The internet. The gift that keeps on giving.
> On Nov 3, 2023, at 7:54 AM, Al Corona <alvarocorona1...@gmail.com> wrote:
>
> Off topic question. But does anyone know how I can gain admin access on my
> work computer?
>
>> On Thursday, June 29, 2017 at 12:01:16 AM UTC-7 Kai Zhang wrote:
>> Go version 1.8.3
>>
>> In DB.QueryContext(), Go will close long live connection which exceeded the
>> duration setted by DB.SetConnMaxLifetime(), the code is below
>> database/sql/sql.go
>> 895 func (db *DB) conn(ctx context.Context, strategy connReuseStrategy)
>> (*driverConn, error) {
>> 896 db.mu.Lock()
>> 897 if db.closed {
>> 898 db.mu.Unlock()
>> 899 return nil, errDBClosed
>> 900 }
>> 901 // Check if the context is expired.
>> 902 select {
>> 903 default:
>> 904 case <-ctx.Done():
>> 905 db.mu.Unlock()
>> 906 return nil, ctx.Err()
>> 907 }
>> 908 lifetime := db.maxLifetime
>> 909
>> 910 // Prefer a free connection, if possible.
>> 911 numFree := len(db.freeConn)
>> 912 if strategy == cachedOrNewConn && numFree > 0 {
>> 913 conn := db.freeConn[0]
>> 914 copy(db.freeConn, db.freeConn[1:])
>> 915 db.freeConn = db.freeConn[:numFree-1]
>> 916 conn.inUse = true
>> 917 db.mu.Unlock()
>> 918 if conn.expired(lifetime) {
>> 919 conn.Close()
>> 920 return nil, driver.ErrBadConn
>> 921 }
>>
>>
>> 922 return conn, nil
>> 923 }
>>
>>
>> The problem is if driver.Close() has some handshake to tear down the
>> connection, this may introduce unexpected latency. But the driver.Conn
>> interface not mention this.
>> database/sql/driver/driver.go
>> 143 type Conn interface {
>> 144 // Prepare returns a prepared statement, bound to this connection.
>> 145 Prepare(query string) (Stmt, error)
>> 146
>> 147 // Close invalidates and potentially stops any current
>> 148 // prepared statements and transactions, marking this
>> 149 // connection as no longer in use.
>> 150 //
>> 151 // Because the sql package maintains a free pool of
>> 152 // connections and only calls Close when there's a surplus of
>> 153 // idle connections, it shouldn't be necessary for drivers to
>> 154 // do their own connection caching.
>>
>>
>> 155 Close() error
>> 156
>> 157 // Begin starts and returns a new transaction.
>> 158 //
>> 159 // Deprecated: Drivers should implement ConnBeginTx instead (or
>> additionally).
>> 160 Begin() (Tx, error)
>> 161 }
>>
>> There is already a goroutine to clean the connections, why still need a
>> synchronous check?
>> database/sql/sql.go
>> 750 func (db *DB) connectionCleaner(d time.Duration) {
>>
>>
>> 751 const minInterval = time.Second
>> 752
>> 753 if d < minInterval {
>> 754 d = minInterval
>> 755 }
>> 756 t := time.NewTimer(d)
>> 757
>> 758 for {
>> 759 select {
>> 760 case <-t.C:
>> 761 case <-db.cleanerCh: // maxLifetime was changed or db was
>> closed.
>> 762 }
>> 763
>> 764 db.mu.Lock()
>> 765 d = db.maxLifetime
>> 766 if db.closed || db.numOpen == 0 || d <= 0 {
>> 767 db.cleanerCh = nil
>> 768 db.mu.Unlock()
>> 769 return
>> 770 }
>> 771
>> 772 expiredSince := nowFunc().Add(-d)
>> 773 var closing []*driverConn
>> 774 for i := 0; i < len(db.freeConn); i++ {
>> 775 c := db.freeConn[i]
>> 776 if c.createdAt.Before(expiredSince) {
>> 777 closing = append(closing, c)
>> 778 last := len(db.freeConn) - 1
>> 779 db.freeConn[i] = db.freeConn[last]
>> 780 db.freeConn[last] = nil
>> 781 db.freeConn = db.freeConn[:last]
>> 782 i--
>> 783 }
>> 784 }
>>
>>
>>
>> Is this by design or need to be fixed?
>
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