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/privado/updater/resolve.go

@@ -6,14 +6,15 @@ import (
 	"github.com/qdm12/gluetun/internal/updater/resolver"
 )
 
-func newParallelResolver() (parallelResolver *resolver.Parallel) {
+func parallelResolverSettings(hosts []string) (settings resolver.ParallelSettings) {
 	const (
 		maxFailRatio = 0.1
 		maxDuration  = 30 * time.Second
 		maxNoNew     = 2
 		maxFails     = 2
 	)
-	settings := resolver.ParallelSettings{
+	return resolver.ParallelSettings{
+		Hosts:        hosts,
 		MaxFailRatio: maxFailRatio,
 		Repeat: resolver.RepeatSettings{
 			MaxDuration: maxDuration,
@@ -22,5 +23,4 @@ func newParallelResolver() (parallelResolver *resolver.Parallel) {
 			SortIPs:     true,
 		},
 	}
-	return resolver.NewParallelResolver(settings)
 }

internal/provider/privado/updater/servers.go

@@ -50,7 +50,8 @@ func (u *Updater) FetchServers(ctx context.Context, minServers int) (
 	}
 
 	hosts := hts.toHostsSlice()
-	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)
 	}
@@ -58,6 +59,11 @@ 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)
+	}
+
 	hts.adaptWithIPs(hostToIPs)
 
 	servers = hts.toServersSlice()

internal/provider/privado/updater/updater.go

@@ -14,11 +14,11 @@ type Updater struct {
 }
 
 func New(client *http.Client, unzipper common.Unzipper,
-	warner common.Warner) *Updater {
+	warner common.Warner, parallelResolver common.ParallelResolver) *Updater {
 	return &Updater{
 		client:    client,
 		unzipper:  unzipper,
-		presolver: newParallelResolver(),
+		presolver: parallelResolver,
 		warner:    warner,
 	}
 }