test(promtail): Fix flaky test with promtail bind port. (#6859)

* test(promtail): Fix flaky test with promtail bind port.

You cannot run promtail tests if there is already running promtail in your local.
e.g:
```
$ go test -run TestPromtail ./clients/pkg/promtail/
```

It gives you error
```
--- FAIL: TestPromtail (0.02s)
    promtail_test.go:112: error creating promtail listen tcp 127.0.0.1:9080: bind: address already in use
FAIL
FAIL	github.com/grafana/loki/clients/pkg/promtail	0.043s
```
Cause for the error is, test uses static default port (the same we use for promtail normally) in tests.

This is not **too** annonying if seen in isolation. But mainly annoying in two cases particularly
1. Hard to run tests parallely in general with these kind of static ports
2. These are causing some real problems in some integeration tests on GEL which starts docker-compose to run some test suites and
even stopping containers won't release ports soon enough making CI fail randomly.

This PR takes advantage of Go idiom of passing `port=0` to http (and also grpc) servers enforce Go's `net` package to bind some unused random ports. Making each test run choose random ports
enabling easy running theses tests in parallel.

NOTE: This PR also contains upgrade in `common/server` package that made this fix possible.
weaveworks/common#249

Signed-off-by: Kaviraj <kavirajkanagaraj@gmail.com>

* go mod tidy

Signed-off-by: Kaviraj <kavirajkanagaraj@gmail.com>

clients/pkg/promtail/promtail_test.go

@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"math"
 	"math/rand"
+	"net"
 	"net/http"
 	"net/url"
 	"os"
@@ -36,15 +37,14 @@ import (
 	"github.com/grafana/loki/clients/pkg/promtail/positions"
 	"github.com/grafana/loki/clients/pkg/promtail/scrapeconfig"
 	"github.com/grafana/loki/clients/pkg/promtail/server"
+	pserver "github.com/grafana/loki/clients/pkg/promtail/server"
 	file2 "github.com/grafana/loki/clients/pkg/promtail/targets/file"
 
 	"github.com/grafana/loki/pkg/logproto"
 	"github.com/grafana/loki/pkg/util"
 	util_log "github.com/grafana/loki/pkg/util/log"
 )
 
-const httpTestPort = 9080
-
 var clientMetrics = client.NewMetrics(prometheus.DefaultRegisterer, nil)
 
 func TestPromtail(t *testing.T) {
@@ -122,6 +122,10 @@ func TestPromtail(t *testing.T) {
 	}()
 	defer p.Shutdown() // In case the test fails before the call to Shutdown below.
 
+	svr := p.server.(*pserver.PromtailServer)
+
+	httpListenAddr := svr.Server.HTTPListenAddr()
+
 	expectedCounts := map[string]int{}
 
 	startupMarkerFile := testDir + "/startupMarker.log"
@@ -202,7 +206,7 @@ func TestPromtail(t *testing.T) {
 	<-time.After(500 * time.Millisecond)
 
 	// Pull out some prometheus metrics before shutting down
-	metricsBytes, contentType := getPromMetrics(t)
+	metricsBytes, contentType := getPromMetrics(t, httpListenAddr)
 
 	p.Shutdown()
 
@@ -496,8 +500,8 @@ func (h *testServerHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	h.recMtx.Unlock()
 }
 
-func getPromMetrics(t *testing.T) ([]byte, string) {
-	resp, err := http.Get(fmt.Sprintf("http://localhost:%d/metrics", httpTestPort))
+func getPromMetrics(t *testing.T, httpListenAddr net.Addr) ([]byte, string) {
+	resp, err := http.Get(fmt.Sprintf("http://%s/metrics", httpListenAddr))
 	if err != nil {
 		t.Fatal("Could not query metrics endpoint", err)
 	}
@@ -561,7 +565,11 @@ func buildTestConfig(t *testing.T, positionsFileName string, logDirName string)
 	cfg.ServerConfig.HTTPListenAddress = hostname
 	cfg.ServerConfig.ExternalURL = hostname
 	cfg.ServerConfig.GRPCListenAddress = hostname
-	cfg.ServerConfig.HTTPListenPort = httpTestPort
+
+	// NOTE: setting port to `0` makes it bind to some unused random port.
+	// enabling tests run more self contained and easy to run tests in parallel.
+	cfg.ServerConfig.HTTPListenPort = 0
+	cfg.ServerConfig.GRPCListenPort = 0
 
 	// Override some of those defaults
 	cfg.ClientConfig.URL = clientURL

clients/pkg/promtail/server/server.go

@@ -36,7 +36,7 @@ type Server interface {
 }
 
 // Server embed weaveworks server with static file and templating capability
-type server struct {
+type PromtailServer struct {
 	*serverww.Server
 	log               log.Logger
 	tms               *targets.TargetManagers
@@ -88,7 +88,7 @@ func New(cfg Config, log log.Logger, tms *targets.TargetManagers, promtailCfg st
 		healthCheckTargetFlag = *cfg.HealthCheckTarget
 	}
 
-	serv := &server{
+	serv := &PromtailServer{
 		Server:            wws,
 		log:               log,
 		tms:               tms,
@@ -108,7 +108,7 @@ func New(cfg Config, log log.Logger, tms *targets.TargetManagers, promtailCfg st
 }
 
