[MM-30436] Add support for configuration custom defaults (#16265)

* [MM-30436] Add support for configuration custom defaults * Addressing review comments * Addressing PR comments * Soft fail if the configuration defaults cannot be read * Directly print error in log message * Fix linter Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
2020-11-16 15:25:48 +01:00
--- a/api4/apitestlib.go
+++ b/api4/apitestlib.go
@@ -92,7 +92,7 @@ func setupTestHelper(dbStore store.Store, searchEngine *searchengine.Broker, ent
 	}
 	memoryStore.Set(memoryConfig)

-	configStore, err := config.NewStoreFromBacking(memoryStore)
+	configStore, err := config.NewStoreFromBacking(memoryStore, nil)
 	if err != nil {
 		panic(err)
 	}
--- a/api4/config_test.go
+++ b/api4/config_test.go
@@ -686,11 +686,11 @@ func TestMigrateConfig(t *testing.T) {
 	})

 	th.TestForSystemAdminAndLocal(t, func(t *testing.T, client *model.Client4) {
-		f, err := config.NewStore("from.json", false)
+		f, err := config.NewStore("from.json", false, nil)
 		require.NoError(t, err)
 		defer f.RemoveFile("from.json")

-		_, err = config.NewStore("to.json", false)
+		_, err = config.NewStore("to.json", false, nil)
 		require.NoError(t, err)
 		defer f.RemoveFile("to.json")

--- a/app/options.go
+++ b/app/options.go
@@ -8,6 +8,7 @@ import (
 	"github.com/pkg/errors"

 	"github.com/mattermost/mattermost-server/v5/config"
+	"github.com/mattermost/mattermost-server/v5/model"
 	"github.com/mattermost/mattermost-server/v5/store"
 )

@@ -38,10 +39,13 @@ func StoreOverride(override interface{}) Option {
 	}
 }

-// Config applies the given config dsn, whether a path to config.json or a database connection string.
-func Config(dsn string, watch bool) Option {
+// Config applies the given config dsn, whether a path to config.json
+// or a database connection string. It receives as well a set of
+// custom defaults that will be applied for any unset property of the
+// config loaded from the dsn on top of the normal defaults
+func Config(dsn string, watch bool, configDefaults *model.Config) Option {
 	return func(s *Server) error {
-		configStore, err := config.NewStore(dsn, watch)
+		configStore, err := config.NewStore(dsn, watch, configDefaults)
 		if err != nil {
 			return errors.Wrap(err, "failed to apply Config option")
 		}
--- a/app/server.go
+++ b/app/server.go
@@ -210,7 +210,7 @@ func NewServer(options ...Option) (*Server, error) {
 		if err != nil {
 			return nil, errors.Wrap(err, "failed to load config")
 		}
-		configStore, err := config.NewStoreFromBacking(innerStore)
+		configStore, err := config.NewStoreFromBacking(innerStore, nil)
 		if err != nil {
 			return nil, errors.Wrap(err, "failed to load config")
 		}
--- a/app/server_test.go
+++ b/app/server_test.go
@@ -386,7 +386,7 @@ func TestSentry(t *testing.T) {

 		s, err := NewServer(func(server *Server) error {
 			configStore, _ := config.NewFileStore("config.json", true)
-			store, _ := config.NewStoreFromBacking(configStore)
+			store, _ := config.NewStoreFromBacking(configStore, nil)
 			server.configStore = store
 			server.UpdateConfig(func(cfg *model.Config) {
 				*cfg.ServiceSettings.ListenAddress = ":0"
@@ -437,7 +437,7 @@ func TestSentry(t *testing.T) {

 		s, err := NewServer(func(server *Server) error {
 			configStore, _ := config.NewFileStore("config.json", true)
-			store, _ := config.NewStoreFromBacking(configStore)
+			store, _ := config.NewStoreFromBacking(configStore, nil)
 			server.configStore = store
 			server.UpdateConfig(func(cfg *model.Config) {
 				*cfg.ServiceSettings.ListenAddress = ":0"
--- a/cmd/mattermost/commands/config.go
+++ b/cmd/mattermost/commands/config.go
@@ -145,7 +145,7 @@ func getConfigStore(command *cobra.Command) (*config.Store, error) {
 		return nil, errors.Wrap(err, "failed to initialize i18n")
 	}

-	configStore, err := config.NewStore(getConfigDSN(command, config.GetEnvironment()), false)
+	configStore, err := config.NewStore(getConfigDSN(command, config.GetEnvironment()), false, nil)
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to initialize config store")
 	}
--- a/cmd/mattermost/commands/config_test.go
+++ b/cmd/mattermost/commands/config_test.go
@@ -543,9 +543,9 @@ func TestConfigMigrate(t *testing.T) {
 	sqlDSN := getDsn(*sqlSettings.DriverName, *sqlSettings.DataSource)
 	fileDSN := "config.json"

