Database/sql Tx - detecting Commit or Rollback

Managing errors and panics - Keep your guard up!

In transaction management, being diligent about handling both errors and panics is essential. Here's what you need do:

• defer is your time-lapse guardian angel. Enlist its help to ensure tx.Rollback() and tx.Commit() are called no matter what comes swinging!
• Employ recover() within defer to swoop in and catch any thrown panic and immediately initiate a Rollback.
• error is moody, always inspect its state returned by Commit() and Rollback().

Procedure for Commit and Rollback - The Step-by-Step Dance

• Set up defer to Rollback initially, but hang on! If Commit is successful, we skip over this step!
• Protect tx.Commit() with an error-checking armor. If err guards are down (is nil), Commit can pass through!

defer func() {
    if err != nil {
        if rbErr := ts.Rollback(); rbErr != nil {
            log.Fatalf("tx.Rollback just failed miserably: %v", rbErr)
        }
    }
}()

// Magic happens here...
if err = tx.Commit(); err != nil {
    // Handle err
}


• If err wears the cloak of mystery (is not nil), don't let Rollback steal err's identity after a failed Commit.

if err = tx.Commit(); err != nil {
    log.Printf("Failed to commit! It's not you, it's me: %v", err)
    if rbErr := tx.Rollback(); rbErr != nil && err == nil {
        err = rbErr
    }
}


• Lean back and relax! Uncommitted transactions are ruthlessly rolled back by the database on Tx close.

Streamlining with a transaction handler - The Puppet Master

Strive for simplicity by encapsulating Commit or Rollback handling within an all-knowing helper, a 'transaction handler':

func withTransaction(db *sql.DB, fn func(*TxStatus) error) error {
    tx, err := db.Begin()
    if err != nil {
        return err
    }
    
    ts := &TxStatus{Tx: tx}
    err = fn(ts)
    
    if err != nil {
        ts.Rollback() // Oops, something went horribly wrong
        return err
    }
    return ts.Commit() // All systems go!
}


This allows you to perform operations within a transaction without worrying about Commit or Rollback specifics — withTransaction expertly handles it for you.

Common Missteps - What not to do!

To achieve an Oscar-winning transaction management performance, beware of these common pitfalls:

Conditional Rollback complexity

Plenty of action in defer that handles transaction Rollback can lead to a convoluted plot. Simplicity is king — stick to it.

The villain of shadows - Error shadowing

Don't let the villain secretly swap places with someone else! This can happen unnoticed in error handling within the defer closure, beware!

Transaction leaks - Sneaky Retreats

Be watchful! If a function that owns the transaction makes an early exit without ensuring the transaction is committed or rolled back, it may lead to database resource leaks.

Unchecked Rollback errors - The Invisible Enemy

Overlooking errors from Rollback() can spell disaster as they can indicate issues with resource cleanup or potentially even data corruption. Handle them!