 // serviceDiscovery serves the service discovery page.
-func (s *server) serviceDiscovery(rw http.ResponseWriter, req *http.Request) {
+func (s *PromtailServer) serviceDiscovery(rw http.ResponseWriter, req *http.Request) {
 	var index []string
 	allTarget := s.tms.AllTargets()
 	for job := range allTarget {
@@ -175,7 +175,7 @@ func (s *server) serviceDiscovery(rw http.ResponseWriter, req *http.Request) {
 	})
 }
 
-func (s *server) config(rw http.ResponseWriter, req *http.Request) {
+func (s *PromtailServer) config(rw http.ResponseWriter, req *http.Request) {
 	executeTemplate(req.Context(), rw, templateOptions{
 		Data:         s.promtailCfg,
 		BuildVersion: version.Info(),
@@ -186,7 +186,7 @@ func (s *server) config(rw http.ResponseWriter, req *http.Request) {
 }
 
 // targets serves the targets page.
-func (s *server) targets(rw http.ResponseWriter, req *http.Request) {
+func (s *PromtailServer) targets(rw http.ResponseWriter, req *http.Request) {
 	executeTemplate(req.Context(), rw, templateOptions{
 		Data: struct {
 			TargetPools map[string][]target.Target
@@ -219,7 +219,7 @@ func (s *server) targets(rw http.ResponseWriter, req *http.Request) {
 }
 
 // ready serves the ready endpoint
-func (s *server) ready(rw http.ResponseWriter, _ *http.Request) {
+func (s *PromtailServer) ready(rw http.ResponseWriter, _ *http.Request) {
 	if s.healthCheckTarget && !s.tms.Ready() {
 		http.Error(rw, readinessProbeFailure, http.StatusInternalServerError)
 		return

go.mod

@@ -92,7 +92,7 @@ require (
 	github.com/thanos-io/thanos v0.22.0
 	github.com/tonistiigi/fifo v0.0.0-20190226154929-a9fb20d87448
 	github.com/uber/jaeger-client-go v2.30.0+incompatible
-	github.com/weaveworks/common v0.0.0-20220706100410-67d27ed40fae
+	github.com/weaveworks/common v0.0.0-20220809154356-72ba250fe659
 	github.com/xdg-go/scram v1.0.2
 	go.etcd.io/bbolt v1.3.6
 	go.uber.org/atomic v1.9.0

go.sum

@@ -1581,8 +1581,8 @@ github.com/vultr/govultr/v2 v2.17.1 h1:UBmotwA0mkGtyJMakUF9jhLH/W3mN5wfGRn543i/B
 github.com/vultr/govultr/v2 v2.17.1/go.mod h1:ZFOKGWmgjytfyjeyAdhQlSWwTjh2ig+X49cAp50dzXI=
 github.com/wavefronthq/wavefront-sdk-go v0.9.2/go.mod h1:hQI6y8M9OtTCtc0xdwh+dCER4osxXdEAeCpacjpDZEU=
 github.com/weaveworks/common v0.0.0-20210913144402-035033b78a78/go.mod h1:YU9FvnS7kUnRt6HY10G+2qHkwzP3n3Vb1XsXDsJTSp8=
-github.com/weaveworks/common v0.0.0-20220706100410-67d27ed40fae h1:Z8YibUpdBEdCq8nwrYXJQ8vYooevbmEBIdFpseXK3/8=
-github.com/weaveworks/common v0.0.0-20220706100410-67d27ed40fae/go.mod h1:YfOOLoW1Q/jIIu0WLeSwgStmrKjuJEZSKTAUc+0KFvE=
+github.com/weaveworks/common v0.0.0-20220809154356-72ba250fe659 h1:McPAXT5tVW1NVs7SSGOCU2EzLyiUdygrGKZJZMTYZgA=
+github.com/weaveworks/common v0.0.0-20220809154356-72ba250fe659/go.mod h1:YfOOLoW1Q/jIIu0WLeSwgStmrKjuJEZSKTAUc+0KFvE=
 github.com/weaveworks/promrus v1.2.0 h1:jOLf6pe6/vss4qGHjXmGz4oDJQA+AOCqEL3FvvZGz7M=
 github.com/weaveworks/promrus v1.2.0/go.mod h1:SaE82+OJ91yqjrE1rsvBWVzNZKcHYFtMUyS1+Ogs/KA=
 github.com/willf/bitset v1.1.11 h1:N7Z7E9UvjW+sGsEl7k/SJrvY2reP1A07MrGuCjIOjRE=

vendor/modules.txt

@@ -1047,7 +1047,7 @@ github.com/uber/jaeger-lib/metrics/prometheus
 # github.com/ugorji/go/codec v1.1.7
 ## explicit
 github.com/ugorji/go/codec
-# github.com/weaveworks/common v0.0.0-20220706100410-67d27ed40fae
+# github.com/weaveworks/common v0.0.0-20220809154356-72ba250fe659
 ## explicit; go 1.14
 github.com/weaveworks/common/aws
 github.com/weaveworks/common/errors