-	ds, err := config.NewStore(sqlDSN, false)
+	ds, err := config.NewStore(sqlDSN, false, nil)
 	require.NoError(t, err)
-	fs, err := config.NewStore(fileDSN, false)
+	fs, err := config.NewStore(fileDSN, false, nil)
 	require.NoError(t, err)

 	defer ds.Close()
--- a/cmd/mattermost/commands/init.go
+++ b/cmd/mattermost/commands/init.go
@@ -32,7 +32,7 @@ func InitDBCommandContext(configDSN string) (*app.App, error) {
 	model.AppErrorInit(utils.T)

 	s, err := app.NewServer(
-		app.Config(configDSN, false),
+		app.Config(configDSN, false, nil),
 		app.StartSearchEngine,
 	)
 	if err != nil {
--- a/cmd/mattermost/commands/plugin_test.go
+++ b/cmd/mattermost/commands/plugin_test.go
@@ -37,7 +37,7 @@ func TestPlugin(t *testing.T) {

 	fs, err := config.NewFileStore(th.ConfigPath(), false)
 	require.Nil(t, err)
-	cfsStore, err := config.NewStoreFromBacking(fs)
+	cfsStore, err := config.NewStoreFromBacking(fs, nil)
 	require.Nil(t, err)
 	require.NotNil(t, cfsStore.Get().PluginSettings.PluginStates["testplugin"])
 	assert.True(t, cfsStore.Get().PluginSettings.PluginStates["testplugin"].Enable)
@@ -47,7 +47,7 @@ func TestPlugin(t *testing.T) {
 	assert.Contains(t, output, "Disabled plugin: testplugin")
 	fs, err = config.NewFileStore(th.ConfigPath(), false)
 	require.Nil(t, err)
-	cfsStore, err = config.NewStoreFromBacking(fs)
+	cfsStore, err = config.NewStoreFromBacking(fs, nil)
 	require.Nil(t, err)
 	require.NotNil(t, cfsStore.Get().PluginSettings.PluginStates["testplugin"])
 	assert.False(t, cfsStore.Get().PluginSettings.PluginStates["testplugin"].Enable)
--- a/cmd/mattermost/commands/server.go
+++ b/cmd/mattermost/commands/server.go
@@ -4,6 +4,7 @@
 package commands

 import (
+	"encoding/json"
 	"net"
 	"os"
 	"os/signal"
@@ -15,6 +16,7 @@ import (
 	"github.com/mattermost/mattermost-server/v5/config"
 	"github.com/mattermost/mattermost-server/v5/manualtesting"
 	"github.com/mattermost/mattermost-server/v5/mlog"
+	"github.com/mattermost/mattermost-server/v5/model"
 	"github.com/mattermost/mattermost-server/v5/utils"
 	"github.com/mattermost/mattermost-server/v5/web"
 	"github.com/mattermost/mattermost-server/v5/wsapi"
@@ -22,6 +24,8 @@ import (
 	"github.com/spf13/cobra"
 )

+const CUSTOM_DEFAULTS_ENV_VAR = "MM_CUSTOM_DEFAULTS_PATH"
+
 var serverCmd = &cobra.Command{
 	Use:          "server",
 	Short:        "Run the Mattermost server",
@@ -34,6 +38,27 @@ func init() {
 	RootCmd.RunE = serverCmdF
 }

+func loadCustomDefaults() (*model.Config, error) {
+	customDefaultsPath := os.Getenv(CUSTOM_DEFAULTS_ENV_VAR)
+	if customDefaultsPath == "" {
+		return nil, nil
+	}
+
+	file, err := os.Open(customDefaultsPath)
+	if err != nil {
+		return nil, errors.Wrapf(err, "unable to open custom defaults file at %q", customDefaultsPath)
+	}
+	defer file.Close()
+
+	var customDefaults *model.Config
+	err = json.NewDecoder(file).Decode(&customDefaults)
+	if err != nil {
+		return nil, errors.Wrap(err, "unable to decode custom defaults configuration")
+	}
+
+	return customDefaults, nil
+}
+
 func serverCmdF(command *cobra.Command, args []string) error {
 	disableConfigWatch, _ := command.Flags().GetBool("disableconfigwatch")
 	usedPlatform, _ := command.Flags().GetBool("platform")
@@ -41,9 +66,15 @@ func serverCmdF(command *cobra.Command, args []string) error {
 	interruptChan := make(chan os.Signal, 1)

 	if err := utils.TranslationsPreInit(); err != nil {
-		return errors.Wrapf(err, "unable to load Mattermost translation files")
+		return errors.Wrap(err, "unable to load Mattermost translation files")
 	}
-	configStore, err := config.NewStore(getConfigDSN(command, config.GetEnvironment()), !disableConfigWatch)
+
+	customDefaults, err := loadCustomDefaults()
+	if err != nil {
+		mlog.Error("Error loading custom configuration defaults: " + err.Error())
+	}
+
+	configStore, err := config.NewStore(getConfigDSN(command, config.GetEnvironment()), !disableConfigWatch, customDefaults)
 	if err != nil {
 		return errors.Wrap(err, "failed to load configuration")
 	}
--- a/config/common_test.go
+++ b/config/common_test.go
@@ -14,7 +14,7 @@ import (
 	"github.com/mattermost/mattermost-server/v5/model"
 )

