Expose sql.DB's SetConnMaxLifetime in settings (#144)

When using a database server that closes inactive connections after some
duration, set `SQLConnMaxLifetime` to a value less than that duration.
Otherwise, the connection will be reused forever, and this could result in a
dropped connection.

For example, if you are using MySQL configured with `wait_timeout = 28800`, use
something like `SQLConnMaxLifetime=14400s`.

Refs #139

Author: mgatny

config/configuration.go

@@ -18,5 +18,6 @@ const (
 	FileStorePath            string = "FileStorePath"
 	SQLDriver                string = "SQLDriver"
 	SQLDataSourceName        string = "SQLDataSourceName"
+	SQLConnMaxLifetime       string = "SQLConnMaxLifetime"
 	ValidateFieldsOutOfOrder string = "ValidateFieldsOutOfOrder"
 )

config/doc.go

@@ -138,5 +138,15 @@ The name of the database driver to use (see https://github.com/golang/go/wiki/SQ
 SQLDataSourceName
 
 The driver-specific data source name of the database to use.  Only used with SqlStoreFactory.
+
+SQLConnMaxLifetime
+
+SetConnMaxLifetime sets the maximum duration of time that a database connection may be reused (see https://golang.org/pkg/database/sql/#DB.SetConnMaxLifetime).  Defaults to zero, which causes connections to be reused forever.  Only used with SqlStoreFactory.
+
+If your database server has a config option to close inactive connections after some duration (e.g. MySQL "wait_timeout"), set SQLConnMaxLifetime to a value less than that duration.
+
+Example Values:
+ SQLConnMaxLifetime=14400s # 14400 seconds
+ SQLConnMaxLifetime=2h45m  # 2 hours and 45 minutes
 */
 package config

session_settings.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"strconv"
+	"time"
 )
 
 //SessionSettings maps session settings to values with typed accessors.
@@ -61,6 +62,17 @@ func (s *SessionSettings) IntSetting(setting string) (int, error) {
 	return strconv.Atoi(stringVal)
 }
 
+//DurationSetting returns the requested setting parsed as a time.Duration.  Returns an error if the setting is not set or cannot be parsed as a time.Duration.
+func (s *SessionSettings) DurationSetting(setting string) (val time.Duration, err error) {
+	stringVal, err := s.Setting(setting)
+
+	if err != nil {
+		return
+	}
+
+	return time.ParseDuration(stringVal)
+}
+
 //BoolSetting returns the requested setting parsed as a boolean.  Returns an errror if the setting is not set or cannot be parsed as a bool.
 func (s SessionSettings) BoolSetting(setting string) (bool, error) {
 	stringVal, err := s.Setting(setting)

sqlstore.go

@@ -13,11 +13,12 @@ type sqlStoreFactory struct {
 }
 
 type sqlStore struct {
-	sessionID         SessionID
-	cache             *memoryStore
-	sqlDriver         string
-	sqlDataSourceName string
-	db                *sql.DB
+	sessionID          SessionID
+	cache              *memoryStore
+	sqlDriver          string
+	sqlDataSourceName  string
+	sqlConnMaxLifetime time.Duration
+	db                 *sql.DB
 }
 
 // NewSQLStoreFactory returns a sql-based implementation of MessageStoreFactory
@@ -39,21 +40,31 @@ func (f sqlStoreFactory) Create(sessionID SessionID) (msgStore MessageStore, err
 	if err != nil {
 		return nil, err
 	}
-	return newSQLStore(sessionID, sqlDriver, sqlDataSourceName)
+	sqlConnMaxLifetime := 0 * time.Second
+	if sessionSettings.HasSetting(config.SQLConnMaxLifetime) {
+		sqlConnMaxLifetime, err = sessionSettings.DurationSetting(config.SQLConnMaxLifetime)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return newSQLStore(sessionID, sqlDriver, sqlDataSourceName, sqlConnMaxLifetime)
 }
 
-func newSQLStore(sessionID SessionID, driver string, dataSourceName string) (store *sqlStore, err error) {
+func newSQLStore(sessionID SessionID, driver string, dataSourceName string, connMaxLifetime time.Duration) (store *sqlStore, err error) {
 	store = &sqlStore{
-		sessionID:         sessionID,
-		cache:             &memoryStore{},
-		sqlDriver:         driver,
-		sqlDataSourceName: dataSourceName,
+		sessionID:          sessionID,
+		cache:              &memoryStore{},
+		sqlDriver:          driver,
+		sqlDataSourceName:  dataSourceName,
+		sqlConnMaxLifetime: connMaxLifetime,
 	}
 	store.cache.Reset()
 
 	if store.db, err = sql.Open(store.sqlDriver, store.sqlDataSourceName); err != nil {
 		return nil, err
 	}
+	store.db.SetConnMaxLifetime(store.sqlConnMaxLifetime)
+
 	if err = store.db.Ping(); err != nil { // ensure immediate connection
 		return nil, err
 	}

sqlstore_test.go

@@ -47,6 +47,7 @@ func (suite *SQLStoreTestSuite) SetupTest() {
 [DEFAULT]
 SQLDriver=%s
 SQLDataSourceName=%s
+SQLConnMaxLifetime=14400s
 
 [SESSION]
 BeginString=%s