fix #1622

Allow users to set max MySQL connections and connection lifetime;
set a sane default for max connections if it's not present.

irc/mysql/config.go

@@ -17,6 +17,8 @@ type Config struct {
 	Password        string
 	HistoryDatabase string `yaml:"history-database"`
 	Timeout         time.Duration
+	MaxConns        int           `yaml:"max-conns"`
+	ConnMaxLifetime time.Duration `yaml:"conn-max-lifetime"`
 
 	// XXX these are copied from elsewhere in the config:
 	ExpireTime           time.Duration

irc/mysql/history.go

@@ -100,6 +100,14 @@ func (m *MySQL) Open() (err error) {
 		return err
 	}
 
+	if m.config.MaxConns != 0 {
+		m.db.SetMaxOpenConns(m.config.MaxConns)
+		m.db.SetMaxIdleConns(m.config.MaxConns)
+	}
+	if m.config.ConnMaxLifetime != 0 {
+		m.db.SetConnMaxLifetime(m.config.ConnMaxLifetime)
+	}
+
 	err = m.fixSchemas()
 	if err != nil {
 		return err