-var emptyConfig, readOnlyConfig, minimalConfig, invalidConfig, fixesRequiredConfig, ldapConfig, testConfig *model.Config
+var emptyConfig, readOnlyConfig, minimalConfig, invalidConfig, fixesRequiredConfig, ldapConfig, testConfig, customConfigDefaults *model.Config

 func init() {
 	emptyConfig = &model.Config{}
@@ -72,6 +72,14 @@ func init() {
 			SiteURL: sToP("http://TestStoreNew"),
 		},
 	}
+	customConfigDefaults = &model.Config{
+		ServiceSettings: model.ServiceSettings{
+			SiteURL: model.NewString("http://custom.com"),
+		},
+		DisplaySettings: model.DisplaySettings{
+			ExperimentalTimezone: model.NewBool(false),
+		},
+	}
 }

 func TestMergeConfigs(t *testing.T) {
@@ -132,7 +140,7 @@ func TestMergeConfigs(t *testing.T) {
 func TestConfigEnvironmentOverrides(t *testing.T) {
 	memstore, err := config.NewMemoryStore()
 	require.NoError(t, err)
-	base, err := config.NewStoreFromBacking(memstore)
+	base, err := config.NewStoreFromBacking(memstore, nil)
 	require.NoError(t, err)
 	originalConfig := &model.Config{}
 	originalConfig.ServiceSettings.SiteURL = newString("http://notoverriden.ca")
@@ -161,7 +169,7 @@ func TestRemoveEnvironmentOverrides(t *testing.T) {

 	memstore, err := config.NewMemoryStore()
 	require.NoError(t, err)
-	base, err := config.NewStoreFromBacking(memstore)
+	base, err := config.NewStoreFromBacking(memstore, nil)
 	require.NoError(t, err)
 	oldCfg := base.Get()
 	assert.Equal(t, "http://overridden.ca", *oldCfg.ServiceSettings.SiteURL)
--- a/config/database_test.go
+++ b/config/database_test.go
@@ -115,12 +115,12 @@ func assertDatabaseNotEqualsConfig(t *testing.T, expectedCfg *model.Config) {
 	assert.NotEqual(t, expectedCfg, actualCfg)
 }

-func newTestDatabaseStore(t *testing.T) (*config.Store, error) {
+func newTestDatabaseStore(t *testing.T, customDefaults *model.Config) (*config.Store, error) {
 	sqlSettings := mainHelper.GetSQLSettings()
 	dss, err := config.NewDatabaseStore(getDsn(*sqlSettings.DriverName, *sqlSettings.DataSource))
 	require.NoError(t, err)

-	cStore, err := config.NewStoreFromBacking(dss)
+	cStore, err := config.NewStoreFromBacking(dss, customDefaults)
 	require.NoError(t, err)

 	return cStore, nil
@@ -133,18 +133,28 @@ func TestDatabaseStoreNew(t *testing.T) {
 	sqlSettings := mainHelper.GetSQLSettings()

 	t.Run("no existing configuration - initialization required", func(t *testing.T) {
-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

 		assert.Equal(t, "", *ds.Get().ServiceSettings.SiteURL)
 	})

+	t.Run("no existing configuration with custom defaults", func(t *testing.T) {
+		truncateTables(t)
+		ds, err := newTestDatabaseStore(t, customConfigDefaults)
+		require.NoError(t, err)
+		defer ds.Close()
+
+		assert.Equal(t, *customConfigDefaults.ServiceSettings.SiteURL, *ds.Get().ServiceSettings.SiteURL)
+		assert.Equal(t, *customConfigDefaults.DisplaySettings.ExperimentalTimezone, *ds.Get().DisplaySettings.ExperimentalTimezone)
+	})
+
 	t.Run("existing config, initialization required", func(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, testConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -152,11 +162,28 @@ func TestDatabaseStoreNew(t *testing.T) {
 		assertDatabaseNotEqualsConfig(t, testConfig)
 	})

+	t.Run("existing config with custom defaults, initialization required", func(t *testing.T) {
+		_, tearDown := setupConfigDatabase(t, testConfig, nil)
+		defer tearDown()
+
+		ds, err := newTestDatabaseStore(t, customConfigDefaults)
+		require.NoError(t, err)
+		defer ds.Close()
+
+		// already existing value should not be overwritten by the
+		// custom default value
+		assert.Equal(t, "http://TestStoreNew", *ds.Get().ServiceSettings.SiteURL)
+		// not existing value should be overwritten by the custom
+		// default value
+		assert.Equal(t, *customConfigDefaults.DisplaySettings.ExperimentalTimezone, *ds.Get().DisplaySettings.ExperimentalTimezone)
+		assertDatabaseNotEqualsConfig(t, testConfig)
+	})
+
 	t.Run("already minimally configured", func(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -164,6 +191,21 @@ func TestDatabaseStoreNew(t *testing.T) {
 		assertDatabaseEqualsConfig(t, minimalConfig)
 	})

+	t.Run("already minimally configured with custom defaults", func(t *testing.T) {
+		_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
+		defer tearDown()
+
+		ds, err := newTestDatabaseStore(t, customConfigDefaults)
+		require.NoError(t, err)
+		defer ds.Close()
+
+		// as the whole config has default values already, custom
+		// defaults should have no effect
+		assert.Equal(t, "http://minimal", *ds.Get().ServiceSettings.SiteURL)
+		assert.NotEqual(t, *customConfigDefaults.DisplaySettings.ExperimentalTimezone, *ds.Get().DisplaySettings.ExperimentalTimezone)
+		assertDatabaseEqualsConfig(t, minimalConfig)
+	})
+
 	t.Run("invalid url", func(t *testing.T) {
 		_, err := config.NewDatabaseStore("")
 		require.Error(t, err)
@@ -187,7 +229,7 @@ func TestDatabaseStoreGet(t *testing.T) {
 	_, tearDown := setupConfigDatabase(t, testConfig, nil)
 	defer tearDown()

-	ds, err := newTestDatabaseStore(t)
+	ds, err := newTestDatabaseStore(t, nil)
 	require.NoError(t, err)
 	defer ds.Close()

