Watch a file to configure which domains should use new gitlab source

Instead of passing domain once in an ENV variable we now watcn a file
(specified with `GITLAB_NEW_SOURCE_DOMAINS_FILE`, defaults to
`.new-source-domains`) and read it when it's modified in order to find
which domains should use the new `gitlab` config source.

This way we can control this without having to restart Pages.

Related to https://gitlab.com/gitlab-org/gitlab-pages/issues/266.

3 files changed, 77 insertions, 9 deletions

diff --git a/acceptance_test.go b/acceptance_test.go
index ae1bf2b6..dac3776a 100644
--- a/acceptance_test.go
+++ b/acceptance_test.go
@@ -57,6 +57,11 @@ func skipUnlessEnabled(t *testing.T, conditions ...string) {
 				t.Log("Not supported with -daemon-inplace-chroot")
 				t.SkipNow()
 			}
+		case "not-daemonized":
+			if os.Getenv("TEST_DAEMONIZE") != "" {
+				t.Log("Not supported when daemonized")
+				t.SkipNow()
+			}
 		default:
 			t.Error("Unknown condition:", condition)
 			t.FailNow()
@@ -1529,15 +1534,16 @@ func TestTLSVersions(t *testing.T) {
 }
 
 func TestGitlabDomainsSource(t *testing.T) {
-	skipUnlessEnabled(t)
+	skipUnlessEnabled(t, "not-daemonized")
 
 	source := NewGitlabDomainsSourceStub(t)
 	defer source.Close()
 
-	newSourceDomains := "GITLAB_NEW_SOURCE_DOMAINS=new-source-test.gitlab.io,non-existent-domain.gitlab.io"
+	newSourceDomainsFile := CreateNewSourceDomainsFixtureFile(t, "new-source-test.gitlab.io\nnon-existent-domain.gitlab.io")
+	newSourceDomainsFile = "GITLAB_NEW_SOURCE_DOMAINS_FILE=" + newSourceDomainsFile
 	gitLabAPISecretKey := CreateGitLabAPISecretKeyFixtureFile(t)
 	pagesArgs := []string{"-gitlab-server", source.URL, "-api-secret-key", gitLabAPISecretKey}
-	teardown := RunPagesProcessWithEnvs(t, true, *pagesBinary, listeners, "", []string{newSourceDomains}, pagesArgs...)
+	teardown := RunPagesProcessWithEnvs(t, true, *pagesBinary, listeners, "", []string{newSourceDomainsFile}, pagesArgs...)
 	defer teardown()
 
 	t.Run("when a domain exists", func(t *testing.T) {
diff --git a/helpers_test.go b/helpers_test.go
index bcc43d63..8bb3b65d 100644
--- a/helpers_test.go
+++ b/helpers_test.go
@@ -85,6 +85,16 @@ func CreateGitLabAPISecretKeyFixtureFile(t *testing.T) (filepath string) {
 	return secretfile.Name()
 }
 
+func CreateNewSourceDomainsFixtureFile(t *testing.T, domains string) (filepath string) {
+	domainsfile, err := ioutil.TempFile("", "new-source-domains")
+	require.NoError(t, err)
+	domainsfile.Close()
+
+	require.NoError(t, ioutil.WriteFile(domainsfile.Name(), []byte(domains), 0644))
+
+	return domainsfile.Name()
+}
+
 // ListenSpec is used to point at a gitlab-pages http server, preserving the
 // type of port it is (http, https, proxy)
 type ListenSpec struct {
diff --git a/internal/source/domains.go b/internal/source/domains.go
index 85d06152..870a95fd 100644
--- a/internal/source/domains.go
+++ b/internal/source/domains.go
@@ -1,9 +1,12 @@
 package source
 
 import (
+	"bufio"
 	"errors"
 	"os"
-	"strings"
+	"time"
+
+	log "github.com/sirupsen/logrus"
 
 	"gitlab.com/gitlab-org/gitlab-pages/internal/domain"
 	"gitlab.com/gitlab-org/gitlab-pages/internal/source/disk"
@@ -14,15 +17,64 @@ var newSourceDomains []string
 var brokenSourceDomain string
 
 func init() {
-	testDomains := os.Getenv("GITLAB_NEW_SOURCE_DOMAINS")
-	if testDomains != "" {
-		newSourceDomains = strings.Split(testDomains, ",")
-	}
-
 	brokenDomain := os.Getenv("GITLAB_NEW_SOURCE_BROKEN_DOMAIN")
 	if brokenDomain != "" {
 		brokenSourceDomain = brokenDomain
 	}
+
+	go watchForNewSourceDomains(&newSourceDomains, 5*time.Second)
+}
+
+// watchForNewSourceDomains polls the filesystem and updates test domains if needed.
+func watchForNewSourceDomains(newSourceDomains *[]string, interval time.Duration) {
+	var lastUpdate time.Time
+
+	testDomainsFile := os.Getenv("GITLAB_NEW_SOURCE_DOMAINS_FILE")
+	if testDomainsFile == "" {
+		testDomainsFile = ".new-source-domains"
+	}
+
+	for {
+		fileinfo, err := os.Stat(testDomainsFile)
+		if err != nil {
+			if !os.IsNotExist(err) {
+				log.WithError(err).Warn("Failed to get stats for new source domains file")
+			}
+
+			time.Sleep(interval)
+			continue
+		}
+
+		if lastUpdate == fileinfo.ModTime() {
+			time.Sleep(interval)
+			continue
+		}
+
+		lastUpdate = fileinfo.ModTime()
+
+		file, err := os.Open(testDomainsFile)
+		if err != nil {
+			log.WithError(err).Warn("Failed to read new source domains file")
+		}
+
+		defer file.Close()
+
+		reader := bufio.NewReader(file)
+		scanner := bufio.NewScanner(reader)
+		scanner.Split(bufio.ScanLines)
+
+		domains := make([]string, 0)
+		for scanner.Scan() {
+			if len(scanner.Text()) > 0 {
+				domains = append(domains, scanner.Text())
+			}
+		}
+
+		*newSourceDomains = domains
+		log.Info("New source domains updated")
+
+		time.Sleep(interval)
+	}
 }
 
 // Domains struct represents a map of all domains supported by pages. It is