MM-11262: database config store (#10281)

* vendor github.com/jmoiron/sqlx

* MM-11262: introduce a database store

* revert unnecessary fmt.Errorf

* simplify unit test helper methods

* remote TODO re: retry

* relocate initializeConfigurationsTable for clarity

* factor out a commonStore

* acquire database config lock on close for safety

* add missing header

* fix lock comment

config/file.go

@@ -10,7 +10,6 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
-	"sync"
 
 	"github.com/pkg/errors"
 
@@ -25,14 +24,11 @@ var (
 
 // FileStore is a config store backed by a file such as config/config.json.
 type FileStore struct {
-	emitter
+	commonStore
 
-	config               *model.Config
-	environmentOverrides map[string]interface{}
-	configLock           sync.RWMutex
-	path                 string
-	watch                bool
-	watcher              *watcher
+	path    string
+	watch   bool
+	watcher *watcher
 }
 
 // NewFileStore creates a new instance of a config store backed by the given file path.
@@ -90,68 +86,15 @@ func resolveConfigFilePath(path string) (string, error) {
 	return "", fmt.Errorf("failed to find config file %s", path)
 }
 
-// Get fetches the current, cached configuration.
-func (fs *FileStore) Get() *model.Config {
-	fs.configLock.RLock()
-	defer fs.configLock.RUnlock()
-
-	return fs.config
-}
-
-// GetEnvironmentOverrides fetches the configuration fields overridden by environment variables.
-func (fs *FileStore) GetEnvironmentOverrides() map[string]interface{} {
-	fs.configLock.RLock()
-	defer fs.configLock.RUnlock()
-
-	return fs.environmentOverrides
-}
-
 // Set replaces the current configuration in its entirety, without updating the backing store.
 func (fs *FileStore) Set(newCfg *model.Config) (*model.Config, error) {
-	fs.configLock.Lock()
-	var unlockOnce sync.Once
-	defer unlockOnce.Do(fs.configLock.Unlock)
+	return fs.commonStore.set(newCfg, func(cfg *model.Config) error {
+		if *fs.config.ClusterSettings.Enable && *fs.config.ClusterSettings.ReadOnlyConfig {
+			return ErrReadOnlyConfiguration
+		}
 
-	oldCfg := fs.config
-
-	// TODO: disallow attempting to save a directly modified config (comparing pointers). This
-	// wouldn't be an exhaustive check, given the use of pointers throughout the data
-	// structure, but might prevent common mistakes. Requires upstream changes first.
-	// if newCfg == oldCfg {
-	// 	return nil, errors.New("old configuration modified instead of cloning")
-	// }
-
-	newCfg = newCfg.Clone()
-	newCfg.SetDefaults()
-
-	// Sometimes the config is received with "fake" data in sensitive fields. Apply the real
-	// data from the existing config as necessary.
-	desanitize(oldCfg, newCfg)
-
-	if err := newCfg.IsValid(); err != nil {
-		return nil, errors.Wrap(err, "new configuration is invalid")
-	}
-
-	if *oldCfg.ClusterSettings.Enable && *oldCfg.ClusterSettings.ReadOnlyConfig {
-		return nil, ErrReadOnlyConfiguration
-	}
-
-	// Ideally, Set would persist automatically and abstract this completely away from the
-	// client. Doing so requires a few upstream changes first, so for now an explicit Save()
-	// remains required.
-	// if err := fs.persist(newCfg); err != nil {
-	// 	return nil, errors.Wrap(err, "failed to persist")
-	// }
-
-	fs.config = newCfg
-
-	unlockOnce.Do(fs.configLock.Unlock)
-
-	// Notify listeners synchronously. Ideally, this would be asynchronous, but existing code
-	// assumes this and there would be increased complexity to avoid racing updates.
-	fs.invokeConfigListeners(oldCfg, newCfg)
-
-	return oldCfg, nil
+		return nil
+	})
 }
 
 // persist writes the configuration to the configured file.
@@ -206,50 +149,7 @@ func (fs *FileStore) Load() (err error) {
 		}
 	}()
 
-	allowEnvironmentOverrides := true
-	loadedCfg, environmentOverrides, err := unmarshalConfig(f, allowEnvironmentOverrides)
-	if err != nil {
-		return errors.Wrapf(err, "failed to unmarshal config from %s", fs.path)
-	}
-
-	// SetDefaults generates various keys and salts if not previously configured. Determine if
-	// such a change will be made before invoking. This method will not effect the save: that
-	// remains the responsibility of the caller.
-	needsSave = needsSave || loadedCfg.SqlSettings.AtRestEncryptKey == nil || len(*loadedCfg.SqlSettings.AtRestEncryptKey) == 0
-	needsSave = needsSave || loadedCfg.FileSettings.PublicLinkSalt == nil || len(*loadedCfg.FileSettings.PublicLinkSalt) == 0
-	needsSave = needsSave || loadedCfg.EmailSettings.InviteSalt == nil || len(*loadedCfg.EmailSettings.InviteSalt) == 0
-
-	loadedCfg.SetDefaults()
-
-	if err := loadedCfg.IsValid(); err != nil {
-		return errors.Wrap(err, "invalid config")
-	}
-
-	if changed := fixConfig(loadedCfg); changed {
-		needsSave = true
-	}
-
-	fs.configLock.Lock()
-	var unlockOnce sync.Once
-	defer unlockOnce.Do(fs.configLock.Unlock)
-
-	if needsSave {
-		if err = fs.persist(loadedCfg); err != nil {
-			return errors.Wrap(err, "failed to persist required changes after load")
-		}
-	}
-
-	oldCfg := fs.config
-	fs.config = loadedCfg
-	fs.environmentOverrides = environmentOverrides
-
-	unlockOnce.Do(fs.configLock.Unlock)
-
-	// Notify listeners synchronously. Ideally, this would be asynchronous, but existing code
-	// assumes this and there would be increased complexity to avoid racing updates.
-	fs.invokeConfigListeners(oldCfg, loadedCfg)
-
-	return nil
+	return fs.commonStore.load(f, needsSave, fs.persist)
 }
 
 // Save writes the current configuration to the backing store.