@@ -205,7 +247,7 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, testConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -215,7 +257,7 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		os.Setenv("MM_SERVICESETTINGS_SITEURL", "http://override")
 		defer os.Unsetenv("MM_SERVICESETTINGS_SITEURL")

-		ds, err = newTestDatabaseStore(t)
+		ds, err = newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -223,11 +265,34 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		assert.Equal(t, map[string]interface{}{"ServiceSettings": map[string]interface{}{"SiteURL": true}}, ds.GetEnvironmentOverrides())
 	})

+	t.Run("get override for a string variable with a custom default value", func(t *testing.T) {
+		_, tearDown := setupConfigDatabase(t, testConfig, nil)
+		defer tearDown()
+
+		ds, err := newTestDatabaseStore(t, customConfigDefaults)
+		require.NoError(t, err)
+		defer ds.Close()
+
+		assert.Equal(t, "http://TestStoreNew", *ds.Get().ServiceSettings.SiteURL)
+		assert.Empty(t, ds.GetEnvironmentOverrides())
+
+		os.Setenv("MM_SERVICESETTINGS_SITEURL", "http://override")
+		defer os.Unsetenv("MM_SERVICESETTINGS_SITEURL")
+
+		ds, err = newTestDatabaseStore(t, customConfigDefaults)
+		require.NoError(t, err)
+		defer ds.Close()
+
+		// environment override should take priority over the custom default value
+		assert.Equal(t, "http://override", *ds.Get().ServiceSettings.SiteURL)
+		assert.Equal(t, map[string]interface{}{"ServiceSettings": map[string]interface{}{"SiteURL": true}}, ds.GetEnvironmentOverrides())
+	})
+
 	t.Run("get override for a bool variable", func(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, testConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -237,7 +302,7 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		os.Setenv("MM_PLUGINSETTINGS_ENABLEUPLOADS", "true")
 		defer os.Unsetenv("MM_PLUGINSETTINGS_ENABLEUPLOADS")

-		ds, err = newTestDatabaseStore(t)
+		ds, err = newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -249,7 +314,7 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, testConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -259,7 +324,7 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		os.Setenv("MM_TEAMSETTINGS_MAXUSERSPERTEAM", "3000")
 		defer os.Unsetenv("MM_TEAMSETTINGS_MAXUSERSPERTEAM")

-		ds, err = newTestDatabaseStore(t)
+		ds, err = newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -271,7 +336,7 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, testConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -281,7 +346,7 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		os.Setenv("MM_SERVICESETTINGS_TLSSTRICTTRANSPORTMAXAGE", "123456")
 		defer os.Unsetenv("MM_SERVICESETTINGS_TLSSTRICTTRANSPORTMAXAGE")

-		ds, err = newTestDatabaseStore(t)
+		ds, err = newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -293,7 +358,7 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, testConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -303,7 +368,7 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		os.Setenv("MM_SQLSETTINGS_DATASOURCEREPLICAS", "user:pwd@db:5432/test-db")
 		defer os.Unsetenv("MM_SQLSETTINGS_DATASOURCEREPLICAS")

-		ds, err = newTestDatabaseStore(t)
+		ds, err = newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -318,7 +383,7 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, testConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -328,7 +393,7 @@ func TestDatabaseStoreGetEnivironmentOverrides(t *testing.T) {
 		os.Setenv("MM_SQLSETTINGS_DATASOURCEREPLICAS", "user:pwd@db:5432/test-db user:pwd@db2:5433/test-db2 user:pwd@db3:5434/test-db3")
 		defer os.Unsetenv("MM_SQLSETTINGS_DATASOURCEREPLICAS")

-		ds, err = newTestDatabaseStore(t)
+		ds, err = newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -348,7 +413,7 @@ func TestDatabaseStoreSet(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, emptyConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -362,7 +427,7 @@ func TestDatabaseStoreSet(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -378,7 +443,7 @@ func TestDatabaseStoreSet(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, ldapConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -395,7 +460,7 @@ func TestDatabaseStoreSet(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, emptyConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -414,7 +479,7 @@ func TestDatabaseStoreSet(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -433,7 +498,7 @@ func TestDatabaseStoreSet(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, readOnlyConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -453,7 +518,7 @@ func TestDatabaseStoreSet(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -476,7 +541,7 @@ func TestDatabaseStoreSet(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, emptyConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -501,7 +566,7 @@ func TestDatabaseStoreSet(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, emptyConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -518,7 +583,7 @@ func TestDatabaseStoreSet(t *testing.T) {
 		activeID, tearDown := setupConfigDatabase(t, emptyConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -549,7 +614,7 @@ func TestDatabaseStoreLoad(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, emptyConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -564,7 +629,7 @@ func TestDatabaseStoreLoad(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -586,7 +651,7 @@ func TestDatabaseStoreLoad(t *testing.T) {
 		os.Setenv("MM_SERVICESETTINGS_SITEURL", "http://overridePersistEnvVariables")
 		defer os.Unsetenv("MM_SERVICESETTINGS_SITEURL")

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -607,7 +672,7 @@ func TestDatabaseStoreLoad(t *testing.T) {
 		os.Setenv("MM_PLUGINSETTINGS_ENABLEUPLOADS", "true")
 		defer os.Unsetenv("MM_PLUGINSETTINGS_ENABLEUPLOADS")

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -630,7 +695,7 @@ func TestDatabaseStoreLoad(t *testing.T) {
 		os.Setenv("MM_TEAMSETTINGS_MAXUSERSPERTEAM", "3000")
 		defer os.Unsetenv("MM_TEAMSETTINGS_MAXUSERSPERTEAM")

