithCancel(context.Background())
 
-	return &Client{
-		client:              &HTTPClient{client: hc, ReadTimeout: DefaultClientReadTimeout, WriteTimeout: DefaultClientWriteTimeout},
-		blockingClient:      &HTTPClient{client: blockingClient, ReadTimeout: BlockingClientReadTimeout, WriteTimeout: DefaultClientWriteTimeout},
+	c := &Client{
+		client: &HTTPClient{
+			client:       client,
+			ReadTimeout:  DefaultClientReadTimeout,
+			WriteTimeout: DefaultClientWriteTimeout,
+		},
+		blockingClient: &HTTPClient{
+			client:       blockingClient,
+			ReadTimeout:  BlockingClientReadTimeout,
+			WriteTimeout: DefaultClientWriteTimeout,
+		},
 		apiServer:           apiServer,
-		dialAddr:            dialAddr,
 		setHTTPHeaders:      setHTTPHeaders,
 		setHTTPProxyHeaders: setHTTPProxyHeaders,
 		clientCtx:           ctx,
 		clientCancel:        cancel,
-	}, nil
 	}
-
-// Addr returns the address the client connects to.
-func (c *Client) Addr() string {
-	return c.dialAddr
+	return c, nil
 }
 
 // GetAPIResponseWithReqParams returns response for given absolute path with optional callback for request.
-// modifyRequestParams should never reference data from request.
-func (c *Client) GetAPIResponseWithReqParams(path string, modifyRequestParams func(request *http.Request)) ([]byte, error) {
-	return c.getAPIResponse(path, modifyRequestParams)
+func (c *Client) GetAPIResponseWithReqParams(path string, modifyRequest func(request *http.Request)) ([]byte, error) {
+	return c.getAPIResponse(path, modifyRequest)
 }
 
 // GetAPIResponse returns response for the given absolute path.
@@ -205,12 +188,13 @@ func (c *Client) getAPIResponse(path string, modifyRequest func(request *http.Re
 		return nil, fmt.Errorf("too many outstanding requests to %q; try increasing -promscrape.discovery.concurrentWaitTime=%s or -promscrape.discovery.concurrency=%d",
 			c.apiServer, *maxWaitTime, *maxConcurrency)
 	}
-	defer func() { <-concurrencyLimitCh }()
+	defer func() {
+		<-concurrencyLimitCh
+	}()
 	return c.getAPIResponseWithParamsAndClient(c.client, path, modifyRequest, nil)
 }
 
 // GetBlockingAPIResponse returns response for given absolute path with blocking client and optional callback for api response,
-// inspectResponse - should never reference data from response.
 func (c *Client) GetBlockingAPIResponse(path string, inspectResponse func(resp *http.Response)) ([]byte, error) {
 	return c.getAPIResponseWithParamsAndClient(c.blockingClient, path, nil, inspectResponse)
 }
@@ -222,7 +206,6 @@ func (c *Client) getAPIResponseWithParamsAndClient(client *HTTPClient, path stri
 	if err != nil {
 		return nil, fmt.Errorf("cannot parse %q: %w", requestURL, err)
 	}
-	u.Host = c.dialAddr
 
 	deadline := time.Now().Add(client.WriteTimeout)
 	ctx, cancel := context.WithDeadline(c.clientCtx, deadline)
@@ -232,8 +215,6 @@ func (c *Client) getAPIResponseWithParamsAndClient(client *HTTPClient, path stri
 		return nil, fmt.Errorf("cannot create request for %q: %w", requestURL, err)
 	}
 
-	req.Header.Set("Host", c.dialAddr)
-	req.Header.Set("Accept-Encoding", "gzip")
 	c.setHTTPHeaders(req)
 	c.setHTTPProxyHeaders(req)
 	if modifyRequest != nil {
@@ -244,20 +225,11 @@ func (c *Client) getAPIResponseWithParamsAndClient(client *HTTPClient, path stri
 	if err != nil {
 		return nil, fmt.Errorf("cannot fetch %q: %w", requestURL, err)
 	}
-
-	reader := resp.Body
-	if resp.Header.Get("Content-Encoding") == "gzip" {
-		reader, err = gzip.NewReader(resp.Body)
-		if err != nil {
-			return nil, fmt.Errorf("cannot create gzip reader for %q: %w", requestURL, err)
-		}
-	}
-
-	data, err := io.ReadAll(reader)
-	if err != nil {
-		return nil, fmt.Errorf("cannot ungzip response from %q: %w", requestURL, err)
-	}
+	data, err := io.ReadAll(resp.Body)
 	_ = resp.Body.Close()
+	if err != nil {
+		return nil, fmt.Errorf("cannot read response from %q: %w", requestURL, err)
+	}
 
 	if inspectResponse != nil {
 		inspectResponse(resp)
@@ -280,10 +252,9 @@ func (c *Client) Stop() {
 	c.clientCancel()
 }
 
-// DoRequestWithPossibleRetry performs the given req at client and stores the response at resp.
-func DoRequestWithPossibleRetry(hc *HTTPClient, req *http.Request, requestCounter, retryCounter *metrics.Counter) (*http.Response, error) {
+func doRequestWithPossibleRetry(hc *HTTPClient, req *http.Request) (*http.Response, error) {
 	sleepTime := time.Second
-	requestCounter.Inc()
+	discoveryRequests.Inc()
 	deadline, ok := req.Context().Deadline()
 	if !ok {
 		deadline = time.Now().Add(hc.WriteTimeout)
@@ -309,14 +280,10 @@ func DoRequestWithPossibleRetry(hc *HTTPClient, req *http.Request, requestCounte
 			sleepTime = maxSleepTime
 		}
 		time.Sleep(sleepTime)
-		retryCounter.Inc()
+		discoveryRetries.Inc()
 	}
 }
 
-func doRequestWithPossibleRetry(hc *HTTPClient, req *http.Request) (*http.Response, error) {
-	return DoRequestWithPossibleRetry(hc, req, discoveryRequests, discoveryRetries)
-}
-
 var (
 	discoveryRequests = metrics.NewCounter(`vm_promscrape_discovery_requests_total`)
 	discoveryRetries  = metrics.NewCounter(`vm_promscrape_discovery_retries_total`)