[#541] Use default value if config param is unset after SIGHUP

Signed-off-by: Marina Biryukova <m.biryukova@yadro.com>

cmd/s3-gw/app_settings_test.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"os"
+	"testing"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/resolver"
+	"github.com/stretchr/testify/require"
+)
+
+func TestConfigReload(t *testing.T) {
+	f, err := os.CreateTemp("", "conf")
+	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, os.Remove(f.Name()))
+	}()
+
+	confData := `
+pprof:
+  enabled: true
+
+frostfsid:
+  contract: name.nns
+
+resolve_order:
+  - nns
+`
+
+	_, err = f.WriteString(confData)
+	require.NoError(t, err)
+	require.NoError(t, f.Close())
+
+	cfg := newSettings()
+
+	require.NoError(t, cfg.flags.Parse([]string{"--config", f.Name(), "--max_clients_count", "10"}))
+	require.NoError(t, cfg.reload())
+
+	require.True(t, cfg.config().GetBool(cfgPProfEnabled))
+	require.Equal(t, "name.nns", cfg.config().GetString(cfgFrostfsIDContract))
+	require.Equal(t, []string{resolver.NNSResolver}, cfg.config().GetStringSlice(cfgResolveOrder))
+	require.Equal(t, 10, cfg.config().GetInt(cfgMaxClientsCount))
+
+	require.NoError(t, os.Truncate(f.Name(), 0))
+	require.NoError(t, cfg.reload())
+
+	require.False(t, cfg.config().GetBool(cfgPProfEnabled))
+	require.Equal(t, "frostfsid.frostfs", cfg.config().GetString(cfgFrostfsIDContract))
+	require.Equal(t, []string{resolver.DNSResolver}, cfg.config().GetStringSlice(cfgResolveOrder))
+	require.Equal(t, 10, cfg.config().GetInt(cfgMaxClientsCount))
+}