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -653,7 +718,7 @@ func TestDatabaseStoreLoad(t *testing.T) {
 		os.Setenv("MM_SERVICESETTINGS_TLSSTRICTTRANSPORTMAXAGE", "123456")
 		defer os.Unsetenv("MM_SERVICESETTINGS_TLSSTRICTTRANSPORTMAXAGE")

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -676,7 +741,7 @@ func TestDatabaseStoreLoad(t *testing.T) {
 		os.Setenv("MM_SQLSETTINGS_DATASOURCEREPLICAS", "user:pwd@db:5432/test-db")
 		defer os.Unsetenv("MM_SQLSETTINGS_DATASOURCEREPLICAS")

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -701,7 +766,7 @@ func TestDatabaseStoreLoad(t *testing.T) {
 		os.Setenv("MM_SQLSETTINGS_DATASOURCEREPLICAS", "user:pwd@db:5432/test-db")
 		defer os.Unsetenv("MM_SQLSETTINGS_DATASOURCEREPLICAS")

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -721,7 +786,7 @@ func TestDatabaseStoreLoad(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, emptyConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -749,7 +814,7 @@ func TestDatabaseStoreLoad(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, fixesRequiredConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -763,7 +828,7 @@ func TestDatabaseStoreLoad(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, emptyConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -787,7 +852,7 @@ func TestDatabaseGetFile(t *testing.T) {
 	})
 	defer tearDown()

-	ds, err := newTestDatabaseStore(t)
+	ds, err := newTestDatabaseStore(t, nil)
 	require.NoError(t, err)
 	defer ds.Close()

@@ -818,7 +883,7 @@ func TestDatabaseSetFile(t *testing.T) {
 	_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
 	defer tearDown()

-	ds, err := newTestDatabaseStore(t)
+	ds, err := newTestDatabaseStore(t, nil)
 	require.NoError(t, err)
 	defer ds.Close()

@@ -871,7 +936,7 @@ func TestDatabaseHasFile(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -884,7 +949,7 @@ func TestDatabaseHasFile(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -902,7 +967,7 @@ func TestDatabaseHasFile(t *testing.T) {
 		})
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -915,7 +980,7 @@ func TestDatabaseHasFile(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -930,7 +995,7 @@ func TestDatabaseRemoveFile(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -942,7 +1007,7 @@ func TestDatabaseRemoveFile(t *testing.T) {
 		_, tearDown := setupConfigDatabase(t, minimalConfig, nil)
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -966,7 +1031,7 @@ func TestDatabaseRemoveFile(t *testing.T) {
 		})
 		defer tearDown()

-		ds, err := newTestDatabaseStore(t)
+		ds, err := newTestDatabaseStore(t, nil)
 		require.NoError(t, err)
 		defer ds.Close()

@@ -989,7 +1054,7 @@ func TestDatabaseStoreString(t *testing.T) {
 	_, tearDown := setupConfigDatabase(t, emptyConfig, nil)
 	defer tearDown()

-	ds, err := newTestDatabaseStore(t)
+	ds, err := newTestDatabaseStore(t, nil)
 	require.NoError(t, err)
 	require.NotNil(t, ds)
 	defer ds.Close()
--- a/config/file_test.go
+++ b/config/file_test.go
@@ -91,7 +91,7 @@ func TestFileStoreNew(t *testing.T) {

 		fs, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		configStore, err := config.NewStoreFromBacking(fs)
+		configStore, err := config.NewStoreFromBacking(fs, nil)
 		require.NoError(t, err)
 		defer configStore.Close()

@@ -99,13 +99,32 @@ func TestFileStoreNew(t *testing.T) {
 		assertFileNotEqualsConfig(t, testConfig, path)
 	})

+	t.Run("absolute path, initialization required, with custom defaults", func(t *testing.T) {
+		path, tearDown := setupConfigFile(t, testConfig)
+		defer tearDown()
+
+		fs, err := config.NewFileStore(path, false)
+		require.NoError(t, err)
+		configStore, err := config.NewStoreFromBacking(fs, customConfigDefaults)
+		require.NoError(t, err)
+		defer configStore.Close()
+
+		// already existing value should not be affected by the custom
+		// defaults
+		assert.Equal(t, "http://TestStoreNew", *configStore.Get().ServiceSettings.SiteURL)
+		// nonexisting value should be overwritten by the custom
+		// defaults
+		assert.Equal(t, *customConfigDefaults.DisplaySettings.ExperimentalTimezone, *configStore.Get().DisplaySettings.ExperimentalTimezone)
+		assertFileNotEqualsConfig(t, testConfig, path)
+	})
+
 	t.Run("absolute path, already minimally configured", func(t *testing.T) {
 		path, tearDown := setupConfigFile(t, minimalConfig)
 		defer tearDown()

 		fs, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		configStore, err := config.NewStoreFromBacking(fs)
+		configStore, err := config.NewStoreFromBacking(fs, nil)
 		require.NoError(t, err)
 		defer configStore.Close()

@@ -113,6 +132,23 @@ func TestFileStoreNew(t *testing.T) {
 		assertFileEqualsConfig(t, minimalConfig, path)
 	})

