Will connections be leaked when use transactions?

[kof02guy]

Issue description

I used DB.Begin() to start a transaction and DB.Commit() or DB.Rollback() to end transaction, but I found some connections in the status of "SLEEP" for quite a long time (> 2 hours). And this is not expected. So do I miss something to make sure the connections are all to be freed?

Example code

mgr.statsConn, err = sql.Open("mysql", statsConnStr)
......
tx, err := mgr.statsConn.Begin()
if err != nil {
LogError(FAIL_CRITICAL, DB, "Begin transaction failed:%v", err)
return err
}
defer tx.Rollback()
...
multiple Exec clauses just like:
rst, err = tx.Exec(sqlStr)
if err != nil {
LogInfo("Update xxx error. Sql:%s, Error:%v", sqlStr, err)
return err
}
...
if err = tx.Commit(); nil != err {
LogError(FAIL_CRITICAL, DB, "Commit error:%v", err)
return err
}

sql.Open() will be called only once of the entire lifetime of the process. and mgr.statsConn will be used everytime when opening a transaction
I'm wondering the right position for the tx.Rollback(). If error happens, is it necessary to call tx.Rollback()? Will tx be non-nill then?

Error log

If you have an error log, please paste it here.

Configuration

Driver version (or git SHA):

Go version: run go version in your console
1.7.5

Server version: E.g. MySQL 5.6, MariaDB 10.0.20
MYSQL 5.5.37-enterprise-commercial-advanced-log

Server OS: E.g. Debian 8.1 (Jessie), Windows 10

[busyfree]

@kof02guy I have the same problem with mysql connection socket leak, I don't know what's the reason to occured this problem. see #707

from wait_closed to can't identify protocol

[methane]

tx.Commit() and Rollback() returns connection to the pool.

I recommend DB.SetConnMaxLifetime(time.Second * 10) for everyone except experts
who can solve problem by themselves.