[wip] cleanup unused connections

Signed-off-by: Anton Nesterov <anton@demiurg.io>

pkg/adapter/DBAdapter.go

@@ -10,61 +10,93 @@ import (
  * DBAdapter
  * Automatically creates connections for each database URL.
  * Executes queries on the specified database.
- * TODO: Closes connections older than 2 minutes.
+ * Closes connections older than ConnectionLiveTime
 **/
 type DBAdapter struct {
-	Type              string
-	MaxAttempts       int
-	_db               map[string]*sql.DB
-	_connect_attempts map[string]int
-	_connect_time     map[string]int64
+	Type               string
+	MaxAttempts        int
+	ConnectionLiveTime int
+	dbs                *DBMap
+}
+
+type DBMap struct {
+	Connections        map[string]*sql.DB
+	ConnectionAttempts map[string]int
+	ConnectionTime     map[string]int64
 }
 
 func (a *DBAdapter) Open(url string) (*sql.DB, error) {
-	if a._db == nil {
-		a._db = make(map[string]*sql.DB)
-	}
-	if a._connect_attempts == nil {
-		a._connect_attempts = make(map[string]int)
-	}
-	if a._connect_time == nil {
-		a._connect_time = make(map[string]int64)
-	}
+	defer a.CleanUp()
+
 	if a.MaxAttempts == 0 {
 		a.MaxAttempts = 6
 	}
-	if _, ok := a._db[url]; !ok {
-		a._db[url], _ = sql.Open(a.Type, url)
+	if a.ConnectionLiveTime == 0 {
+		a.ConnectionLiveTime = 120
+	}
+	if a.dbs == nil {
+		a.dbs = &DBMap{
+			Connections:        make(map[string]*sql.DB),
+			ConnectionAttempts: make(map[string]int),
+			ConnectionTime:     make(map[string]int64),
+		}
+	}
+
+	connections := a.dbs.Connections
+	attempts := a.dbs.ConnectionAttempts
+	lastHits := a.dbs.ConnectionTime
+
+	lastHits[url] = time.Now().Unix()
+	if _, ok := connections[url]; !ok {
+		connections[url], _ = sql.Open(a.Type, url)
 	} else {
-		err := a._db[url].Ping()
+		err := connections[url].Ping()
 		if err != nil {
-			a._db[url] = nil
-			a._connect_attempts[url]++
+			connections[url] = nil
+			attempts[url]++
 			time.Sleep(time.Duration(5) * time.Second)
-			if a._connect_attempts[url] > a.MaxAttempts {
-				return nil, fmt.Errorf(`failed to connect to "%s"`, url)
+			if attempts[url] > a.MaxAttempts {
+				return nil, fmt.Errorf(
+					`failed to connect to "%s", after %v attempts`,
+					url,
+					a.MaxAttempts,
+				)
 			}
 			return a.Open(url)
 		}
 	}
-	a._connect_attempts[url] = 0
-	a._connect_time[url] = time.Now().Unix()
-	return a._db[url], nil
+	a.dbs.ConnectionAttempts[url] = 0
+	return a.dbs.Connections[url], nil
 }
 
 func (a *DBAdapter) GetDB(url string) *sql.DB {
-	if a._db == nil {
+	if a.dbs == nil {
 		return nil
 	}
-	return a._db[url]
+	return a.dbs.Connections[url]
 }
 
 func (a *DBAdapter) Close() {
-	for _, db := range a._db {
+	for _, db := range a.dbs.Connections {
 		db.Close()
 	}
-	a._db = nil
-	a._connect_attempts = nil
+	a.dbs = nil
+}
+
+func (a *DBAdapter) CleanUp() {
+	if a.dbs == nil {
+		return
+	}
+	lastHits := a.dbs.ConnectionTime
+	liveTime := a.ConnectionLiveTime
+	for url, db := range a.dbs.Connections {
+		if time.Now().Unix()-lastHits[url] > int64(liveTime) {
+			db.Close()
+			delete(a.dbs.Connections, url)
+			delete(a.dbs.ConnectionAttempts, url)
+			delete(a.dbs.ConnectionTime, url)
+		}
+	}
 }
 
 func (a *DBAdapter) Query(req Query) (*sql.Rows, error) {