+	t.Run("absolute path, already minimally configured, with custom defaults", func(t *testing.T) {
+		path, tearDown := setupConfigFile(t, minimalConfig)
+		defer tearDown()
+
+		fs, err := config.NewFileStore(path, false)
+		require.NoError(t, err)
+		configStore, err := config.NewStoreFromBacking(fs, customConfigDefaults)
+		require.NoError(t, err)
+		defer configStore.Close()
+
+		// as the whole config has default values already, custom
+		// defaults should have no effect
+		assert.Equal(t, "http://minimal", *configStore.Get().ServiceSettings.SiteURL)
+		assert.NotEqual(t, *customConfigDefaults.DisplaySettings.ExperimentalTimezone, *configStore.Get().DisplaySettings.ExperimentalTimezone)
+		assertFileEqualsConfig(t, minimalConfig, path)
+	})
+
 	t.Run("absolute path, file does not exist", func(t *testing.T) {
 		_, tearDown := setupConfigFile(t, nil)
 		defer tearDown()
@@ -124,7 +160,7 @@ func TestFileStoreNew(t *testing.T) {
 		path := filepath.Join(tempDir, "does_not_exist")
 		fs, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		configStore, err := config.NewStoreFromBacking(fs)
+		configStore, err := config.NewStoreFromBacking(fs, nil)
 		require.NoError(t, err)
 		defer configStore.Close()

@@ -132,6 +168,25 @@ func TestFileStoreNew(t *testing.T) {
 		assertFileNotEqualsConfig(t, testConfig, path)
 	})

+	t.Run("absolute path, file does not exist, with custom defaults", func(t *testing.T) {
+		_, tearDown := setupConfigFile(t, nil)
+		defer tearDown()
+
+		tempDir, err := ioutil.TempDir("", "TestFileStoreNew")
+		require.NoError(t, err)
+		defer os.RemoveAll(tempDir)
+
+		path := filepath.Join(tempDir, "does_not_exist")
+		fs, err := config.NewFileStore(path, false)
+		require.NoError(t, err)
+		configStore, err := config.NewStoreFromBacking(fs, customConfigDefaults)
+		require.NoError(t, err)
+		defer configStore.Close()
+
+		assert.Equal(t, *customConfigDefaults.ServiceSettings.SiteURL, *configStore.Get().ServiceSettings.SiteURL)
+		assert.Equal(t, *customConfigDefaults.DisplaySettings.ExperimentalTimezone, *configStore.Get().DisplaySettings.ExperimentalTimezone)
+	})
+
 	t.Run("absolute path, path to file does not exist", func(t *testing.T) {
 		_, tearDown := setupConfigFile(t, nil)
 		defer tearDown()
@@ -143,7 +198,7 @@ func TestFileStoreNew(t *testing.T) {
 		path := filepath.Join(tempDir, "does/not/exist")
 		fs, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		configStore, err := config.NewStoreFromBacking(fs)
+		configStore, err := config.NewStoreFromBacking(fs, nil)
 		require.Nil(t, configStore)
 		require.Error(t, err)
 	})
@@ -165,7 +220,7 @@ func TestFileStoreNew(t *testing.T) {

 		fs, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		configStore, err := config.NewStoreFromBacking(fs)
+		configStore, err := config.NewStoreFromBacking(fs, nil)
 		require.NoError(t, err)
 		defer configStore.Close()

@@ -184,7 +239,7 @@ func TestFileStoreNew(t *testing.T) {
 		path := "TestFileStoreNew/a/b/c/config.json"
 		fs, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		configStore, err := config.NewStoreFromBacking(fs)
+		configStore, err := config.NewStoreFromBacking(fs, nil)
 		require.NoError(t, err)
 		defer configStore.Close()

@@ -199,7 +254,7 @@ func TestFileStoreGet(t *testing.T) {

 	fs, err := config.NewFileStore(path, false)
 	require.NoError(t, err)
-	configStore, err := config.NewStoreFromBacking(fs)
+	configStore, err := config.NewStoreFromBacking(fs, nil)
 	require.NoError(t, err)
 	defer configStore.Close()

@@ -225,7 +280,7 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -237,7 +292,7 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {

 		fsInner, err = config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err = config.NewStoreFromBacking(fsInner)
+		fs, err = config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -245,13 +300,40 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {
 		assert.Equal(t, map[string]interface{}{"ServiceSettings": map[string]interface{}{"SiteURL": true}}, fs.GetEnvironmentOverrides())
 	})

+	t.Run("get override for a string variable, with custom defaults", func(t *testing.T) {
+		path, tearDown := setupConfigFile(t, testConfig)
+		defer tearDown()
+
+		fsInner, err := config.NewFileStore(path, false)
+		require.NoError(t, err)
+		fs, err := config.NewStoreFromBacking(fsInner, customConfigDefaults)
+		require.NoError(t, err)
+		defer fs.Close()
+
+		assert.Equal(t, "http://TestStoreNew", *fs.Get().ServiceSettings.SiteURL)
+		assert.Empty(t, fs.GetEnvironmentOverrides())
+
+		os.Setenv("MM_SERVICESETTINGS_SITEURL", "http://override")
+		defer os.Unsetenv("MM_SERVICESETTINGS_SITEURL")
+
+		fsInner, err = config.NewFileStore(path, false)
+		require.NoError(t, err)
+		fs, err = config.NewStoreFromBacking(fsInner, customConfigDefaults)
+		require.NoError(t, err)
+		defer fs.Close()
+
+		// environment override should take priority over the custom default value
+		assert.Equal(t, "http://override", *fs.Get().ServiceSettings.SiteURL)
+		assert.Equal(t, map[string]interface{}{"ServiceSettings": map[string]interface{}{"SiteURL": true}}, fs.GetEnvironmentOverrides())
+	})
+
 	t.Run("get override for a bool variable", func(t *testing.T) {
 		path, tearDown := setupConfigFile(t, testConfig)
 		defer tearDown()

