clients/pkg/promtail/targets/gcplog: avoid listening on 0.0.0.0 (#10411)

**What this PR does / why we need it**: Previously on Mac, running these
tests triggers a dialog box asking me to accept all incoming network
connections. Edit the test to listen on localhost only.

**Which issue(s) this PR fixes**:
Updates #10407

**Special notes for your reviewer**:

**Checklist**
- [x] Reviewed the
[`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md)
guide (**required**)
- [x] Documentation added (Just test changes, no documentation changes)
- [X] Tests updated
- [x] `CHANGELOG.md` updated (Not worth adding to CHANGELOG)
- [x] If the change is worth mentioning in the release notes, add
`add-to-release-notes` label (Not worth adding to release notes)
- [x] Changes that require user attention or interaction to upgrade are
documented in `docs/sources/setup/upgrade/_index.md` (No user attention
required)
- [x] For Helm chart changes bump the Helm chart version in
`production/helm/loki/Chart.yaml` and update
`production/helm/loki/CHANGELOG.md` and
`production/helm/loki/README.md`. [Example
PR](d10549e3ec)
(No need to do this)

clients/pkg/promtail/targets/gcplog/push_target_test.go

@@ -1,9 +1,7 @@
 package gcplog_test
 
 import (
-	"flag"
 	"fmt"
-	"net"
 	"net/http"
 	"os"
 	"strings"
@@ -14,7 +12,6 @@ import (
 	"github.com/grafana/loki/clients/pkg/promtail/api"
 
 	"github.com/go-kit/log"
-	"github.com/grafana/dskit/server"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/model/relabel"
@@ -162,7 +159,7 @@ func TestPushTarget(t *testing.T) {
 			eh := fake.New(func() {})
 			defer eh.Stop()
 
-			serverConfig, port, err := getServerConfigWithAvailablePort()
+			serverConfig, port, err := gcplog.GetServerConfigWithAvailablePort()
 			require.NoError(t, err, "error generating server config or finding open port")
 			config := &scrapeconfig.GcplogTargetConfig{
 				Server:               serverConfig,
@@ -224,7 +221,7 @@ func TestPushTarget_UseIncomingTimestamp(t *testing.T) {
 	eh := fake.New(func() {})
 	defer eh.Stop()
 
-	serverConfig, port, err := getServerConfigWithAvailablePort()
+	serverConfig, port, err := gcplog.GetServerConfigWithAvailablePort()
 	require.NoError(t, err, "error generating server config or finding open port")
 	config := &scrapeconfig.GcplogTargetConfig{
 		Server:               serverConfig,
@@ -268,7 +265,7 @@ func TestPushTarget_UseTenantIDHeaderIfPresent(t *testing.T) {
 	eh := fake.New(func() {})
 	defer eh.Stop()
 
-	serverConfig, port, err := getServerConfigWithAvailablePort()
+	serverConfig, port, err := gcplog.GetServerConfigWithAvailablePort()
 	require.NoError(t, err, "error generating server config or finding open port")
 	config := &scrapeconfig.GcplogTargetConfig{
 		Server:               serverConfig,
@@ -321,7 +318,7 @@ func TestPushTarget_ErroneousPayloadsAreRejected(t *testing.T) {
 	eh := fake.New(func() {})
 	defer eh.Stop()
 
-	serverConfig, port, err := getServerConfigWithAvailablePort()
+	serverConfig, port, err := gcplog.GetServerConfigWithAvailablePort()
 	require.NoError(t, err, "error generating server config or finding open port")
 	config := &scrapeconfig.GcplogTargetConfig{
 		Server:           serverConfig,
@@ -401,7 +398,7 @@ func TestPushTarget_UsePushTimeout(t *testing.T) {
 	eh := newBlockingEntryHandler()
 	defer eh.Stop()
 
-	serverConfig, port, err := getServerConfigWithAvailablePort()
+	serverConfig, port, err := gcplog.GetServerConfigWithAvailablePort()
 	require.NoError(t, err, "error generating server config or finding open port")
 	config := &scrapeconfig.GcplogTargetConfig{
 		Server:               serverConfig,
@@ -442,29 +439,3 @@ func waitForMessages(eh *fake.Client) {
 		countdown--
 	}
 }
-
-func getServerConfigWithAvailablePort() (cfg server.Config, port int, err error) {
-	// Get a randomly available port by open and closing a TCP socket
-	addr, err := net.ResolveTCPAddr("tcp", localhost+":0")
-	if err != nil {
-		return
-	}
-	l, err := net.ListenTCP("tcp", addr)
-	if err != nil {
-		return
-	}
-	port = l.Addr().(*net.TCPAddr).Port
-	err = l.Close()
-	if err != nil {
-		return
-	}
-
-	// Adjust some of the defaults
-	cfg.RegisterFlags(flag.NewFlagSet("empty", flag.ContinueOnError))
-	cfg.HTTPListenAddress = localhost
-	cfg.HTTPListenPort = port
-	cfg.GRPCListenAddress = localhost
-	cfg.GRPCListenPort = 0 // Not testing GRPC, a random port will be assigned
-
-	return
-}

clients/pkg/promtail/targets/gcplog/target_test.go

@@ -1,7 +1,9 @@
 package gcplog
 
 import (
+	"flag"
 	"fmt"
+	"net"
 	"os"
 	"reflect"
 	"testing"
@@ -13,6 +15,8 @@ import (
 	"golang.org/x/oauth2/google"
 	"google.golang.org/api/option"
 
+	"github.com/grafana/dskit/server"
+
 	"github.com/grafana/loki/clients/pkg/promtail/api"
 	"github.com/grafana/loki/clients/pkg/promtail/client/fake"
 	"github.com/grafana/loki/clients/pkg/promtail/scrapeconfig"
@@ -111,6 +115,11 @@ func TestNewGCPLogTarget(t *testing.T) {
 			// Since the push target underlying http server registers metrics in the default registerer, we have to override it to prevent duplicate metrics errors.
 			prometheus.DefaultRegisterer = prometheus.NewRegistry()
 
+			serverConfig, _, err := GetServerConfigWithAvailablePort()
+			if err != nil {
+				t.Fatal(err)
+			}
+			tt.args.config.Server = serverConfig
 			got, err := NewGCPLogTarget(tt.args.metrics, tt.args.logger, tt.args.handler, tt.args.relabel, tt.args.jobName, tt.args.config, option.WithCredentials(&google.Credentials{}))
 			// If the target was started, stop it after test
 			if got != nil {
@@ -126,3 +135,31 @@ func TestNewGCPLogTarget(t *testing.T) {
 		})
 	}
 }
+
+const localhost = "127.0.0.1"
+
+func GetServerConfigWithAvailablePort() (cfg server.Config, port int, err error) {
+	// Get a randomly available port by open and closing a TCP socket
+	addr, err := net.ResolveTCPAddr("tcp", localhost+":0")
+	if err != nil {
+		return
+	}
+	l, err := net.ListenTCP("tcp", addr)
+	if err != nil {
+		return
+	}
+	port = l.Addr().(*net.TCPAddr).Port
+	err = l.Close()
+	if err != nil {
+		return
+	}
+
+	// Adjust some of the defaults
+	cfg.RegisterFlags(flag.NewFlagSet("empty", flag.ContinueOnError))
+	cfg.HTTPListenAddress = localhost
+	cfg.HTTPListenPort = port
+	cfg.GRPCListenAddress = localhost
+	cfg.GRPCListenPort = 0 // Not testing GRPC, a random port will be assigned
+
+	return
+}