Go Mongodb Transaction

In this tutorial, you'll learn about MongoDB Go Driver: Transactions. We cover key concepts, practical examples, and best practices.

MongoDB transactions -- Use session transactions for atomic multi-document operations in replica sets.

The Problem

MongoDB requires replica set for transactions. Without sessions, multi-document operations are not atomic. Use client.StartSession() and WithTransaction.

Wrong

collection.InsertOne(ctx, doc1)
collection.UpdateOne(ctx, filter, update) // If this fails, doc1 still inserted

Output:

// Inconsistent state

Right

session, err := client.StartSession()
defer session.EndSession(ctx)
err = mongo.WithSession(ctx, session, func(sc mongo.SessionContext) error {
    if err := session.StartTransaction(); err != nil { return err }
    if _, err := collection.InsertOne(sc, doc1); err != nil {
        session.AbortTransaction(sc); return err
    }
    if _, err := collection.UpdateOne(sc, filter, update); err != nil {
        session.AbortTransaction(sc); return err
    }
    return session.CommitTransaction(sc)
})

Output:

// Both operations succeed or neither

Prevention

• Start session with client.StartSession()
• Use WithSession and StartTransaction
• AbortTransaction on error
• CommitTransaction on success
• Requires MongoDB 4.0+ replica set

Common Mistakes with mongodb transaction

1. Using foldl instead of foldl' causing stack overflow on large lists
2. Forgetting deriving (Show, Eq) on custom data types needed for debugging
3. Placing the wildcard pattern first in case expressions, making all subsequent patterns unreachable

These mistakes appear frequently in real-world GO code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ

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