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -263,7 +345,7 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {

 		fsInner, err = config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err = config.NewStoreFromBacking(fsInner)
+		fs, err = config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -277,7 +359,7 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -289,7 +371,7 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {

 		fsInner, err = config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err = config.NewStoreFromBacking(fsInner)
+		fs, err = config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -303,7 +385,7 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -315,7 +397,7 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {

 		fsInner, err = config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err = config.NewStoreFromBacking(fsInner)
+		fs, err = config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -329,7 +411,7 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -341,7 +423,7 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {

 		fsInner, err = config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err = config.NewStoreFromBacking(fsInner)
+		fs, err = config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -358,7 +440,7 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -370,7 +452,7 @@ func TestFileStoreGetEnivironmentOverrides(t *testing.T) {

 		fsInner, err = config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err = config.NewStoreFromBacking(fsInner)
+		fs, err = config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -386,7 +468,7 @@ func TestFileStoreSet(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -407,7 +489,7 @@ func TestFileStoreSet(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -426,7 +508,7 @@ func TestFileStoreSet(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -447,7 +529,7 @@ func TestFileStoreSet(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -466,7 +548,7 @@ func TestFileStoreSet(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -488,7 +570,7 @@ func TestFileStoreSet(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -516,7 +598,7 @@ func TestFileStoreSet(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, true)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -548,7 +630,7 @@ func TestFileStoreLoad(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -565,7 +647,7 @@ func TestFileStoreLoad(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -589,7 +671,7 @@ func TestFileStoreLoad(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -614,7 +696,7 @@ func TestFileStoreLoad(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -639,7 +721,7 @@ func TestFileStoreLoad(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -664,7 +746,7 @@ func TestFileStoreLoad(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -689,7 +771,7 @@ func TestFileStoreLoad(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -716,7 +798,7 @@ func TestFileStoreLoad(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -738,7 +820,7 @@ func TestFileStoreLoad(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -759,7 +841,7 @@ func TestFileStoreLoad(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -778,7 +860,7 @@ func TestFileStoreLoad(t *testing.T) {

 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -808,7 +890,7 @@ func TestFileStoreWatcherEmitter(t *testing.T) {
 	t.Run("disabled", func(t *testing.T) {
 		fsInner, err := config.NewFileStore(path, false)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -832,7 +914,7 @@ func TestFileStoreWatcherEmitter(t *testing.T) {
 	t.Run("enabled", func(t *testing.T) {
 		fsInner, err := config.NewFileStore(path, true)
 		require.NoError(t, err)
-		fs, err := config.NewStoreFromBacking(fsInner)
+		fs, err := config.NewStoreFromBacking(fsInner, nil)
 		require.NoError(t, err)
 		defer fs.Close()

@@ -857,7 +939,7 @@ func TestFileStoreSave(t *testing.T) {

 	fsInner, err := config.NewFileStore(path, false)
 	require.NoError(t, err)
-	fs, err := config.NewStoreFromBacking(fsInner)
+	fs, err := config.NewStoreFromBacking(fsInner, nil)
 	require.NoError(t, err)
 	defer fs.Close()

--- a/config/migrate.go
+++ b/config/migrate.go
@@ -7,13 +7,13 @@ import "github.com/pkg/errors"

 // Migrate migrates SAML keys, certificates, and other config files from one store to another given their data source names.
 func Migrate(from, to string) error {
-	source, err := NewStore(from, false)
+	source, err := NewStore(from, false, nil)
 	if err != nil {
 		return errors.Wrapf(err, "failed to access source config %s", from)
 	}
 	defer source.Close()

-	destination, err := NewStore(to, false)
+	destination, err := NewStore(to, false, nil)
 	if err != nil {
 		return errors.Wrapf(err, "failed to access destination config %s", to)
 	}
--- a/config/migrate_test.go
+++ b/config/migrate_test.go
@@ -102,7 +102,7 @@ func TestMigrate(t *testing.T) {

 		sourcedb, err := config.NewDatabaseStore(sourceDSN)
 		require.NoError(t, err)
-		source, err := config.NewStoreFromBacking(sourcedb)
+		source, err := config.NewStoreFromBacking(sourcedb, nil)
 		require.NoError(t, err)
 		defer source.Close()

@@ -112,7 +112,7 @@ func TestMigrate(t *testing.T) {

 		destinationfile, err := config.NewFileStore(destinationDSN, false)
 		require.NoError(t, err)
-		destination, err := config.NewStoreFromBacking(destinationfile)
+		destination, err := config.NewStoreFromBacking(destinationfile, nil)
 		require.NoError(t, err)
 		defer destination.Close()

@@ -131,7 +131,7 @@ func TestMigrate(t *testing.T) {

 		sourcefile, err := config.NewFileStore(sourceDSN, false)
 		require.NoError(t, err)
-		source, err := config.NewStoreFromBacking(sourcefile)
+		source, err := config.NewStoreFromBacking(sourcefile, nil)
 		require.NoError(t, err)
 		defer source.Close()

