roachprod: configure providers needed for DNS

Before this change, DNS would only sync if the AWS provider was active.
This is now configurable.

Epic: None

Release note: None

pkg/cmd/roachprod/flags.go

@@ -375,4 +375,10 @@ func initFlags() {
 			"sql-instance", 0, "specific SQL/HTTP instance to connect to (this is a roachprod abstraction distinct from the internal instance ID)")
 	}
 
+	for _, cmd := range []*cobra.Command{startCmd, listCmd, syncCmd} {
+		cmd.Flags().StringSliceVar(&config.DNSRequiredProviders,
+			"dns-required-providers", config.DefaultDNSRequiredProviders,
+			"the cloud providers that must be active to refresh DNS entries",
+		)
+	}
 }

pkg/roachprod/config/config.go

@@ -18,6 +18,7 @@ import (
 	"path"
 	"regexp"
 	"slices"
+	"strings"
 
 	"github.com/cockroachdb/cockroach/pkg/roachprod/logger"
 	"github.com/cockroachdb/cockroach/pkg/util/envutil"
@@ -57,6 +58,15 @@ var (
 
 	// EmailDomain used to form fully qualified usernames for gcloud and slack.
 	EmailDomain string
+
+	// DNSRequiredProviders is the list of cloud providers that must be active for
+	// DNS records to be synced when roachprod syncs its state.
+	DefaultDNSRequiredProviders = envOrDefaultStrings(
+		"ROACHPROD_DNS_REQUIRED_PROVIDERS", []string{"gce", "aws"},
+	)
+
+	// DNSRequiredProviders is the list of cloud providers that must be active for
+	DNSRequiredProviders []string
 )
 
 // EnvOrDefaultString returns the value of the environment variable with the
@@ -70,6 +80,13 @@ func EnvOrDefaultString(key, def string) string {
 	return def
 }
 
+func envOrDefaultStrings(key string, def []string) []string {
+	if v, ok := os.LookupEnv(key); ok {
+		return strings.Split(v, ",")
+	}
+	return def
+}
+
 func init() {
 	var err error
 	OSUser, err = user.Current()

pkg/roachprod/roachprod.go

@@ -274,8 +274,18 @@ func Sync(l *logger.Logger, options vm.ListOptions) (*cloud.Cloud, error) {
 			refreshDNS = false
 		}
 	}
-	if !vm.Providers[aws.ProviderName].Active() {
+	// If there are no DNS required providers, we shouldn't refresh DNS,
+	// it's probably a misconfiguration.
+	if len(config.DNSRequiredProviders) == 0 {
 		refreshDNS = false
+	} else {
+		// If any of the required providers is not active, we shouldn't refresh DNS.
+		for _, p := range config.DNSRequiredProviders {
+			if !vm.Providers[p].Active() {
+				refreshDNS = false
+				break
+			}
+		}
 	}
 	// DNS entries are maintained in the GCE DNS registry for all vms, from all
 	// clouds.