updater: refactoring and set DNS server correctly

- Fix CLI operation not setting DNS server
- Fix periodic operation not setting DNS server
- Set DNS address for resolution once at start for both CLI and periodic operation
- Inject resolver to each provider instead of creating it within
- Use resolver settings on every call to `.Resolve` method, instead of passing it to constructor
- Move out minServers check from resolver

internal/provider/hidemyass/updater/resolve.go

@@ -6,7 +6,7 @@ import (
 	"github.com/qdm12/gluetun/internal/updater/resolver"
 )
 
-func newParallelResolver() *resolver.Parallel {
+func parallelResolverSettings(hosts []string) (settings resolver.ParallelSettings) {
 	const (
 		maxFailRatio    = 0.1
 		maxDuration     = 15 * time.Second
@@ -14,7 +14,8 @@ func newParallelResolver() *resolver.Parallel {
 		maxNoNew        = 2
 		maxFails        = 2
 	)
-	settings := resolver.ParallelSettings{
+	return resolver.ParallelSettings{
+		Hosts:        hosts,
 		MaxFailRatio: maxFailRatio,
 		Repeat: resolver.RepeatSettings{
 			MaxDuration:     maxDuration,
@@ -24,5 +25,4 @@ func newParallelResolver() *resolver.Parallel {
 			SortIPs:         true,
 		},
 	}
-	return resolver.NewParallelResolver(settings)
 }

internal/provider/hidemyass/updater/servers.go

@@ -26,7 +26,8 @@ func (u *Updater) FetchServers(ctx context.Context, minServers int) (
 			common.ErrNotEnoughServers, len(hosts), minServers)
 	}
 
-	hostToIPs, warnings, err := u.presolver.Resolve(ctx, hosts, minServers)
+	resolveSettings := parallelResolverSettings(hosts)
+	hostToIPs, warnings, err := u.presolver.Resolve(ctx, resolveSettings)
 	for _, warning := range warnings {
 		u.warner.Warn(warning)
 	}
@@ -34,6 +35,11 @@ func (u *Updater) FetchServers(ctx context.Context, minServers int) (
 		return nil, err
 	}
 
+	if len(hostToIPs) < minServers {
+		return nil, fmt.Errorf("%w: %d and expected at least %d",
+			common.ErrNotEnoughServers, len(servers), minServers)
+	}
+
 	servers = make([]models.Server, 0, len(hostToIPs))
 	for host, IPs := range hostToIPs {
 		tcpURL, tcp := tcpHostToURL[host]

internal/provider/hidemyass/updater/updater.go

@@ -12,10 +12,11 @@ type Updater struct {
 	warner    common.Warner
 }
 
-func New(client *http.Client, warner common.Warner) *Updater {
+func New(client *http.Client, warner common.Warner,
+	parallelResolver common.ParallelResolver) *Updater {
 	return &Updater{
 		client:    client,
-		presolver: newParallelResolver(),
+		presolver: parallelResolver,
 		warner:    warner,
 	}
 }