@@ -141,7 +141,7 @@ func TestMigrate(t *testing.T) {

 		destinationdb, err := config.NewDatabaseStore(destinationDSN)
 		require.NoError(t, err)
-		destination, err := config.NewStoreFromBacking(destinationdb)
+		destination, err := config.NewStoreFromBacking(destinationdb, nil)
 		require.NoError(t, err)
 		defer destination.Close()

--- a/config/store.go
+++ b/config/store.go
@@ -48,19 +48,19 @@ type BackingStore interface {
 }

 // NewStore creates a database or file store given a data source name by which to connect.
-func NewStore(dsn string, watch bool) (*Store, error) {
+func NewStore(dsn string, watch bool, customDefaults *model.Config) (*Store, error) {
 	backingStore, err := getBackingStore(dsn, watch)
 	if err != nil {
 		return nil, err
 	}

-	return NewStoreFromBacking(backingStore)
-
+	return NewStoreFromBacking(backingStore, customDefaults)
 }

-func NewStoreFromBacking(backingStore BackingStore) (*Store, error) {
+func NewStoreFromBacking(backingStore BackingStore, customDefaults *model.Config) (*Store, error) {
 	store := &Store{
-		backingStore: backingStore,
+		backingStore:         backingStore,
+		configCustomDefaults: customDefaults,
 	}

 	if err := store.Load(); err != nil {
@@ -90,7 +90,7 @@ func NewTestMemoryStore() *Store {
 		panic("failed to initialize memory store: " + err.Error())
 	}

-	configStore, err := NewStoreFromBacking(memoryStore)
+	configStore, err := NewStoreFromBacking(memoryStore, nil)
 	if err != nil {
 		panic("failed to initialize config store: " + err.Error())
 	}
@@ -102,9 +102,10 @@ type Store struct {
 	emitter
 	backingStore BackingStore

-	configLock  sync.RWMutex
-	config      *model.Config
-	configNoEnv *model.Config
+	configLock           sync.RWMutex
+	config               *model.Config
+	configNoEnv          *model.Config
+	configCustomDefaults *model.Config

 	persistFeatureFlags bool
 }
@@ -195,6 +196,18 @@ func (s *Store) loadLockedWithOld(oldCfg *model.Config, unlockOnce *sync.Once) e
 		}
 	}

+	// If we have custom defaults set, the initial config is merged on
+	// top of them and we delete them not to be used again in the
+	// configuration reloads
+	if s.configCustomDefaults != nil {
+		var mErr error
+		loadedConfig, mErr = Merge(s.configCustomDefaults, loadedConfig, nil)
+		if mErr != nil {
+			return errors.Wrap(mErr, "failed to merge custom config defaults")
+		}
+		s.configCustomDefaults = nil
+	}
+
 	loadedConfig.SetDefaults()

 	s.configNoEnv = loadedConfig.Clone()
--- a/config/store_test.go
+++ b/config/store_test.go
@@ -28,25 +28,25 @@ func TestNewStore(t *testing.T) {
 	require.NoError(t, os.Mkdir(filepath.Join(tempDir, "config"), 0700))

 	t.Run("database dsn", func(t *testing.T) {
-		ds, err := config.NewStore(getDsn(*sqlSettings.DriverName, *sqlSettings.DataSource), false)
+		ds, err := config.NewStore(getDsn(*sqlSettings.DriverName, *sqlSettings.DataSource), false, nil)
 		require.NoError(t, err)
 		ds.Close()
 	})

 	t.Run("database dsn, watch ignored", func(t *testing.T) {
-		ds, err := config.NewStore(getDsn(*sqlSettings.DriverName, *sqlSettings.DataSource), true)
+		ds, err := config.NewStore(getDsn(*sqlSettings.DriverName, *sqlSettings.DataSource), true, nil)
 		require.NoError(t, err)
 		ds.Close()
 	})

 	t.Run("file dsn", func(t *testing.T) {
-		fs, err := config.NewStore("config.json", false)
+		fs, err := config.NewStore("config.json", false, nil)
 		require.NoError(t, err)
 		fs.Close()
 	})

 	t.Run("file dsn, watch", func(t *testing.T) {
-		fs, err := config.NewStore("config.json", true)
+		fs, err := config.NewStore("config.json", true, nil)
 		require.NoError(t, err)
 		fs.Close()
 	})
--- a/services/mailservice/mail_test.go
+++ b/services/mailservice/mail_test.go
@@ -129,7 +129,7 @@ func TestSendMailUsingConfig(t *testing.T) {

 	fsInner, err := config.NewFileStore("config.json", false)
 	require.Nil(t, err)
-	fs, err := config.NewStoreFromBacking(fsInner)
+	fs, err := config.NewStoreFromBacking(fsInner, nil)
 	require.Nil(t, err)

 	cfg := fs.Get()
@@ -170,7 +170,7 @@ func TestSendMailWithEmbeddedFilesUsingConfig(t *testing.T) {

 	fsInner, err := config.NewFileStore("config.json", false)
 	require.Nil(t, err)
-	fs, err := config.NewStoreFromBacking(fsInner)
+	fs, err := config.NewStoreFromBacking(fsInner, nil)
 	require.Nil(t, err)

 	cfg := fs.Get()
@@ -217,7 +217,7 @@ func TestSendMailUsingConfigAdvanced(t *testing.T) {

 	fsInner, err := config.NewFileStore("config.json", false)
 	require.Nil(t, err)
-	fs, err := config.NewStoreFromBacking(fsInner)
+	fs, err := config.NewStoreFromBacking(fsInner, nil)
 	require.Nil(t, err)

 	cfg := fs.Get()