Context.Background() vs Context.TODO(): When Should You Use Which?

Background() vs TODO(): Which Context Should You Use?

When migrating code from a global sign package to the go mongo-driver, understanding the appropriate usage of context.TODO() and context.Background() is crucial.

Background()

As per the documentation, context.Background() returns a non-nil, empty Context with the following characteristics:

• Never canceled
• No values
• No deadline

It is commonly used in the main function, initialization, and tests. When no meaningful context is available, context.Background() provides a fallback.

TODO()

context.TODO() also returns a non-nil, empty Context. However, its intended use is specifically when it's unclear which Context to use or when a context is not yet available. By using context.TODO(), you can explicitly document that you need a context but don't currently have a specific one.

Best Practices

• Prefer using the context associated with your HTTP request or other application-specific scenarios.
• Use context.TODO() in situations where there is no clear context available but you still need to indicate that a context is required.
• Avoid using context.Background() outside of main, initialization, or test functions.

Example Usage

Consider the following scenario where an HTTP handler needs to execute a MongoDB query within a specific time limit:

ctx, cancel := context.WithTimeout(r.Context(), 6 * time.Second)
defer cancel()

// ctx automatically times out after 6 seconds
curs, err := c.Find(ctx, bson.M{"some": "filter"})

In this example, context.WithTimeout() creates a new context that derives from the request context (r.Context()). If the MongoDB operation exceeds 6 seconds, the context times out, signaling that the query should be canceled.

Conclusion

Choosing between context.TODO() and context.Background() is a matter of understanding the specific usage scenarios and ensuring that you are providing meaningful and appropriate context to downstream functions.

The above is the detailed content of Context.Background() vs Context.TODO(): When Should You Use Which?. For more information, please follow other related articles on the PHP Chinese website!