PMM-9224: Not disable fetching diagnostic info for arbiter (#655)

* PMM-9224: Enable diagnostic info for arbiter

* PMM-9224: Configure authentication to Arbiter when it requires authentication

* PMM-9224: Ignore linter error

* PMM-9224: Refactor code

* PMM-9224: Fix import order

Author: dliakhov

exporter/dsn_fix/dsn_fix.go

@@ -19,6 +19,7 @@ package dsn_fix
 import (
 	"net/url"
 
+	"github.com/AlekSi/pointer"
 	"go.mongodb.org/mongo-driver/mongo/options"
 )
 
@@ -41,6 +42,8 @@ func ClientOptionsForDSN(dsn string) (*options.ClientOptions, error) {
 	if username != "" || password != "" {
 		clientOptions.Auth.Username = username
 		clientOptions.Auth.Password = password
+		// set this flag to connect to arbiter when there authentication is enabled
+		clientOptions.AuthenticateToAnything = pointer.ToBool(true) //nolint:staticcheck
 	}
 
 	return clientOptions, nil

exporter/exporter.go

@@ -173,7 +173,6 @@ func (e *Exporter) makeRegistry(ctx context.Context, client *mongo.Client, topol
 
 	// arbiter only have isMaster privileges
 	if isArbiter {
-		e.opts.EnableDiagnosticData = false
 		e.opts.EnableDBStats = false
 		e.opts.EnableCollStats = false
 		e.opts.EnableTopMetrics = false