Unified Storage: Fix Create, Update and Delete wrt Resource Versions (#88183)

* add sqltemplate utilities, improve tests and documentation

* bunch of things

* remove unnecessary message

* add queries

* add queries

* add queries

* add folders support

* fix diff

* fix linters

* fix diff

* fix linters

* fix linters

* fix typo

* fix linters

* fix linters

* fix linters

* several fixes

* several fixes

* temporarily disable k8s integration tests for Entity Server

* postpone some tests

* postpone documentation changes

* Fix bug in create

* improve error reporting

* fix PostgeSQL parameters

* fix MySQL sqlmode

* fix MySQL-5.7

* reduce but document the number of database connection options

* remove unused code and improve docs

pkg/services/store/entity/db/dbimpl/dbimpl.go

@@ -2,6 +2,7 @@ package dbimpl
 
 import (
 	"fmt"
+	"sync"
 
 	"github.com/dlmiddlecote/sqlstats"
 	"github.com/jmoiron/sqlx"
@@ -31,6 +32,9 @@ func ProvideEntityDB(db db.DB, cfg *setting.Cfg, features featuremgmt.FeatureTog
 }
 
 type EntityDB struct {
+	once    sync.Once
+	onceErr error
+
 	db       db.DB
 	features featuremgmt.FeatureToggles
 	engine   *xorm.Engine
@@ -45,42 +49,57 @@ func (db *EntityDB) Init() error {
 }
 
 func (db *EntityDB) GetEngine() (*xorm.Engine, error) {
+	db.once.Do(func() {
+		db.onceErr = db.init()
+	})
+
+	return db.engine, db.onceErr
+}
+
+func (db *EntityDB) init() error {
 	if db.engine != nil {
-		return db.engine, nil
+		return nil
 	}
 
 	var engine *xorm.Engine
 	var err error
 
-	cfgSection := db.cfg.SectionWithEnvOverrides("entity_api")
-	dbType := cfgSection.Key("db_type").MustString("")
+	getter := &sectionGetter{
+		DynamicSection: db.cfg.SectionWithEnvOverrides("entity_api"),
+	}
+
+	dbType := getter.Key("db_type").MustString("")
 
 	// if explicit connection settings are provided, use them
 	if dbType != "" {
 		if dbType == "postgres" {
-			engine, err = getEnginePostgres(cfgSection, db.tracer)
+			engine, err = getEnginePostgres(getter, db.tracer)
 			if err != nil {
-				return nil, err
+				return err
 			}
 
 			// FIXME: this config option is cockroachdb-specific, it's not supported by postgres
+			// FIXME: this only sets this option for the session that we get
+			// from the pool right now. A *sql.DB is a pool of connections,
+			// there is no guarantee that the session where this is run will be
+			// the same where we need to change the type of a column
 			_, err = engine.Exec("SET SESSION enable_experimental_alter_column_type_general=true")
 			if err != nil {
 				db.log.Error("error connecting to postgres", "msg", err.Error())
 				// FIXME: return nil, err
 			}
 		} else if dbType == "mysql" {
-			engine, err = getEngineMySQL(cfgSection, db.tracer)
+			engine, err = getEngineMySQL(getter, db.tracer)
 			if err != nil {
-				return nil, err
+				return err
 			}
-			_, err = engine.Exec("SELECT 1")
-			if err != nil {
-				return nil, err
+
+			if err = engine.Ping(); err != nil {
+				return err
 			}
 		} else {
 			// TODO: sqlite support
-			return nil, fmt.Errorf("invalid db type specified: %s", dbType)
+			return fmt.Errorf("invalid db type specified: %s", dbType)
 		}
 
 		// register sql stat metrics
@@ -89,7 +108,7 @@ func (db *EntityDB) GetEngine() (*xorm.Engine, error) {
 		}
 
 		// configure sql logging
-		debugSQL := cfgSection.Key("log_queries").MustBool(false)
+		debugSQL := getter.Key("log_queries").MustBool(false)
 		if !debugSQL {
 			engine.SetLogger(&xorm.DiscardLogger{})
 		} else {
@@ -98,10 +117,11 @@ func (db *EntityDB) GetEngine() (*xorm.Engine, error) {
 			engine.ShowSQL(true)
 			engine.ShowExecTime(true)
 		}
+
 		// otherwise, try to use the grafana db connection
 	} else {
 		if db.db == nil {
-			return nil, fmt.Errorf("no db connection provided")
+			return fmt.Errorf("no db connection provided")
 		}
 
 		engine = db.db.GetEngine()
@@ -109,12 +129,12 @@ func (db *EntityDB) GetEngine() (*xorm.Engine, error) {
 
 	db.engine = engine
 
-	if err := migrations.MigrateEntityStore(db, db.features); err != nil {
+	if err := migrations.MigrateEntityStore(engine, db.cfg, db.features); err != nil {
 		db.engine = nil
-		return nil, err
+		return fmt.Errorf("run migrations: %w", err)
 	}
 
-	return db.engine, nil
+	return nil
 }
 
 func (db *EntityDB) GetSession() (*session.SessionDB, error) {