Add readonly tooling

pkg/commands/admin.go

@@ -222,3 +222,39 @@ func handleStolonDBUid(w http.ResponseWriter, r *http.Request) {
 
 	render.Err(w, errors.New("can't find db"))
 }
+
+func handleEnableReadonly(w http.ResponseWriter, r *http.Request) {
+	conn, close, err := localConnection(r.Context())
+	if err != nil {
+		render.Err(w, err)
+		return
+	}
+	defer close()
+
+	err = admin.SetReadonly(r.Context(), conn, true)
+	if err != nil {
+		render.Err(w, err)
+	}
+
+	resp := &Response{Result: true}
+
+	render.JSON(w, resp, http.StatusOK)
+}
+
+func handleDisableReadonly(w http.ResponseWriter, r *http.Request) {
+	conn, close, err := localConnection(r.Context())
+	if err != nil {
+		render.Err(w, err)
+		return
+	}
+	defer close()
+
+	err = admin.SetReadonly(r.Context(), conn, false)
+	if err != nil {
+		render.Err(w, err)
+	}
+
+	resp := &Response{Result: true}
+
+	render.JSON(w, resp, http.StatusOK)
+}

pkg/commands/handler.go

@@ -33,6 +33,8 @@ func Handler() http.Handler {
 		r.Get("/restart", handleRestart)
 		r.Get("/settings/view", handleViewSettings)
 		r.Get("/replicationstats", handleReplicationStats)
+		r.Post("/readonly/enable", handleEnableReadonly)
+		r.Post("/readonly/disable", handleDisableReadonly)
 		r.Get("/dbuid", handleStolonDBUid)
 		r.Post("/settings/update", handleUpdateSettings)
 	})

pkg/flypg/admin/admin.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"crypto/md5"
 	"fmt"
+	"github.com/pkg/errors"
 	"os"
 	"strings"
 
@@ -276,6 +277,35 @@ func ResolveReplicationLag(ctx context.Context, pg *pgx.Conn) ([]*ReplicationSta
 	return stats, nil
 }
 
+func SetReadonly(ctx context.Context, pg *pgx.Conn, enable bool) error {
+	role, err := ResolveRole(ctx, pg)
+	if err != nil {
+		return err
+	}
+	if role != "leader" {
+		return errors.New("can't set non primary to read-only")
+	}
+
+	databases, err := ListDatabases(ctx, pg)
+	if err != nil {
+		return err
+	}
+
+	for _, db := range databases {
+		// exclude administrative dbs
+		if db.Name == "postgres" {
+			continue
+		}
+
+		sql := fmt.Sprintf("ALTER DATABASE %s SET default_transaction_read_only=%v;", db.Name, enable)
+		if _, err = pg.Exec(ctx, sql); err != nil {
+			return fmt.Errorf("failed to alter readonly state on db %s: %s", db.Name, err)
+		}
+	}
+
+	return nil
+}
+
 func ResolveSettings(ctx context.Context, pg *pgx.Conn, list []string) (*flypg.Settings, error) {
 	node, err := flypg.NewNode()
 	if err != nil {